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[AArch64][GlobalISel] Use the look-through constant helper for the shift s32->s64 custom legalization. 

Almost NFC, except it catches more cases and gives a 0.1% CTMark -O0 size win.
This commit is contained in:
Amara Emerson 2020-09-27 01:22:55 -07:00
parent 82420b4e49
commit 7156938be2
2 changed files with 7 additions and 8 deletions
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10
llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
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@ -756,16 +756,14 @@ bool AArch64LegalizerInfo::legalizeShlAshrLshr(
// If the shift amount is a G_CONSTANT, promote it to a 64 bit type so the
// imported patterns can select it later. Either way, it will be legal.
Register AmtReg = MI.getOperand(2).getReg();
auto *CstMI = MRI.getVRegDef(AmtReg);
assert(CstMI && "expected to find a vreg def");
if (CstMI->getOpcode() != TargetOpcode::G_CONSTANT)
auto VRegAndVal = getConstantVRegValWithLookThrough(AmtReg, MRI);
if (!VRegAndVal)
return true;
// Check the shift amount is in range for an immediate form.
unsigned Amount = CstMI->getOperand(1).getCImm()->getZExtValue();
int64_t Amount = VRegAndVal->Value;
if (Amount > 31)
return true; // This will have to remain a register variant.
assert(MRI.getType(AmtReg).getSizeInBits() == 32);
auto ExtCst = MIRBuilder.buildZExt(LLT::scalar(64), AmtReg);
auto ExtCst = MIRBuilder.buildConstant(LLT::scalar(64), Amount);
MI.getOperand(2).setReg(ExtCst.getReg(0));
return true;
}

5
llvm/test/CodeGen/AArch64/GlobalISel/legalize-unmerge-values.mir
View File

@ -24,9 +24,10 @@ body: |
; CHECK-LABEL: name: test_unmerge_s4
; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $w0
; CHECK: [[UV:%[0-9]+]]:_(s8), [[UV1:%[0-9]+]]:_(s8), [[UV2:%[0-9]+]]:_(s8), [[UV3:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[COPY]](s32)
; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 4
; CHECK: [[C:%[0-9]+]]:_(s8) = G_CONSTANT i8 4
; CHECK: [[ZEXT:%[0-9]+]]:_(s32) = G_ZEXT [[UV]](s8)
; CHECK: [[LSHR:%[0-9]+]]:_(s32) = G_LSHR [[ZEXT]], [[C]](s32)
; CHECK: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 4
; CHECK: [[LSHR:%[0-9]+]]:_(s32) = G_LSHR [[ZEXT]], [[C1]](s64)
; CHECK: [[ANYEXT:%[0-9]+]]:_(s64) = G_ANYEXT [[UV]](s8)
; CHECK: [[ANYEXT1:%[0-9]+]]:_(s64) = G_ANYEXT [[LSHR]](s32)
; CHECK: $x0 = COPY [[ANYEXT]](s64)