| /* Alias analysis for GNU C |
| Copyright (C) 1997, 1998 Free Software Foundation, Inc. |
| Contributed by John Carr (jfc@mit.edu). |
| |
| This file is part of GNU CC. |
| |
| GNU CC is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU CC is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU CC; see the file COPYING. If not, write to |
| the Free Software Foundation, 59 Temple Place - Suite 330, |
| Boston, MA 02111-1307, USA. */ |
| |
| #include "config.h" |
| #include "system.h" |
| #include "rtl.h" |
| #include "expr.h" |
| #include "regs.h" |
| #include "hard-reg-set.h" |
| #include "flags.h" |
| #include "toplev.h" |
| |
| static rtx canon_rtx PROTO((rtx)); |
| static int rtx_equal_for_memref_p PROTO((rtx, rtx)); |
| static rtx find_symbolic_term PROTO((rtx)); |
| static int memrefs_conflict_p PROTO((int, rtx, int, rtx, |
| HOST_WIDE_INT)); |
| static void record_set PROTO((rtx, rtx)); |
| static rtx find_base_term PROTO((rtx)); |
| static int base_alias_check PROTO((rtx, rtx)); |
| static rtx find_base_value PROTO((rtx)); |
| |
| /* Set up all info needed to perform alias analysis on memory references. */ |
| |
| #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X))) |
| |
| /* Perform a basic sanity check. Namely, that there are |
| no alias sets if we're not doing strict aliasing. This helps |
| to catch bugs whereby someone uses PUT_CODE, but doesn't clear |
| MEM_ALIAS_SET, or where a MEM is allocated in some way other |
| than by the use of gen_rtx_MEM, and the MEM_ALIAS_SET is not |
| cleared. */ |
| #ifdef ENABLE_CHECKING |
| #define CHECK_ALIAS_SETS_FOR_CONSISTENCY(MEM1, MEM2) \ |
| (!flag_strict_aliasing \ |
| && (MEM_ALIAS_SET (MEM1) || MEM_ALIAS_SET (MEM2)) \ |
| ? (abort (), 0) : 0) |
| #else |
| #define CHECK_ALIAS_SETS_FOR_CONSISTENCY(MEM1, MEM2) ((void)0) |
| #endif |
| |
| /* Returns nonzero if MEM1 and MEM2 do not alias because they are in |
| different alias sets. */ |
| #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \ |
| (CHECK_ALIAS_SETS_FOR_CONSISTENCY(MEM1, MEM2), \ |
| MEM_ALIAS_SET (MEM1) && MEM_ALIAS_SET (MEM2) \ |
| && MEM_ALIAS_SET (MEM1) != MEM_ALIAS_SET (MEM2)) |
| |
| /* Cap the number of passes we make over the insns propagating alias |
| information through set chains. |
| |
| 10 is a completely arbitrary choice. */ |
| #define MAX_ALIAS_LOOP_PASSES 10 |
| |
| /* reg_base_value[N] gives an address to which register N is related. |
| If all sets after the first add or subtract to the current value |
| or otherwise modify it so it does not point to a different top level |
| object, reg_base_value[N] is equal to the address part of the source |
| of the first set. |
| |
| A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS |
| expressions represent certain special values: function arguments and |
| the stack, frame, and argument pointers. The contents of an address |
| expression are not used (but they are descriptive for debugging); |
| only the address and mode matter. Pointer equality, not rtx_equal_p, |
| determines whether two ADDRESS expressions refer to the same base |
| address. The mode determines whether it is a function argument or |
| other special value. */ |
| |
| rtx *reg_base_value; |
| rtx *new_reg_base_value; |
| unsigned int reg_base_value_size; /* size of reg_base_value array */ |
| #define REG_BASE_VALUE(X) \ |
| (REGNO (X) < reg_base_value_size ? reg_base_value[REGNO (X)] : 0) |
| |
| /* Vector of known invariant relationships between registers. Set in |
| loop unrolling. Indexed by register number, if nonzero the value |
| is an expression describing this register in terms of another. |
| |
| The length of this array is REG_BASE_VALUE_SIZE. |
| |
| Because this array contains only pseudo registers it has no effect |
| after reload. */ |
| static rtx *alias_invariant; |
| |
| /* Vector indexed by N giving the initial (unchanging) value known |
| for pseudo-register N. */ |
| rtx *reg_known_value; |
| |
| /* Indicates number of valid entries in reg_known_value. */ |
| static int reg_known_value_size; |
| |
| /* Vector recording for each reg_known_value whether it is due to a |
| REG_EQUIV note. Future passes (viz., reload) may replace the |
| pseudo with the equivalent expression and so we account for the |
| dependences that would be introduced if that happens. */ |
| /* ??? This is a problem only on the Convex. The REG_EQUIV notes created in |
| assign_parms mention the arg pointer, and there are explicit insns in the |
| RTL that modify the arg pointer. Thus we must ensure that such insns don't |
| get scheduled across each other because that would invalidate the REG_EQUIV |
| notes. One could argue that the REG_EQUIV notes are wrong, but solving |
| the problem in the scheduler will likely give better code, so we do it |
| here. */ |
| char *reg_known_equiv_p; |
| |
| /* True when scanning insns from the start of the rtl to the |
| NOTE_INSN_FUNCTION_BEG note. */ |
| |
| static int copying_arguments; |
| |
| /* Inside SRC, the source of a SET, find a base address. */ |
| |
| static rtx |
| find_base_value (src) |
| register rtx src; |
| { |
| switch (GET_CODE (src)) |
| { |
| case SYMBOL_REF: |
| case LABEL_REF: |
| return src; |
| |
| case REG: |
| /* At the start of a function argument registers have known base |
| values which may be lost later. Returning an ADDRESS |
| expression here allows optimization based on argument values |
| even when the argument registers are used for other purposes. */ |
| if (REGNO (src) < FIRST_PSEUDO_REGISTER && copying_arguments) |
| return new_reg_base_value[REGNO (src)]; |
| |
| /* If a pseudo has a known base value, return it. Do not do this |
| for hard regs since it can result in a circular dependency |
| chain for registers which have values at function entry. |
| |
| The test above is not sufficient because the scheduler may move |
| a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */ |
| if (REGNO (src) >= FIRST_PSEUDO_REGISTER |
| && REGNO (src) < reg_base_value_size |
| && reg_base_value[REGNO (src)]) |
| return reg_base_value[REGNO (src)]; |
| |
| return src; |
| |
| case MEM: |
| /* Check for an argument passed in memory. Only record in the |
| copying-arguments block; it is too hard to track changes |
| otherwise. */ |
| if (copying_arguments |
| && (XEXP (src, 0) == arg_pointer_rtx |
| || (GET_CODE (XEXP (src, 0)) == PLUS |
| && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx))) |
| return gen_rtx_ADDRESS (VOIDmode, src); |
| return 0; |
| |
| case CONST: |
| src = XEXP (src, 0); |
| if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS) |
| break; |
| /* fall through */ |
| |
| case PLUS: |
| case MINUS: |
| { |
| rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1); |
| |
| /* If either operand is a REG, then see if we already have |
| a known value for it. */ |
| if (GET_CODE (src_0) == REG) |
| { |
| temp = find_base_value (src_0); |
| if (temp) |
| src_0 = temp; |
| } |
| |
| if (GET_CODE (src_1) == REG) |
| { |
| temp = find_base_value (src_1); |
| if (temp) |
| src_1 = temp; |
| } |
| |
| /* Guess which operand is the base address. |
| |
| If either operand is a symbol, then it is the base. If |
| either operand is a CONST_INT, then the other is the base. */ |
| |
| if (GET_CODE (src_1) == CONST_INT |
| || GET_CODE (src_0) == SYMBOL_REF |
| || GET_CODE (src_0) == LABEL_REF |
| || GET_CODE (src_0) == CONST) |
| return find_base_value (src_0); |
| |
| if (GET_CODE (src_0) == CONST_INT |
| || GET_CODE (src_1) == SYMBOL_REF |
| || GET_CODE (src_1) == LABEL_REF |
| || GET_CODE (src_1) == CONST) |
| return find_base_value (src_1); |
| |
| /* This might not be necessary anymore. |
| |
| If either operand is a REG that is a known pointer, then it |
| is the base. */ |
| if (GET_CODE (src_0) == REG && REGNO_POINTER_FLAG (REGNO (src_0))) |
| return find_base_value (src_0); |
| |
| if (GET_CODE (src_1) == REG && REGNO_POINTER_FLAG (REGNO (src_1))) |
| return find_base_value (src_1); |
| |
| return 0; |
| } |
| |
| case LO_SUM: |
| /* The standard form is (lo_sum reg sym) so look only at the |
| second operand. */ |
| return find_base_value (XEXP (src, 1)); |
| |
| case AND: |
| /* If the second operand is constant set the base |
| address to the first operand. */ |
| if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0) |
| return find_base_value (XEXP (src, 0)); |
| return 0; |
| |
| case ZERO_EXTEND: |
| case SIGN_EXTEND: /* used for NT/Alpha pointers */ |
| case HIGH: |
| return find_base_value (XEXP (src, 0)); |
| |
| default: |
| break; |
| } |
| |
| return 0; |
| } |
| |
| /* Called from init_alias_analysis indirectly through note_stores. */ |
| |
| /* while scanning insns to find base values, reg_seen[N] is nonzero if |
| register N has been set in this function. */ |
| static char *reg_seen; |
| |
| /* Addresses which are known not to alias anything else are identified |
| by a unique integer. */ |
| static int unique_id; |
| |
| static void |
| record_set (dest, set) |
| rtx dest, set; |
| { |
| register int regno; |
| rtx src; |
| |
| if (GET_CODE (dest) != REG) |
| return; |
| |
| regno = REGNO (dest); |
| |
| if (set) |
| { |
| /* A CLOBBER wipes out any old value but does not prevent a previously |
| unset register from acquiring a base address (i.e. reg_seen is not |
| set). */ |
| if (GET_CODE (set) == CLOBBER) |
| { |
| new_reg_base_value[regno] = 0; |
| return; |
| } |
| src = SET_SRC (set); |
| } |
| else |
| { |
| if (reg_seen[regno]) |
| { |
| new_reg_base_value[regno] = 0; |
| return; |
| } |
| reg_seen[regno] = 1; |
| new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode, |
| GEN_INT (unique_id++)); |
| return; |
| } |
| |
| /* This is not the first set. If the new value is not related to the |
| old value, forget the base value. Note that the following code is |
| not detected: |
| extern int x, y; int *p = &x; p += (&y-&x); |
| ANSI C does not allow computing the difference of addresses |
| of distinct top level objects. */ |
| if (new_reg_base_value[regno]) |
| switch (GET_CODE (src)) |
| { |
| case LO_SUM: |
| case PLUS: |
| case MINUS: |
| if (XEXP (src, 0) != dest && XEXP (src, 1) != dest) |
| new_reg_base_value[regno] = 0; |
| break; |
| case AND: |
| if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT) |
| new_reg_base_value[regno] = 0; |
| break; |
| default: |
| new_reg_base_value[regno] = 0; |
| break; |
| } |
| /* If this is the first set of a register, record the value. */ |
| else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno]) |
| && ! reg_seen[regno] && new_reg_base_value[regno] == 0) |
| new_reg_base_value[regno] = find_base_value (src); |
| |
| reg_seen[regno] = 1; |
| } |
| |
| /* Called from loop optimization when a new pseudo-register is created. */ |
| void |
| record_base_value (regno, val, invariant) |
| int regno; |
| rtx val; |
| int invariant; |
| { |
| if (regno >= reg_base_value_size) |
| return; |
| |
| /* If INVARIANT is true then this value also describes an invariant |
| relationship which can be used to deduce that two registers with |
| unknown values are different. */ |
| if (invariant && alias_invariant) |
| alias_invariant[regno] = val; |
| |
| if (GET_CODE (val) == REG) |
| { |
| if (REGNO (val) < reg_base_value_size) |
| { |
| reg_base_value[regno] = reg_base_value[REGNO (val)]; |
| } |
| return; |
| } |
| reg_base_value[regno] = find_base_value (val); |
| } |
| |
| static rtx |
| canon_rtx (x) |
| rtx x; |
| { |
| /* Recursively look for equivalences. */ |
| if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER |
| && REGNO (x) < reg_known_value_size) |
| return reg_known_value[REGNO (x)] == x |
| ? x : canon_rtx (reg_known_value[REGNO (x)]); |
| else if (GET_CODE (x) == PLUS) |
| { |
| rtx x0 = canon_rtx (XEXP (x, 0)); |
| rtx x1 = canon_rtx (XEXP (x, 1)); |
| |
| if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1)) |
| { |
| /* We can tolerate LO_SUMs being offset here; these |
| rtl are used for nothing other than comparisons. */ |
| if (GET_CODE (x0) == CONST_INT) |
| return plus_constant_for_output (x1, INTVAL (x0)); |
| else if (GET_CODE (x1) == CONST_INT) |
| return plus_constant_for_output (x0, INTVAL (x1)); |
| return gen_rtx_PLUS (GET_MODE (x), x0, x1); |
| } |
| } |
| /* This gives us much better alias analysis when called from |
| the loop optimizer. Note we want to leave the original |
| MEM alone, but need to return the canonicalized MEM with |
| all the flags with their original values. */ |
| else if (GET_CODE (x) == MEM) |
| { |
| rtx addr = canon_rtx (XEXP (x, 0)); |
| if (addr != XEXP (x, 0)) |
| { |
| rtx new = gen_rtx_MEM (GET_MODE (x), addr); |
| MEM_VOLATILE_P (new) = MEM_VOLATILE_P (x); |
| RTX_UNCHANGING_P (new) = RTX_UNCHANGING_P (x); |
| MEM_IN_STRUCT_P (new) = MEM_IN_STRUCT_P (x); |
| MEM_ALIAS_SET (new) = MEM_ALIAS_SET (x); |
| x = new; |
| } |
| } |
| return x; |
| } |
| |
| /* Return 1 if X and Y are identical-looking rtx's. |
| |
| We use the data in reg_known_value above to see if two registers with |
| different numbers are, in fact, equivalent. */ |
| |
| static int |
| rtx_equal_for_memref_p (x, y) |
| rtx x, y; |
| { |
| register int i; |
| register int j; |
| register enum rtx_code code; |
| register char *fmt; |
| |
| if (x == 0 && y == 0) |
| return 1; |
| if (x == 0 || y == 0) |
| return 0; |
| x = canon_rtx (x); |
| y = canon_rtx (y); |
| |
| if (x == y) |
| return 1; |
| |
| code = GET_CODE (x); |
| /* Rtx's of different codes cannot be equal. */ |
| if (code != GET_CODE (y)) |
| return 0; |
| |
| /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. |
| (REG:SI x) and (REG:HI x) are NOT equivalent. */ |
| |
| if (GET_MODE (x) != GET_MODE (y)) |
| return 0; |
| |
| /* REG, LABEL_REF, and SYMBOL_REF can be compared nonrecursively. */ |
| |
| if (code == REG) |
| return REGNO (x) == REGNO (y); |
| if (code == LABEL_REF) |
| return XEXP (x, 0) == XEXP (y, 0); |
| if (code == SYMBOL_REF) |
| return XSTR (x, 0) == XSTR (y, 0); |
| if (code == CONST_INT) |
| return INTVAL (x) == INTVAL (y); |
| if (code == ADDRESSOF) |
| return REGNO (XEXP (x, 0)) == REGNO (XEXP (y, 0)) && XINT (x, 1) == XINT (y, 1); |
| |
| /* For commutative operations, the RTX match if the operand match in any |
| order. Also handle the simple binary and unary cases without a loop. */ |
| if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c') |
| return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)) |
| && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1))) |
| || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1)) |
| && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0)))); |
| else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2') |
| return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)) |
| && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1))); |
| else if (GET_RTX_CLASS (code) == '1') |
| return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)); |
| |
| /* Compare the elements. If any pair of corresponding elements |
| fail to match, return 0 for the whole things. |
| |
| Limit cases to types which actually appear in addresses. */ |
| |
| fmt = GET_RTX_FORMAT (code); |
| for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) |
| { |
| switch (fmt[i]) |
| { |
| case 'i': |
| if (XINT (x, i) != XINT (y, i)) |
| return 0; |
| break; |
| |
| case 'E': |
| /* Two vectors must have the same length. */ |
| if (XVECLEN (x, i) != XVECLEN (y, i)) |
| return 0; |
| |
| /* And the corresponding elements must match. */ |
| for (j = 0; j < XVECLEN (x, i); j++) |
| if (rtx_equal_for_memref_p (XVECEXP (x, i, j), XVECEXP (y, i, j)) == 0) |
| return 0; |
| break; |
| |
| case 'e': |
| if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0) |
| return 0; |
| break; |
| |
| /* This can happen for an asm which clobbers memory. */ |
| case '0': |
| break; |
| |
| /* It is believed that rtx's at this level will never |
| contain anything but integers and other rtx's, |
| except for within LABEL_REFs and SYMBOL_REFs. */ |
| default: |
| abort (); |
| } |
| } |
| return 1; |
| } |
| |
| /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within |
| X and return it, or return 0 if none found. */ |
| |
| static rtx |
| find_symbolic_term (x) |
| rtx x; |
| { |
| register int i; |
| register enum rtx_code code; |
| register char *fmt; |
| |
| code = GET_CODE (x); |
| if (code == SYMBOL_REF || code == LABEL_REF) |
| return x; |
| if (GET_RTX_CLASS (code) == 'o') |
| return 0; |
| |
| fmt = GET_RTX_FORMAT (code); |
| for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) |
| { |
| rtx t; |
| |
| if (fmt[i] == 'e') |
| { |
| t = find_symbolic_term (XEXP (x, i)); |
| if (t != 0) |
| return t; |
| } |
| else if (fmt[i] == 'E') |
| break; |
| } |
| return 0; |
| } |
| |
| static rtx |
| find_base_term (x) |
| register rtx x; |
| { |
| switch (GET_CODE (x)) |
| { |
| case REG: |
| return REG_BASE_VALUE (x); |
| |
| case ZERO_EXTEND: |
| case SIGN_EXTEND: /* Used for Alpha/NT pointers */ |
| case HIGH: |
| case PRE_INC: |
| case PRE_DEC: |
| case POST_INC: |
| case POST_DEC: |
| return find_base_term (XEXP (x, 0)); |
| |
| case CONST: |
| x = XEXP (x, 0); |
| if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS) |
| return 0; |
| /* fall through */ |
| case LO_SUM: |
| case PLUS: |
| case MINUS: |
| { |
| rtx tmp = find_base_term (XEXP (x, 0)); |
| if (tmp) |
| return tmp; |
| return find_base_term (XEXP (x, 1)); |
| } |
| |
| case AND: |
| if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT) |
| return REG_BASE_VALUE (XEXP (x, 0)); |
| return 0; |
| |
| case SYMBOL_REF: |
| case LABEL_REF: |
| return x; |
| |
| default: |
| return 0; |
| } |
| } |
| |
| /* Return 0 if the addresses X and Y are known to point to different |
| objects, 1 if they might be pointers to the same object. */ |
| |
| static int |
| base_alias_check (x, y) |
| rtx x, y; |
| { |
| rtx x_base = find_base_term (x); |
| rtx y_base = find_base_term (y); |
| |
| /* If the address itself has no known base see if a known equivalent |
| value has one. If either address still has no known base, nothing |
| is known about aliasing. */ |
| if (x_base == 0) |
| { |
| rtx x_c; |
| if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x) |
| return 1; |
| x_base = find_base_term (x_c); |
| if (x_base == 0) |
| return 1; |
| } |
| |
| if (y_base == 0) |
| { |
| rtx y_c; |
| if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y) |
| return 1; |
| y_base = find_base_term (y_c); |
| if (y_base == 0) |
| return 1; |
| } |
| |
| /* If the base addresses are equal nothing is known about aliasing. */ |
| if (rtx_equal_p (x_base, y_base)) |
| return 1; |
| |
| /* The base addresses of the read and write are different |
| expressions. If they are both symbols and they are not accessed |
| via AND, there is no conflict. */ |
| /* XXX: We can bring knowledge of object alignment and offset into |
| play here. For example, on alpha, "char a, b;" can alias one |
| another, though "char a; long b;" cannot. Similarly, offsets |
| into strutures may be brought into play. Given "char a, b[40];", |
| a and b[1] may overlap, but a and b[20] do not. */ |
| if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS) |
| { |
| return GET_CODE (x) == AND || GET_CODE (y) == AND; |
| } |
| |
| /* If one address is a stack reference there can be no alias: |
| stack references using different base registers do not alias, |
| a stack reference can not alias a parameter, and a stack reference |
| can not alias a global. */ |
| if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode) |
| || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode)) |
| return 0; |
| |
| if (! flag_argument_noalias) |
| return 1; |
| |
| if (flag_argument_noalias > 1) |
| return 0; |
| |
| /* Weak noalias assertion (arguments are distinct, but may match globals). */ |
| return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode); |
| } |
| |
| /* Return nonzero if X and Y (memory addresses) could reference the |
| same location in memory. C is an offset accumulator. When |
| C is nonzero, we are testing aliases between X and Y + C. |
| XSIZE is the size in bytes of the X reference, |
| similarly YSIZE is the size in bytes for Y. |
| |
| If XSIZE or YSIZE is zero, we do not know the amount of memory being |
| referenced (the reference was BLKmode), so make the most pessimistic |
| assumptions. |
| |
| If XSIZE or YSIZE is negative, we may access memory outside the object |
| being referenced as a side effect. This can happen when using AND to |
| align memory references, as is done on the Alpha. |
| |
| Nice to notice that varying addresses cannot conflict with fp if no |
| local variables had their addresses taken, but that's too hard now. */ |
| |
| |
| static int |
| memrefs_conflict_p (xsize, x, ysize, y, c) |
| register rtx x, y; |
| int xsize, ysize; |
| HOST_WIDE_INT c; |
| { |
| if (GET_CODE (x) == HIGH) |
| x = XEXP (x, 0); |
| else if (GET_CODE (x) == LO_SUM) |
| x = XEXP (x, 1); |
| else |
| x = canon_rtx (x); |
| if (GET_CODE (y) == HIGH) |
| y = XEXP (y, 0); |
| else if (GET_CODE (y) == LO_SUM) |
| y = XEXP (y, 1); |
| else |
| y = canon_rtx (y); |
| |
| if (rtx_equal_for_memref_p (x, y)) |
| { |
| if (xsize <= 0 || ysize <= 0) |
| return 1; |
| if (c >= 0 && xsize > c) |
| return 1; |
| if (c < 0 && ysize+c > 0) |
| return 1; |
| return 0; |
| } |
| |
| /* This code used to check for conflicts involving stack references and |
| globals but the base address alias code now handles these cases. */ |
| |
| if (GET_CODE (x) == PLUS) |
| { |
| /* The fact that X is canonicalized means that this |
| PLUS rtx is canonicalized. */ |
| rtx x0 = XEXP (x, 0); |
| rtx x1 = XEXP (x, 1); |
| |
| if (GET_CODE (y) == PLUS) |
| { |
| /* The fact that Y is canonicalized means that this |
| PLUS rtx is canonicalized. */ |
| rtx y0 = XEXP (y, 0); |
| rtx y1 = XEXP (y, 1); |
| |
| if (rtx_equal_for_memref_p (x1, y1)) |
| return memrefs_conflict_p (xsize, x0, ysize, y0, c); |
| if (rtx_equal_for_memref_p (x0, y0)) |
| return memrefs_conflict_p (xsize, x1, ysize, y1, c); |
| if (GET_CODE (x1) == CONST_INT) |
| if (GET_CODE (y1) == CONST_INT) |
| return memrefs_conflict_p (xsize, x0, ysize, y0, |
| c - INTVAL (x1) + INTVAL (y1)); |
| else |
| return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1)); |
| else if (GET_CODE (y1) == CONST_INT) |
| return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1)); |
| |
| return 1; |
| } |
| else if (GET_CODE (x1) == CONST_INT) |
| return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1)); |
| } |
| else if (GET_CODE (y) == PLUS) |
| { |
| /* The fact that Y is canonicalized means that this |
| PLUS rtx is canonicalized. */ |
| rtx y0 = XEXP (y, 0); |
| rtx y1 = XEXP (y, 1); |
| |
| if (GET_CODE (y1) == CONST_INT) |
| return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1)); |
| else |
| return 1; |
| } |
| |
| if (GET_CODE (x) == GET_CODE (y)) |
| switch (GET_CODE (x)) |
| { |
| case MULT: |
| { |
| /* Handle cases where we expect the second operands to be the |
| same, and check only whether the first operand would conflict |
| or not. */ |
| rtx x0, y0; |
| rtx x1 = canon_rtx (XEXP (x, 1)); |
| rtx y1 = canon_rtx (XEXP (y, 1)); |
| if (! rtx_equal_for_memref_p (x1, y1)) |
| return 1; |
| x0 = canon_rtx (XEXP (x, 0)); |
| y0 = canon_rtx (XEXP (y, 0)); |
| if (rtx_equal_for_memref_p (x0, y0)) |
| return (xsize == 0 || ysize == 0 |
| || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)); |
| |
| /* Can't properly adjust our sizes. */ |
| if (GET_CODE (x1) != CONST_INT) |
| return 1; |
| xsize /= INTVAL (x1); |
| ysize /= INTVAL (x1); |
| c /= INTVAL (x1); |
| return memrefs_conflict_p (xsize, x0, ysize, y0, c); |
| } |
| |
| case REG: |
| /* Are these registers known not to be equal? */ |
| if (alias_invariant) |
| { |
| int r_x = REGNO (x), r_y = REGNO (y); |
| rtx i_x, i_y; /* invariant relationships of X and Y */ |
| |
| i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x]; |
| i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y]; |
| |
| if (i_x == 0 && i_y == 0) |
| break; |
| |
| if (! memrefs_conflict_p (xsize, i_x ? i_x : x, |
| ysize, i_y ? i_y : y, c)) |
| return 0; |
| } |
| break; |
| |
| default: |
| break; |
| } |
| |
| /* Treat an access through an AND (e.g. a subword access on an Alpha) |
| as an access with indeterminate size. |
| ??? Could instead convert an n byte reference at (and x y) to an |
| n-y byte reference at (plus x y). */ |
| if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT) |
| return memrefs_conflict_p (-1, XEXP (x, 0), ysize, y, c); |
| if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT) |
| { |
| /* XXX: If we are indexing far enough into the array/structure, we |
| may yet be able to determine that we can not overlap. But we |
| also need to that we are far enough from the end not to overlap |
| a following reference, so we do nothing for now. */ |
| return memrefs_conflict_p (xsize, x, -1, XEXP (y, 0), c); |
| } |
| |
| if (CONSTANT_P (x)) |
| { |
| if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT) |
| { |
| c += (INTVAL (y) - INTVAL (x)); |
| return (xsize <= 0 || ysize <= 0 |
| || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)); |
| } |
| |
| if (GET_CODE (x) == CONST) |
| { |
| if (GET_CODE (y) == CONST) |
| return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), |
| ysize, canon_rtx (XEXP (y, 0)), c); |
| else |
| return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), |
| ysize, y, c); |
| } |
| if (GET_CODE (y) == CONST) |
| return memrefs_conflict_p (xsize, x, ysize, |
| canon_rtx (XEXP (y, 0)), c); |
| |
| if (CONSTANT_P (y)) |
| return (xsize < 0 || ysize < 0 |
| || (rtx_equal_for_memref_p (x, y) |
| && (xsize == 0 || ysize == 0 |
| || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)))); |
| |
| return 1; |
| } |
| return 1; |
| } |
| |
| /* Functions to compute memory dependencies. |
| |
| Since we process the insns in execution order, we can build tables |
| to keep track of what registers are fixed (and not aliased), what registers |
| are varying in known ways, and what registers are varying in unknown |
| ways. |
| |
| If both memory references are volatile, then there must always be a |
| dependence between the two references, since their order can not be |
| changed. A volatile and non-volatile reference can be interchanged |
| though. |
| |
| A MEM_IN_STRUCT reference at a non-QImode non-AND varying address can never |
| conflict with a non-MEM_IN_STRUCT reference at a fixed address. We must |
| allow QImode aliasing because the ANSI C standard allows character |
| pointers to alias anything. We are assuming that characters are |
| always QImode here. We also must allow AND addresses, because they may |
| generate accesses outside the object being referenced. This is used to |
| generate aligned addresses from unaligned addresses, for instance, the |
| alpha storeqi_unaligned pattern. */ |
| |
| /* Read dependence: X is read after read in MEM takes place. There can |
| only be a dependence here if both reads are volatile. */ |
| |
| int |
| read_dependence (mem, x) |
| rtx mem; |
| rtx x; |
| { |
| return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem); |
| } |
| |
| /* True dependence: X is read after store in MEM takes place. */ |
| |
| int |
| true_dependence (mem, mem_mode, x, varies) |
| rtx mem; |
| enum machine_mode mem_mode; |
| rtx x; |
| int (*varies) PROTO((rtx)); |
| { |
| register rtx x_addr, mem_addr; |
| |
| if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) |
| return 1; |
| |
| if (DIFFERENT_ALIAS_SETS_P (x, mem)) |
| return 0; |
| |
| /* If X is an unchanging read, then it can't possibly conflict with any |
| non-unchanging store. It may conflict with an unchanging write though, |
| because there may be a single store to this address to initialize it. |
| Just fall through to the code below to resolve the case where we have |
| both an unchanging read and an unchanging write. This won't handle all |
| cases optimally, but the possible performance loss should be |
| negligible. */ |
| if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem)) |
| return 0; |
| |
| if (! base_alias_check (XEXP (x, 0), XEXP (mem, 0))) |
| return 0; |
| |
| x_addr = canon_rtx (XEXP (x, 0)); |
| mem_addr = canon_rtx (XEXP (mem, 0)); |
| |
| if (mem_mode == VOIDmode) |
| mem_mode = GET_MODE (mem); |
| |
| if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr, |
| SIZE_FOR_MODE (x), x_addr, 0)) |
| return 0; |
| |
| /* If both references are struct references, or both are not, nothing |
| is known about aliasing. |
| |
| If either reference is QImode or BLKmode, ANSI C permits aliasing. |
| |
| If both addresses are constant, or both are not, nothing is known |
| about aliasing. */ |
| if (MEM_IN_STRUCT_P (x) == MEM_IN_STRUCT_P (mem) |
| || mem_mode == QImode || mem_mode == BLKmode |
| || GET_MODE (x) == QImode || GET_MODE (x) == BLKmode |
| || GET_CODE (x_addr) == AND || GET_CODE (mem_addr) == AND |
| || varies (x_addr) == varies (mem_addr)) |
| return 1; |
| |
| /* One memory reference is to a constant address, one is not. |
| One is to a structure, the other is not. |
| |
| If either memory reference is a variable structure the other is a |
| fixed scalar and there is no aliasing. */ |
| if ((MEM_IN_STRUCT_P (mem) && varies (mem_addr)) |
| || (MEM_IN_STRUCT_P (x) && varies (x_addr))) |
| return 0; |
| |
| return 1; |
| } |
| |
| /* Anti dependence: X is written after read in MEM takes place. */ |
| |
| int |
| anti_dependence (mem, x) |
| rtx mem; |
| rtx x; |
| { |
| rtx x_addr, mem_addr; |
| |
| if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) |
| return 1; |
| |
| /* If MEM is an unchanging read, then it can't possibly conflict with |
| the store to X, because there is at most one store to MEM, and it must |
| have occurred somewhere before MEM. */ |
| if (RTX_UNCHANGING_P (mem)) |
| return 0; |
| |
| if (! base_alias_check (XEXP (x, 0), XEXP (mem, 0))) |
| return 0; |
| |
| x = canon_rtx (x); |
| mem = canon_rtx (mem); |
| |
| if (DIFFERENT_ALIAS_SETS_P (x, mem)) |
| return 0; |
| |
| x_addr = XEXP (x, 0); |
| mem_addr = XEXP (mem, 0); |
| |
| return (memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr, |
| SIZE_FOR_MODE (x), x_addr, 0) |
| && ! (MEM_IN_STRUCT_P (mem) && rtx_addr_varies_p (mem) |
| && GET_MODE (mem) != QImode |
| && GET_CODE (mem_addr) != AND |
| && ! MEM_IN_STRUCT_P (x) && ! rtx_addr_varies_p (x)) |
| && ! (MEM_IN_STRUCT_P (x) && rtx_addr_varies_p (x) |
| && GET_MODE (x) != QImode |
| && GET_CODE (x_addr) != AND |
| && ! MEM_IN_STRUCT_P (mem) && ! rtx_addr_varies_p (mem))); |
| } |
| |
| /* Output dependence: X is written after store in MEM takes place. */ |
| |
| int |
| output_dependence (mem, x) |
| register rtx mem; |
| register rtx x; |
| { |
| if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) |
| return 1; |
| |
| if (! base_alias_check (XEXP (x, 0), XEXP (mem, 0))) |
| return 0; |
| |
| x = canon_rtx (x); |
| mem = canon_rtx (mem); |
| |
| if (DIFFERENT_ALIAS_SETS_P (x, mem)) |
| return 0; |
| |
| return (memrefs_conflict_p (SIZE_FOR_MODE (mem), XEXP (mem, 0), |
| SIZE_FOR_MODE (x), XEXP (x, 0), 0) |
| && ! (MEM_IN_STRUCT_P (mem) && rtx_addr_varies_p (mem) |
| && GET_MODE (mem) != QImode |
| && GET_CODE (XEXP (mem, 0)) != AND |
| && ! MEM_IN_STRUCT_P (x) && ! rtx_addr_varies_p (x)) |
| && ! (MEM_IN_STRUCT_P (x) && rtx_addr_varies_p (x) |
| && GET_MODE (x) != QImode |
| && GET_CODE (XEXP (x, 0)) != AND |
| && ! MEM_IN_STRUCT_P (mem) && ! rtx_addr_varies_p (mem))); |
| } |
| |
| |
| static HARD_REG_SET argument_registers; |
| |
| void |
| init_alias_once () |
| { |
| register int i; |
| |
| #ifndef OUTGOING_REGNO |
| #define OUTGOING_REGNO(N) N |
| #endif |
| for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) |
| /* Check whether this register can hold an incoming pointer |
| argument. FUNCTION_ARG_REGNO_P tests outgoing register |
| numbers, so translate if necessary due to register windows. */ |
| if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i)) |
| && HARD_REGNO_MODE_OK (i, Pmode)) |
| SET_HARD_REG_BIT (argument_registers, i); |
| } |
| |
| void |
| init_alias_analysis () |
| { |
| int maxreg = max_reg_num (); |
| int changed, pass; |
| register int i; |
| register rtx insn; |
| |
| reg_known_value_size = maxreg; |
| |
| reg_known_value |
| = (rtx *) oballoc ((maxreg - FIRST_PSEUDO_REGISTER) * sizeof (rtx)) |
| - FIRST_PSEUDO_REGISTER; |
| reg_known_equiv_p = |
| oballoc (maxreg - FIRST_PSEUDO_REGISTER) - FIRST_PSEUDO_REGISTER; |
| bzero ((char *) (reg_known_value + FIRST_PSEUDO_REGISTER), |
| (maxreg-FIRST_PSEUDO_REGISTER) * sizeof (rtx)); |
| bzero (reg_known_equiv_p + FIRST_PSEUDO_REGISTER, |
| (maxreg - FIRST_PSEUDO_REGISTER) * sizeof (char)); |
| |
| /* Overallocate reg_base_value to allow some growth during loop |
| optimization. Loop unrolling can create a large number of |
| registers. */ |
| reg_base_value_size = maxreg * 2; |
| reg_base_value = (rtx *)oballoc (reg_base_value_size * sizeof (rtx)); |
| new_reg_base_value = (rtx *)alloca (reg_base_value_size * sizeof (rtx)); |
| reg_seen = (char *)alloca (reg_base_value_size); |
| bzero ((char *) reg_base_value, reg_base_value_size * sizeof (rtx)); |
| if (! reload_completed && flag_unroll_loops) |
| { |
| alias_invariant = (rtx *)xrealloc (alias_invariant, |
| reg_base_value_size * sizeof (rtx)); |
| bzero ((char *)alias_invariant, reg_base_value_size * sizeof (rtx)); |
| } |
| |
| |
| /* The basic idea is that each pass through this loop will use the |
| "constant" information from the previous pass to propagate alias |
| information through another level of assignments. |
| |
| This could get expensive if the assignment chains are long. Maybe |
| we should throttle the number of iterations, possibly based on |
| the optimization level or flag_expensive_optimizations. |
| |
| We could propagate more information in the first pass by making use |
| of REG_N_SETS to determine immediately that the alias information |
| for a pseudo is "constant". |
| |
| A program with an uninitialized variable can cause an infinite loop |
| here. Instead of doing a full dataflow analysis to detect such problems |
| we just cap the number of iterations for the loop. |
| |
| The state of the arrays for the set chain in question does not matter |
| since the program has undefined behavior. */ |
| |
| pass = 0; |
| do |
| { |
| /* Assume nothing will change this iteration of the loop. */ |
| changed = 0; |
| |
| /* We want to assign the same IDs each iteration of this loop, so |
| start counting from zero each iteration of the loop. */ |
| unique_id = 0; |
| |
| /* We're at the start of the funtion each iteration through the |
| loop, so we're copying arguments. */ |
| copying_arguments = 1; |
| |
| /* Wipe the potential alias information clean for this pass. */ |
| bzero ((char *) new_reg_base_value, reg_base_value_size * sizeof (rtx)); |
| |
| /* Wipe the reg_seen array clean. */ |
| bzero ((char *) reg_seen, reg_base_value_size); |
| |
| /* Mark all hard registers which may contain an address. |
| The stack, frame and argument pointers may contain an address. |
| An argument register which can hold a Pmode value may contain |
| an address even if it is not in BASE_REGS. |
| |
| The address expression is VOIDmode for an argument and |
| Pmode for other registers. */ |
| |
| for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) |
| if (TEST_HARD_REG_BIT (argument_registers, i)) |
| new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode, |
| gen_rtx_REG (Pmode, i)); |
| |
| new_reg_base_value[STACK_POINTER_REGNUM] |
| = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx); |
| new_reg_base_value[ARG_POINTER_REGNUM] |
| = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx); |
| new_reg_base_value[FRAME_POINTER_REGNUM] |
| = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx); |
| #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM |
| new_reg_base_value[HARD_FRAME_POINTER_REGNUM] |
| = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx); |
| #endif |
| if (struct_value_incoming_rtx |
| && GET_CODE (struct_value_incoming_rtx) == REG) |
| new_reg_base_value[REGNO (struct_value_incoming_rtx)] |
| = gen_rtx_ADDRESS (Pmode, struct_value_incoming_rtx); |
| |
| if (static_chain_rtx |
| && GET_CODE (static_chain_rtx) == REG) |
| new_reg_base_value[REGNO (static_chain_rtx)] |
| = gen_rtx_ADDRESS (Pmode, static_chain_rtx); |
| |
| /* Walk the insns adding values to the new_reg_base_value array. */ |
| for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) |
| { |
| if (GET_RTX_CLASS (GET_CODE (insn)) == 'i') |
| { |
| rtx note, set; |
| /* If this insn has a noalias note, process it, Otherwise, |
| scan for sets. A simple set will have no side effects |
| which could change the base value of any other register. */ |
| |
| if (GET_CODE (PATTERN (insn)) == SET |
| && (find_reg_note (insn, REG_NOALIAS, NULL_RTX))) |
| record_set (SET_DEST (PATTERN (insn)), NULL_RTX); |
| else |
| note_stores (PATTERN (insn), record_set); |
| |
| set = single_set (insn); |
| |
| if (set != 0 |
| && GET_CODE (SET_DEST (set)) == REG |
| && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER |
| && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0 |
| && REG_N_SETS (REGNO (SET_DEST (set))) == 1) |
| || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0) |
| && GET_CODE (XEXP (note, 0)) != EXPR_LIST) |
| { |
| int regno = REGNO (SET_DEST (set)); |
| reg_known_value[regno] = XEXP (note, 0); |
| reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV; |
| } |
| } |
| else if (GET_CODE (insn) == NOTE |
| && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG) |
| copying_arguments = 0; |
| } |
| |
| /* Now propagate values from new_reg_base_value to reg_base_value. */ |
| for (i = 0; i < reg_base_value_size; i++) |
| { |
| if (new_reg_base_value[i] |
| && new_reg_base_value[i] != reg_base_value[i] |
| && ! rtx_equal_p (new_reg_base_value[i], reg_base_value[i])) |
| { |
| reg_base_value[i] = new_reg_base_value[i]; |
| changed = 1; |
| } |
| } |
| } |
| while (changed && ++pass < MAX_ALIAS_LOOP_PASSES); |
| |
| /* Fill in the remaining entries. */ |
| for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++) |
| if (reg_known_value[i] == 0) |
| reg_known_value[i] = regno_reg_rtx[i]; |
| |
| /* Simplify the reg_base_value array so that no register refers to |
| another register, except to special registers indirectly through |
| ADDRESS expressions. |
| |
| In theory this loop can take as long as O(registers^2), but unless |
| there are very long dependency chains it will run in close to linear |
| time. |
| |
| This loop may not be needed any longer now that the main loop does |
| a better job at propagating alias information. */ |
| pass = 0; |
| do |
| { |
| changed = 0; |
| pass++; |
| for (i = 0; i < reg_base_value_size; i++) |
| { |
| rtx base = reg_base_value[i]; |
| if (base && GET_CODE (base) == REG) |
| { |
| int base_regno = REGNO (base); |
| if (base_regno == i) /* register set from itself */ |
| reg_base_value[i] = 0; |
| else |
| reg_base_value[i] = reg_base_value[base_regno]; |
| changed = 1; |
| } |
| } |
| } |
| while (changed && pass < MAX_ALIAS_LOOP_PASSES); |
| |
| new_reg_base_value = 0; |
| reg_seen = 0; |
| } |
| |
| void |
| end_alias_analysis () |
| { |
| reg_known_value = 0; |
| reg_base_value = 0; |
| reg_base_value_size = 0; |
| if (alias_invariant) |
| { |
| free ((char *)alias_invariant); |
| alias_invariant = 0; |
| } |
| } |