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[DAGCombiner] Add hasOneUse checks for folding (not (add X, -1)) to (neg X) #126667

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Merged
merged 2 commits into from
Feb 12, 2025
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[DAGCombiner] Add hasOneUse checks for folding (not (add X, -1)) to (neg X) #126667

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[DAGCombiner] Add hasOneUse checks for folding (not (add X, -1)) to (…
tclin914 Feb 11, 2025
c94af5d
Address arsenm's comment
tclin914 Feb 12, 2025
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2 changes: 1 addition & 1 deletion llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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Expand Up @@ -9702,7 +9702,7 @@ SDValue DAGCombiner::visitXOR(SDNode *N) {
}

// fold (not (add X, -1)) -> (neg X)
if (isAllOnesConstant(N1) && N0.getOpcode() == ISD::ADD &&
if (isAllOnesConstant(N1) && N0.getOpcode() == ISD::ADD && N0.hasOneUse() &&
isAllOnesOrAllOnesSplat(N0.getOperand(1))) {
return DAG.getNegative(N0.getOperand(0), DL, VT);
}
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7 changes: 3 additions & 4 deletions llvm/test/CodeGen/AArch64/align-down.ll
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Expand Up @@ -54,10 +54,9 @@ define i32 @t2_commutative(i32 %ptr, i32 %alignment) nounwind {
define i32 @t3_extrause0(i32 %ptr, i32 %alignment, ptr %mask_storage) nounwind {
; CHECK-LABEL: t3_extrause0:
; CHECK: // %bb.0:
; CHECK-NEXT: neg w8, w1
; CHECK-NEXT: sub w9, w1, #1
; CHECK-NEXT: and w0, w0, w8
; CHECK-NEXT: str w9, [x2]
; CHECK-NEXT: sub w8, w1, #1
; CHECK-NEXT: bic w0, w0, w8
; CHECK-NEXT: str w8, [x2]
; CHECK-NEXT: ret
%mask = add i32 %alignment, -1
store i32 %mask, ptr %mask_storage
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51 changes: 33 additions & 18 deletions llvm/test/CodeGen/X86/align-down.ll
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Expand Up @@ -82,25 +82,40 @@ define i32 @t2_commutative(i32 %ptr, i32 %alignment) nounwind {
; Extra use tests

define i32 @t3_extrause0(i32 %ptr, i32 %alignment, ptr %mask_storage) nounwind {
; X86-LABEL: t3_extrause0:
; X86: # %bb.0:
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: leal -1(%eax), %edx
; X86-NEXT: movl %edx, (%ecx)
; X86-NEXT: negl %eax
; X86-NEXT: andl {{[0-9]+}}(%esp), %eax
; X86-NEXT: retl
; NOBMI-X86-LABEL: t3_extrause0:
; NOBMI-X86: # %bb.0:
; NOBMI-X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; NOBMI-X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; NOBMI-X86-NEXT: decl %eax
; NOBMI-X86-NEXT: movl %eax, (%ecx)
; NOBMI-X86-NEXT: notl %eax
; NOBMI-X86-NEXT: andl {{[0-9]+}}(%esp), %eax
; NOBMI-X86-NEXT: retl
;
; X64-LABEL: t3_extrause0:
; X64: # %bb.0:
; X64-NEXT: movl %esi, %eax
; X64-NEXT: leal -1(%rax), %ecx
; X64-NEXT: movl %ecx, (%rdx)
; X64-NEXT: negl %eax
; X64-NEXT: andl %edi, %eax
; X64-NEXT: # kill: def $eax killed $eax killed $rax
; X64-NEXT: retq
; BMI-X86-LABEL: t3_extrause0:
; BMI-X86: # %bb.0:
; BMI-X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; BMI-X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; BMI-X86-NEXT: decl %ecx
; BMI-X86-NEXT: movl %ecx, (%eax)
; BMI-X86-NEXT: andnl {{[0-9]+}}(%esp), %ecx, %eax
; BMI-X86-NEXT: retl
;
; NOBMI-X64-LABEL: t3_extrause0:
; NOBMI-X64: # %bb.0:
; NOBMI-X64-NEXT: # kill: def $esi killed $esi def $rsi
; NOBMI-X64-NEXT: leal -1(%rsi), %eax
; NOBMI-X64-NEXT: movl %eax, (%rdx)
; NOBMI-X64-NEXT: notl %eax
; NOBMI-X64-NEXT: andl %edi, %eax
; NOBMI-X64-NEXT: retq
;
; BMI-X64-LABEL: t3_extrause0:
; BMI-X64: # %bb.0:
; BMI-X64-NEXT: decl %esi
; BMI-X64-NEXT: movl %esi, (%rdx)
; BMI-X64-NEXT: andnl %edi, %esi, %eax
; BMI-X64-NEXT: retq
%mask = add i32 %alignment, -1
store i32 %mask, ptr %mask_storage
%bias = and i32 %ptr, %mask
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15 changes: 7 additions & 8 deletions llvm/test/CodeGen/X86/not-of-dec.ll
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Expand Up @@ -57,18 +57,17 @@ define i32 @t2_extrause(i32 %alignment, ptr %mask_storage) nounwind {
; X86: # %bb.0:
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: leal -1(%eax), %edx
; X86-NEXT: movl %edx, (%ecx)
; X86-NEXT: negl %eax
; X86-NEXT: decl %eax
; X86-NEXT: movl %eax, (%ecx)
; X86-NEXT: notl %eax
; X86-NEXT: retl
;
; X64-LABEL: t2_extrause:
; X64: # %bb.0:
; X64-NEXT: movl %edi, %eax
; X64-NEXT: leal -1(%rax), %ecx
; X64-NEXT: movl %ecx, (%rsi)
; X64-NEXT: negl %eax
; X64-NEXT: # kill: def $eax killed $eax killed $rax
; X64-NEXT: # kill: def $edi killed $edi def $rdi
; X64-NEXT: leal -1(%rdi), %eax
; X64-NEXT: movl %eax, (%rsi)
; X64-NEXT: notl %eax
; X64-NEXT: retq
%mask = add i32 %alignment, -1
store i32 %mask, ptr %mask_storage
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