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[LLVM][AArch64ExpandPseudo] Preserve undef flags when expanding SVE 1/2/3-op pseudo instructions. #149104

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Merged
merged 1 commit into from
Jul 17, 2025
Merged

[LLVM][AArch64ExpandPseudo] Preserve undef flags when expanding SVE 1/2/3-op pseudo instructions. #149104

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18 changes: 12 additions & 6 deletions llvm/lib/Target/AArch64/AArch64ExpandPseudoInsts.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -598,6 +598,9 @@ bool AArch64ExpandPseudo::expand_DestructiveOp(
llvm_unreachable("Unsupported ElementSize");
}

// Preserve undef state until DOP's reg is defined.
unsigned DOPRegState = MI.getOperand(DOPIdx).isUndef() ? RegState::Undef : 0;

//
// Create the destructive operation (if required)
//
Expand All @@ -616,10 +619,11 @@ bool AArch64ExpandPseudo::expand_DestructiveOp(
PRFX = BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(MovPrfxZero))
.addReg(DstReg, RegState::Define)
.addReg(MI.getOperand(PredIdx).getReg())
.addReg(MI.getOperand(DOPIdx).getReg());
.addReg(MI.getOperand(DOPIdx).getReg(), DOPRegState);

// After the movprfx, the destructive operand is same as Dst
DOPIdx = 0;
DOPRegState = 0;

// Create the additional LSL to zero the lanes when the DstReg is not
// unique. Zeros the lanes in z0 that aren't active in p0 with sequence
Expand All @@ -638,19 +642,21 @@ bool AArch64ExpandPseudo::expand_DestructiveOp(
assert(DOPRegIsUnique && "The destructive operand should be unique");
PRFX = BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(MovPrfx))
.addReg(DstReg, RegState::Define)
.addReg(MI.getOperand(DOPIdx).getReg());
.addReg(MI.getOperand(DOPIdx).getReg(), DOPRegState);
DOPIdx = 0;
DOPRegState = 0;
}

//
// Create the destructive operation
//
DOP = BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(Opcode))
.addReg(DstReg, RegState::Define | getDeadRegState(DstIsDead));
DOPRegState = DOPRegState | RegState::Kill;

switch (DType) {
case AArch64::DestructiveUnaryPassthru:
DOP.addReg(MI.getOperand(DOPIdx).getReg(), RegState::Kill)
DOP.addReg(MI.getOperand(DOPIdx).getReg(), DOPRegState)
.add(MI.getOperand(PredIdx))
.add(MI.getOperand(SrcIdx));
break;
Expand All @@ -659,12 +665,12 @@ bool AArch64ExpandPseudo::expand_DestructiveOp(
case AArch64::DestructiveBinaryComm:
case AArch64::DestructiveBinaryCommWithRev:
DOP.add(MI.getOperand(PredIdx))
.addReg(MI.getOperand(DOPIdx).getReg(), RegState::Kill)
.add(MI.getOperand(SrcIdx));
.addReg(MI.getOperand(DOPIdx).getReg(), DOPRegState)
.add(MI.getOperand(SrcIdx));
break;
case AArch64::DestructiveTernaryCommWithRev:
DOP.add(MI.getOperand(PredIdx))
.addReg(MI.getOperand(DOPIdx).getReg(), RegState::Kill)
.addReg(MI.getOperand(DOPIdx).getReg(), DOPRegState)
.add(MI.getOperand(SrcIdx))
.add(MI.getOperand(Src2Idx));
break;
Expand Down
81 changes: 81 additions & 0 deletions llvm/test/CodeGen/AArch64/sve-pseudos-expand-undef.mir
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Expand Up @@ -54,3 +54,84 @@ body: |
renamable $z0 = FADD_ZPZZ_D_UNDEF killed $p0, killed $z1, killed $z2, implicit-def $z0_z1_z2_z3
RET_ReallyLR implicit $z0_z1_z2_z3
...

---
name: unary_undef_operand
body: |
bb.0:
liveins: $p0, $z0

; CHECK: name: unary_undef_operand
; CHECK: $z0 = MOVPRFX_ZZ undef $z1
; CHECK: $z0 = ABS_ZPmZ_S internal killed $z0, renamable $p0, killed undef renamable $z1
; NOTE: Unary _UNDEF psuedo instructions ignore the passthru operand.
renamable $z0 = ABS_ZPmZ_S_UNDEF renamable $z0, renamable $p0, killed undef renamable $z1
RET_ReallyLR

...

---
name: binop_undef_operand
body: |
bb.0:
liveins: $p0, $z1

; CHECK: name: binop_undef_operand
; CHECK-NOT: MOVPRFX
; CHECK: $z0 = SMIN_ZPmZ_S renamable $p0, killed undef $z0, killed renamable $z1
renamable $z0 = SMIN_ZPZZ_S_UNDEF renamable $p0, undef renamable $z0, killed renamable $z1
RET_ReallyLR

...

---
name: binop_undef_operand_requires_movpfrx
body: |
bb.0:
liveins: $p0, $z1

; CHECK: name: binop_undef_operand_requires_movpfrx
; CHECK: $z0 = MOVPRFX_ZZ undef $z2
; CHECK: $z0 = SMIN_ZPmZ_S renamable $p0, internal killed $z0, killed renamable $z1
renamable $z0 = SMIN_ZPZZ_S_UNDEF renamable $p0, undef renamable $z2, killed renamable $z1
RET_ReallyLR

...

---
name: binop_undef_operand_requires_zeroing_movpfrx
body: |
bb.0:
liveins: $p0, $z1

; CHECK: name: binop_undef_operand_requires_zeroing_movpfrx
; CHECK: $z0 = MOVPRFX_ZPzZ_S $p0, undef $z2
; CHECK: $z0 = ADD_ZPmZ_S renamable $p0, internal killed $z0, killed renamable $z1
renamable $z0 = ADD_ZPZZ_S_ZERO renamable $p0, undef renamable $z2, killed renamable $z1
RET_ReallyLR

...

---
name: ternaryop_undef_operand
body: |
bb.0:
liveins: $p0, $z1, $z2
; CHECK: name: ternaryop_undef_operand
; CHECK-NOT: MOVPRFX
; CHECK: $z0 = MLA_ZPmZZ_B killed renamable $p0, killed undef $z0, killed renamable $z1, killed renamable $z2
renamable $z0 = MLA_ZPZZZ_B_UNDEF killed renamable $p0, killed undef renamable $z0, killed renamable $z1, killed renamable $z2
RET_ReallyLR implicit $z0
...

---
name: ternaryop_undef_operand_requires_movprfx
body: |
bb.0:
liveins: $p0, $z1, $z2
; CHECK: name: ternaryop_undef_operand_requires_movprfx
; CHECK: $z0 = MOVPRFX_ZZ undef $z3
; CHECK: $z0 = MLA_ZPmZZ_B killed renamable $p0, internal killed $z0, killed renamable $z1, killed renamable $z2
renamable $z0 = MLA_ZPZZZ_B_UNDEF killed renamable $p0, killed undef renamable $z3, killed renamable $z1, killed renamable $z2
RET_ReallyLR implicit $z0
...
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