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

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-selectiondag

Author: Jim Lin (tclin914)

<details>
<summary>Changes</summary>

To get more better codegen for AArch with bic, x86 with andn and riscv with andn.

---
Full diff: https://github.com/llvm/llvm-project/pull/126667.diff


4 Files Affected:

- (modified) llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (+1-1) 
- (modified) llvm/test/CodeGen/AArch64/align-down.ll (+3-4) 
- (modified) llvm/test/CodeGen/X86/align-down.ll (+33-18) 
- (modified) llvm/test/CodeGen/X86/not-of-dec.ll (+7-8) 


``````````diff
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index f4caaf426de6a07..6c663d19675b842 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -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);
   }
diff --git a/llvm/test/CodeGen/AArch64/align-down.ll b/llvm/test/CodeGen/AArch64/align-down.ll
index 4b1cdfd2770f676..96e2a5d7d33f781 100644
--- a/llvm/test/CodeGen/AArch64/align-down.ll
+++ b/llvm/test/CodeGen/AArch64/align-down.ll
@@ -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
diff --git a/llvm/test/CodeGen/X86/align-down.ll b/llvm/test/CodeGen/X86/align-down.ll
index 3c64e108e06ddb0..c359c04f527a31f 100644
--- a/llvm/test/CodeGen/X86/align-down.ll
+++ b/llvm/test/CodeGen/X86/align-down.ll
@@ -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
diff --git a/llvm/test/CodeGen/X86/not-of-dec.ll b/llvm/test/CodeGen/X86/not-of-dec.ll
index 97906495031234f..29461619ac80557 100644
--- a/llvm/test/CodeGen/X86/not-of-dec.ll
+++ b/llvm/test/CodeGen/X86/not-of-dec.ll
@@ -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

``````````

</details>


https://github.com/llvm/llvm-project/pull/126667