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backend/x64: Reduce conversions required for cpsr_nzcv

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The guest program often accesses the NZCV flags directly much less
often than we need to use them for jumps and other such uses.

Therefore, we store our flags in cpsr_nzcv in a x64-friendly format.

This allows for a reduction in conditional jump related code.
This commit is contained in:
MerryMage
2020-05-06 22:08:38 +01:00
parent f4922a97f6
commit 8b3bc92bce
7 changed files with 213 additions and 189 deletions
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27
src/backend/x64/emit_x64_data_processing.cpp
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@@ -126,56 +126,71 @@ static void EmitConditionalSelect(BlockOfCode& code, EmitContext& ctx, IR::Inst*
const Xbyak::Reg else_ = ctx.reg_alloc.UseScratchGpr(args[2]).changeBit(bitsize);
code.mov(nzcv, dword[r15 + code.GetJitStateInfo().offsetof_cpsr_nzcv]);
// TODO: Flag optimization
code.shr(nzcv, 28);
code.imul(nzcv, nzcv, 0b00010000'10000001);
code.and_(nzcv.cvt8(), 1);
code.add(nzcv.cvt8(), 0x7F); // restore OF
code.sahf(); // restore SF, ZF, CF
// sahf restores SF, ZF, CF
// add al, 0x7F restores OF
switch (args[0].GetImmediateCond()) {
case IR::Cond::EQ: //z
code.sahf();
code.cmovz(else_, then_);
break;
case IR::Cond::NE: //!z
code.sahf();
code.cmovnz(else_, then_);
break;
case IR::Cond::CS: //c
code.sahf();
code.cmovc(else_, then_);
break;
case IR::Cond::CC: //!c
code.sahf();
code.cmovnc(else_, then_);
break;
case IR::Cond::MI: //n
code.sahf();
code.cmovs(else_, then_);
break;
case IR::Cond::PL: //!n
code.sahf();
code.cmovns(else_, then_);
break;
case IR::Cond::VS: //v
code.add(nzcv.cvt8(), 0x7F);
code.cmovo(else_, then_);
break;
case IR::Cond::VC: //!v
code.add(nzcv.cvt8(), 0x7F);
code.cmovno(else_, then_);
break;
case IR::Cond::HI: //c & !z
code.sahf();
code.cmc();
code.cmova(else_, then_);
break;
case IR::Cond::LS: //!c | z
code.sahf();
code.cmc();
code.cmovna(else_, then_);
break;
case IR::Cond::GE: // n == v
code.add(nzcv.cvt8(), 0x7F);
code.sahf();
code.cmovge(else_, then_);
break;
case IR::Cond::LT: // n != v
code.add(nzcv.cvt8(), 0x7F);
code.sahf();
code.cmovl(else_, then_);
break;
case IR::Cond::GT: // !z & (n == v)
code.add(nzcv.cvt8(), 0x7F);
code.sahf();
code.cmovg(else_, then_);
break;
case IR::Cond::LE: // z | (n != v)
code.add(nzcv.cvt8(), 0x7F);
code.sahf();
code.cmovle(else_, then_);
break;
case IR::Cond::AL: