tree 7d8ae0764e0b46a32a6444af40917e7e457206f4
parent 02e2e15ec4b610c0f5c73e1db424b1bbc65dd39a
author Roger Sayle <roger@nextmovesoftware.com> 1657040773 +0100
committer Roger Sayle <roger@nextmovesoftware.com> 1657040773 +0100

Doubleword version of and;cmp to not;test optimization on x86.

This patch extends the earlier and;cmp to not;test optimization to also
perform this transformation for TImode on TARGET_64BIT and DImode on -m32,
One motivation for this is that it's a step to fixing the current failure
of gcc.target/i386/pr65105-5.c on -m32.

A more direct benefit for x86_64 is that the following code:

int foo(__int128 x, __int128 y)
{
  return (x & y) == y;
}

improves with -O2 from 15 instructions:

        movq    %rdi, %r8
        movq    %rsi, %rax
        movq    %rax, %rdi
        movq    %r8, %rsi
        movq    %rdx, %r8
        andq    %rdx, %rsi
        andq    %rcx, %rdi
        movq    %rsi, %rax
        movq    %rdi, %rdx
        xorq    %r8, %rax
        xorq    %rcx, %rdx
        orq     %rdx, %rax
        sete    %al
        movzbl  %al, %eax
        ret

to the slightly better 13 instructions:

        movq    %rdi, %r8
        movq    %rsi, %rax
        movq    %r8, %rsi
        movq    %rax, %rdi
        notq    %rsi
        notq    %rdi
        andq    %rdx, %rsi
        andq    %rcx, %rdi
        movq    %rsi, %rax
        orq     %rdi, %rax
        sete    %al
        movzbl  %al, %eax
        ret

2022-07-05  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/i386/i386.cc (ix86_rtx_costs) <COMPARE>: Provide costs
	for double word comparisons and tests (comparisons against zero).
	* config/i386/i386.md (*test<mode>_not_doubleword): Split DWI
	and;cmp into andn;cmp $0 as a pre-reload splitter.
	(*andn<dwi>3_doubleword_bmi): Use <dwi> instead of <mode> in name.
	(*<any_or><dwi>3_doubleword): Likewise.

gcc/testsuite/ChangeLog
	* gcc.target/i386/testnot-3.c: New test case.