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IR: Add microinstructions UnsignedSaturation and SignedSaturation

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MerryMage 2016-12-21 14:16:48 +00:00 • committed by Merry
parent b1df70578f
commit 6a269a6ebd
4 changed files with 93 additions and 0 deletions
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75
src/backend_x64/emit_x64.cpp
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@ -1348,6 +1348,81 @@ void EmitX64::EmitSignedSaturatedSub(IR::Block& block, IR::Inst* inst) {
}
}
void EmitX64::EmitUnsignedSaturation(IR::Block& block, IR::Inst* inst) {
auto overflow_inst = inst->GetAssociatedPseudoOperation(IR::Opcode::GetOverflowFromOp);
IR::Value a = inst->GetArg(0);
size_t N = inst->GetArg(1).GetU8();
ASSERT(N <= 31);
u32 saturated_value = (1u << N) - 1;
Xbyak::Reg32 result = reg_alloc.DefGpr(inst).cvt32();
Xbyak::Reg32 reg_a = reg_alloc.UseGpr(a).cvt32();
Xbyak::Reg32 overflow = overflow_inst ? reg_alloc.DefGpr(overflow_inst).cvt32() : reg_alloc.ScratchGpr().cvt32();
// Pseudocode: result = clamp(reg_a, 0, saturated_value);
code->xor_(overflow, overflow);
code->cmp(reg_a, saturated_value);
code->mov(result, saturated_value);
code->cmovle(result, overflow);
code->cmovbe(result, reg_a);
if (overflow_inst) {
EraseInstruction(block, overflow_inst);
inst->DecrementRemainingUses();
code->seta(overflow.cvt8());
}
}
void EmitX64::EmitSignedSaturation(IR::Block& block, IR::Inst* inst) {
auto overflow_inst = inst->GetAssociatedPseudoOperation(IR::Opcode::GetOverflowFromOp);
IR::Value a = inst->GetArg(0);
size_t N = inst->GetArg(1).GetU8();
ASSERT(N >= 1 && N <= 32);
if (N == 32) {
reg_alloc.RegisterAddDef(inst, a);
if (overflow_inst) {
auto no_overflow = IR::Value(false);
overflow_inst->ReplaceUsesWith(no_overflow);
}
return;
}
u32 mask = (1u << N) - 1;
u32 positive_saturated_value = (1u << (N - 1)) - 1;
u32 negative_saturated_value = 1u << (N - 1);
u32 sext_negative_satured_value = Common::SignExtend(N, negative_saturated_value);
Xbyak::Reg32 result = reg_alloc.DefGpr(inst).cvt32();
Xbyak::Reg32 reg_a = reg_alloc.UseGpr(a).cvt32();
Xbyak::Reg32 overflow = overflow_inst ? reg_alloc.DefGpr(overflow_inst).cvt32() : reg_alloc.ScratchGpr().cvt32();
Xbyak::Reg32 tmp = reg_alloc.ScratchGpr().cvt32();
// overflow now contains a value between 0 and mask if it was originally between {negative,positive}_saturated_value.
code->lea(overflow, code->ptr[reg_a.cvt64() + negative_saturated_value]);
// Put the appropriate saturated value in result
code->cmp(reg_a, positive_saturated_value);
code->mov(tmp, positive_saturated_value);
code->mov(result, sext_negative_satured_value);
code->cmovg(result, tmp);
// Do the saturation
code->cmp(overflow, mask);
code->cmovbe(result, reg_a);
if (overflow_inst) {
EraseInstruction(block, overflow_inst);
inst->DecrementRemainingUses();
code->seta(overflow.cvt8());
}
}
/**
* Extracts the most significant bits from each of the packed bytes, and packs them together.
*