gnu /
gcc /
63e1b2e767a3f4695373c2406ff719c0a60c1858 rtl: Try to remove EH edges after {pro,epi}logue generation [PR90259]
After prologue and epilogue generation, the judgement on whether
one memory access onto stack frame may trap or not could change,
since we get more exact stack information by now.
As PR90259 shows, some memory access becomes impossible to trap
any more after prologue and epilogue generation, it can make
subsequent optimization be able to remove it if safe, but it
results in unexpected control flow status due to REG_EH_REGION
note missing.
This patch proposes to try to remove EH edges with function
purge_all_dead_edges after prologue and epilogue generation,
it simplifies CFG as early as we can and don't need any fixup
in downstream passes.
CFG simplification result with PR90259's case as example:
*before*
18: %1:TF=call [`__gcc_qdiv'] argc:0
REG_EH_REGION 0x2
77: NOTE_INSN_BASIC_BLOCK 3
19: NOTE_INSN_DELETED
20: NOTE_INSN_DELETED
110: [%31:SI+0x20]=%1:DF
REG_EH_REGION 0x2
116: NOTE_INSN_BASIC_BLOCK 4
111: [%31:SI+0x28]=%2:DF
REG_EH_REGION 0x2
22: NOTE_INSN_BASIC_BLOCK 5
108: %0:DF=[%31:SI+0x20]
REG_EH_REGION 0x2
117: NOTE_INSN_BASIC_BLOCK 6
109: %1:DF=[%31:SI+0x28]
REG_EH_REGION 0x2
79: NOTE_INSN_BASIC_BLOCK 7
26: [%31:SI+0x18]=%0:DF
104: pc=L69
105: barrier
*after*
18: %1:TF=call [`__gcc_qdiv'] argc:0
REG_EH_REGION 0x2
77: NOTE_INSN_BASIC_BLOCK 3
19: NOTE_INSN_DELETED
20: NOTE_INSN_DELETED
110: [%31:SI+0x20]=%1:DF
111: [%31:SI+0x28]=%2:DF
108: %0:DF=[%31:SI+0x20]
109: %1:DF=[%31:SI+0x28]
26: [%31:SI+0x18]=%0:DF
104: pc=L69
105: barrier
PR rtl-optimization/90259
gcc/ChangeLog:
* function.cc (rest_of_handle_thread_prologue_and_epilogue): Add
parameter fun, and call function purge_all_dead_edges.
(pass_thread_prologue_and_epilogue::execute): Name unamed parameter
as fun, and use it for rest_of_handle_thread_prologue_and_epilogue.
gcc/testsuite/ChangeLog:
* g++.target/powerpc/pr90259.C: New.
2 files changed
