[llvm] 547dc46 - [DAG] SimplifyDemandedBits - ensure we drop NSW/NUW flags when we simplify a SHL node's input
Simon Pilgrim via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 26 02:35:09 PDT 2023
Author: Simon Pilgrim
Date: 2023-10-26T10:34:58+01:00
New Revision: 547dc461225ba65b6d5dac34efd31d2c8c5b1049
URL: https://github.com/llvm/llvm-project/commit/547dc461225ba65b6d5dac34efd31d2c8c5b1049
DIFF: https://github.com/llvm/llvm-project/commit/547dc461225ba65b6d5dac34efd31d2c8c5b1049.diff
LOG: [DAG] SimplifyDemandedBits - ensure we drop NSW/NUW flags when we simplify a SHL node's input
We already do this for variable shifts, but we missed it for constant shifts
Fixes #69965
Added:
Modified:
llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
llvm/test/CodeGen/X86/pr69965.ll
Removed:
################################################################################
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 8b4f3159499122a..c139850eb996354 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1786,8 +1786,17 @@ bool TargetLowering::SimplifyDemandedBits(
APInt InDemandedMask = DemandedBits.lshr(ShAmt);
if (SimplifyDemandedBits(Op0, InDemandedMask, DemandedElts, Known, TLO,
- Depth + 1))
+ Depth + 1)) {
+ SDNodeFlags Flags = Op.getNode()->getFlags();
+ if (Flags.hasNoSignedWrap() || Flags.hasNoUnsignedWrap()) {
+ // Disable the nsw and nuw flags. We can no longer guarantee that we
+ // won't wrap after simplification.
+ Flags.setNoSignedWrap(false);
+ Flags.setNoUnsignedWrap(false);
+ Op->setFlags(Flags);
+ }
return true;
+ }
assert(!Known.hasConflict() && "Bits known to be one AND zero?");
Known.Zero <<= ShAmt;
Known.One <<= ShAmt;
diff --git a/llvm/test/CodeGen/X86/pr69965.ll b/llvm/test/CodeGen/X86/pr69965.ll
index 47bec4d7b1ab563..33bea976c7896d8 100644
--- a/llvm/test/CodeGen/X86/pr69965.ll
+++ b/llvm/test/CodeGen/X86/pr69965.ll
@@ -10,10 +10,12 @@ define i64 @PR69965(ptr %input_ptrs, ptr %output_ptrs) {
; X86-NEXT: movl (%eax), %eax
; X86-NEXT: movzbl (%eax), %eax
; X86-NEXT: notl %eax
-; X86-NEXT: movzbl %al, %edx
-; X86-NEXT: shll $8, %eax
+; X86-NEXT: movl %eax, %edx
+; X86-NEXT: shll $8, %edx
; X86-NEXT: movl (%ecx), %ecx
-; X86-NEXT: leal (%eax,%edx,2), %eax
+; X86-NEXT: addb %al, %al
+; X86-NEXT: movzbl %al, %eax
+; X86-NEXT: orl %edx, %eax
; X86-NEXT: orl $32768, %eax # imm = 0x8000
; X86-NEXT: movw %ax, (%ecx)
; X86-NEXT: xorl %eax, %eax
@@ -25,13 +27,14 @@ define i64 @PR69965(ptr %input_ptrs, ptr %output_ptrs) {
; X64-NEXT: movq (%rdi), %rax
; X64-NEXT: movzbl (%rax), %eax
; X64-NEXT: notl %eax
-; X64-NEXT: movzbl %al, %ecx
-; X64-NEXT: # kill: def $eax killed $eax def $rax
+; X64-NEXT: leal (%rax,%rax), %ecx
+; X64-NEXT: # kill: def $eax killed $eax killed $rax
; X64-NEXT: shll $8, %eax
; X64-NEXT: movq (%rsi), %rdx
-; X64-NEXT: leal (%rax,%rcx,2), %eax
-; X64-NEXT: orl $32768, %eax # imm = 0x8000
-; X64-NEXT: movw %ax, (%rdx)
+; X64-NEXT: movzbl %cl, %ecx
+; X64-NEXT: orl %eax, %ecx
+; X64-NEXT: orl $32768, %ecx # imm = 0x8000
+; X64-NEXT: movw %cx, (%rdx)
; X64-NEXT: xorl %eax, %eax
; X64-NEXT: retq
entry:
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