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xor optimisation now doesn't check to see if the REX prefix will actually be removed, as it's beneficial for speed reasons to only use the 32-bit register when zeroing the whole thing

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J. Gareth "Curious Kit" Moreton 2021-10-10 09:15:43 +01:00 committed by FPK
parent 2c180cf101
commit a925522ead
1 changed files with 8 additions and 33 deletions
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41
compiler/x86/aoptx86.pas
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@ -10326,28 +10326,6 @@ unit aoptx86;
end;
end;
{$ifdef x86_64}
{ Code size reduction by J. Gareth "Kit" Moreton }
{ Convert MOVZBQ and MOVZWQ to MOVZBL and MOVZWL respectively if it removes the REX prefix }
if (taicpu(p).opsize in [S_BQ, S_WQ]) and
(getsupreg(taicpu(p).oper[1]^.reg) in [RS_RAX, RS_RCX, RS_RDX, RS_RBX, RS_RSI, RS_RDI, RS_RBP, RS_RSP])
then
begin
{ Has 64-bit register name and opcode suffix }
PreMessage := 'movz' + debug_opsize2str(taicpu(p).opsize) + ' ' + debug_operstr(taicpu(p).oper[0]^) + ',' + debug_regname(taicpu(p).oper[1]^.reg) + ' -> movz';
{ The actual optimization }
setsubreg(taicpu(p).oper[1]^.reg, R_SUBD);
if taicpu(p).opsize = S_BQ then
taicpu(p).changeopsize(S_BL)
else
taicpu(p).changeopsize(S_WL);
DebugMsg(SPeepholeOptimization + PreMessage +
debug_opsize2str(taicpu(p).opsize) + ' ' + debug_operstr(taicpu(p).oper[0]^) + ',' + debug_regname(taicpu(p).oper[1]^.reg) + ' (removes REX prefix)', p);
end;
{$endif}
end;
@ -10371,20 +10349,17 @@ unit aoptx86;
case taicpu(p).opsize of
S_Q:
begin
if (getsupreg(taicpu(p).oper[0]^.reg) in [RS_RAX, RS_RCX, RS_RDX, RS_RBX, RS_RSI, RS_RDI, RS_RBP, RS_RSP]) then
begin
RegName := debug_regname(taicpu(p).oper[0]^.reg); { 64-bit register name }
PreMessage := 'xorq ' + RegName + ',' + RegName + ' -> xorl ';
RegName := debug_regname(taicpu(p).oper[0]^.reg); { 64-bit register name }
PreMessage := 'xorq ' + RegName + ',' + RegName + ' -> xorl ';
{ The actual optimization }
setsubreg(taicpu(p).oper[0]^.reg, R_SUBD);
setsubreg(taicpu(p).oper[1]^.reg, R_SUBD);
taicpu(p).changeopsize(S_L);
{ The actual optimization }
setsubreg(taicpu(p).oper[0]^.reg, R_SUBD);
setsubreg(taicpu(p).oper[1]^.reg, R_SUBD);
taicpu(p).changeopsize(S_L);
RegName := debug_regname(taicpu(p).oper[0]^.reg); { 32-bit register name }
RegName := debug_regname(taicpu(p).oper[0]^.reg); { 32-bit register name }
DebugMsg(SPeepholeOptimization + PreMessage + RegName + ',' + RegName + ' (removes REX prefix)', p);
end;
DebugMsg(SPeepholeOptimization + PreMessage + RegName + ',' + RegName + ' (32-bit register recommended when zeroing 64-bit counterpart)', p);
end;
else
;