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* x86: Improved TrySwapMovCmp to insert before

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the FLAGS register is allocated.
This commit is contained in:
J. Gareth "Curious Kit" Moreton 2022-04-24 04:27:55 +01:00 committed by FPK
parent 6f24c8b4ef
commit 1fd2d3a83d
1 changed files with 9 additions and 4 deletions
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13
compiler/x86/aoptx86.pas
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@ -7920,11 +7920,16 @@ unit aoptx86;
{ The instruction can be safely moved }
asml.Remove(hp1);
{ Try to insert after the last instructions where the FLAGS register is not yet in use }
if not GetLastInstruction(p, hp2) then
asml.InsertBefore(hp1, p)
{ Try to insert before the FLAGS register is allocated, so "mov $0,%reg"
can be optimised into "xor %reg,%reg" later }
if SetAndTest(FindRegAllocBackward(NR_DEFAULTFLAGS, tai(p.Previous)), hp2) then
asml.InsertBefore(hp1, hp2)
else
asml.InsertAfter(hp1, hp2);
{ Note, if p.Previous is nil (even if it should logically never be the
case), FindRegAllocBackward immediately exits with False and so we
safely land here (we can't just pass p because FindRegAllocBackward
immediately exits on an instruction). [Kit] }
asml.InsertBefore(hp1, p);
DebugMsg(SPeepholeOptimization + 'Swapped ' + debug_op2str(taicpu(p).opcode) + ' and ' + debug_op2str(taicpu(hp1).opcode) + ' instructions to improve optimisation potential', hp1);