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* x86: Additional STC/CLC; J(N)C deterministic jump optimisation

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J. Gareth "Curious Kit" Moreton 2024-01-28 14:32:26 +00:00 committed by FPK
parent 698d432cce
commit de03a1b894
1 changed files with 56 additions and 12 deletions
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68
compiler/x86/aoptx86.pas
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@ -9436,20 +9436,67 @@ unit aoptx86;
if (hp1.typ = ait_instruction) and
IsJumpToLabel(taicpu(hp1)) then
begin
JumpLabel := TAsmLabel(taicpu(hp1).oper[0]^.ref^.symbol);
if not Assigned(JumpLabel) then
InternalError(2024012801);
{ Optimise the J(c); stc/clc optimisation first since this will
get missed if the main optimisation takes place }
if (taicpu(hp1).opcode = A_JCC) and
GetNextInstruction(hp1, hp2) and
MatchInstruction(hp2, A_CLC, A_STC, []) and
TryJccStcClcOpt(hp1, hp2) then
if (taicpu(hp1).opcode = A_JCC) then
begin
Result := True;
Exit;
if GetNextInstruction(hp1, hp2) and
MatchInstruction(hp2, A_CLC, A_STC, []) and
TryJccStcClcOpt(hp1, hp2) then
begin
Result := True;
Exit;
end;
hp2 := nil; { Suppress compiler warning }
if (taicpu(hp1).condition in [C_C, C_NC]) and
{ Make sure the flags aren't used again }
SetAndTest(FindRegDealloc(NR_DEFAULTFLAGS, tai(hp1.Next)), hp2) then
begin
{ clc + jc = False; clc + jnc = True; stc + jc = True; stc + jnc = False }
if ((taicpu(p).opcode = A_STC) xor (taicpu(hp1).condition = C_NC)) then
begin
if (taicpu(p).opcode = A_STC) then
DebugMsg(SPeepholeOptimization + 'STC; JC -> JMP (Deterministic jump) (StcJc2Jmp)', p)
else
DebugMsg(SPeepholeOptimization + 'CLC; JNC -> JMP (Deterministic jump) (ClcJnc2Jmp)', p);
MakeUnconditional(taicpu(hp1));
{ Move the jump to after the flag deallocations }
Asml.Remove(hp1);
Asml.InsertAfter(hp1, hp2);
RemoveCurrentP(p, hp1);
RemoveDeadCodeAfterJump(p); { Might as well do it now }
end
else
begin
JumpLabel.DecRefs;
if (taicpu(p).opcode = A_STC) then
DebugMsg(SPeepholeOptimization + 'STC; JNC -> NOP (Deterministic jump) (StcJnc2Nop)', p)
else
DebugMsg(SPeepholeOptimization + 'CLC; JC -> NOP (Deterministic jump) (ClcJc2Nop)', p);
{ In this case, the jump is deterministic in that it will never be taken }
RemoveCurrentP(p, tai(hp1.Next)); { hp1 will get removed too }
RemoveInstruction(hp1);
end;
Result := True;
Exit;
end;
end;
hp2 := nil; { Suppress compiler warning }
JumpLabel := TAsmLabel(taicpu(hp1).oper[0]^.ref^.symbol);
if Assigned(JumpLabel) and
if
{ Make sure the carry flag doesn't appear in the jump conditions }
not (taicpu(hp1).condition in [C_AE, C_NB, C_NC, C_B, C_C, C_NAE, C_BE, C_NA]) and
SetAndTest(getlabelwithsym(JumpLabel), hp2) and
GetNextInstruction(hp2, p_dist) and
MatchInstruction(p_dist, A_Jcc, A_SETcc, []) and
@ -9486,9 +9533,8 @@ unit aoptx86;
if { Make sure the flags aren't used again }
SetAndTest(FindRegDealloc(NR_DEFAULTFLAGS, tai(p_dist.Next)), hp2) and
GetNextInstruction(hp2, hp1_dist) and
(Hp1_dist.typ = ait_instruction) and
IsJumpToLabel(taicpu(hp1_dist)) and
{ Make sure the carry flag doesn't appear in the jump conditions }
not (taicpu(hp1).condition in [C_AE, C_NB, C_NC, C_B, C_C, C_NAE, C_BE, C_NA]) and
not (taicpu(hp1_dist).condition in [C_AE, C_NB, C_NC, C_B, C_C, C_NAE, C_BE, C_NA]) and
{ This works if hp1_dist or both are regular JMP instructions }
condition_in(taicpu(hp1).condition, taicpu(hp1_dist).condition) then
@ -9570,8 +9616,6 @@ unit aoptx86;
{ Make sure the flags aren't used again }
Assigned(FindRegDealloc(NR_DEFAULTFLAGS, tai(hp3.Next))) then
begin
tai_label(hp2).labsym.DecRefs;
taicpu(hp1).allocate_oper(1);
taicpu(hp1).ops := 1;
taicpu(hp1).loadsymbol(0, TAsmLabel(taicpu(hp3).oper[0]^.ref^.symbol), 0);