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* avoid unneeded the generation of un-needed shift instructions thlcgobj.in a_load_subsetreg_reg

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git-svn-id: trunk@37374 -
This commit is contained in:
florian 2017-10-01 16:13:22 +00:00
parent 6f338bb4b5
commit 75e03a7e62
1 changed files with 23 additions and 16 deletions

39
compiler/hlcgobj.pas
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@ -1281,25 +1281,32 @@ implementation
begin
subsetregdef:=cgsize_orddef(sreg.subsetregsize);
tmpreg:=getintregister(list,subsetregdef);
if is_signed(subsetsize) then
{ insert shifts only if it changes bits being accessed later on }
if (sreg.startbit<>0) or
(tosize.size*8>sreg.bitlen) then
begin
{ sign extend in case the value has a bitsize mod 8 <> 0 }
{ both instructions will be optimized away if not }
a_op_const_reg_reg(list,OP_SHL,subsetregdef,(tcgsize2size[sreg.subsetregsize]*8)-sreg.startbit-sreg.bitlen,sreg.subsetreg,tmpreg);
a_op_const_reg(list,OP_SAR,subsetregdef,(tcgsize2size[sreg.subsetregsize]*8)-sreg.bitlen,tmpreg);
if is_signed(subsetsize) then
begin
{ sign extend in case the value has a bitsize mod 8 <> 0 }
{ both instructions will be optimized away if not }
a_op_const_reg_reg(list,OP_SHL,subsetregdef,(tcgsize2size[sreg.subsetregsize]*8)-sreg.startbit-sreg.bitlen,sreg.subsetreg,tmpreg);
a_op_const_reg(list,OP_SAR,subsetregdef,(tcgsize2size[sreg.subsetregsize]*8)-sreg.bitlen,tmpreg);
end
else
begin
a_op_const_reg_reg(list,OP_SHR,subsetregdef,sreg.startbit,sreg.subsetreg,tmpreg);
stopbit:=sreg.startbit+sreg.bitlen;
// on x86(64), 1 shl 32(64) = 1 instead of 0
// use aword to prevent overflow with 1 shl 31
if (stopbit-sreg.startbit<>AIntBits) then
bitmask:=(aword(1) shl (stopbit-sreg.startbit))-1
else
bitmask:=high(aword);
a_op_const_reg(list,OP_AND,subsetregdef,tcgint(bitmask),tmpreg);
end;
end
else
begin
a_op_const_reg_reg(list,OP_SHR,subsetregdef,sreg.startbit,sreg.subsetreg,tmpreg);
stopbit:=sreg.startbit+sreg.bitlen;
// on x86(64), 1 shl 32(64) = 1 instead of 0
// use aword to prevent overflow with 1 shl 31
if (stopbit-sreg.startbit<>AIntBits) then
bitmask:=(aword(1) shl (stopbit-sreg.startbit))-1
else
bitmask:=high(aword);
a_op_const_reg(list,OP_AND,subsetregdef,tcgint(bitmask),tmpreg);
end;
a_load_reg_reg(list,subsetregdef,subsetregdef,sreg.subsetreg,tmpreg);
subsetsizereg:=getintregister(list,subsetsize);
a_load_reg_reg(list,subsetregdef,subsetsize,tmpreg,subsetsizereg);
a_load_reg_reg(list,subsetsize,tosize,subsetsizereg,destreg);