[llvm] 1b1c817 - [InstCombine] Drop poison flags in simplifyAssocCastAssoc()

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2023-11-09T11:58:02+01:00
New Revision: 1b1c81772fe50a1cb2b2adf8d8cf442c0b73602f

URL: https://github.com/llvm/llvm-project/commit/1b1c81772fe50a1cb2b2adf8d8cf442c0b73602f
DIFF: https://github.com/llvm/llvm-project/commit/1b1c81772fe50a1cb2b2adf8d8cf442c0b73602f.diff

LOG: [InstCombine] Drop poison flags in simplifyAssocCastAssoc()

The nneg flag on zext may no longer hold after the reassociation.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
    llvm/test/Transforms/InstCombine/assoc-cast-assoc.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 1474cc9c3fdb54e..2e0b185769041cc 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -356,6 +356,7 @@ static bool simplifyAssocCastAssoc(BinaryOperator *BinOp1,
 
   IC.replaceOperand(*Cast, 0, BinOp2->getOperand(0));
   IC.replaceOperand(*BinOp1, 1, FoldedC);
+  Cast->dropPoisonGeneratingFlags();
   return true;
 }
 

diff  --git a/llvm/test/Transforms/InstCombine/assoc-cast-assoc.ll b/llvm/test/Transforms/InstCombine/assoc-cast-assoc.ll
index 61039f7f1a5d9e6..2d15318d0b0a4b6 100644
--- a/llvm/test/Transforms/InstCombine/assoc-cast-assoc.ll
+++ b/llvm/test/Transforms/InstCombine/assoc-cast-assoc.ll
@@ -77,8 +77,9 @@ define <2 x i32> @AndZextAndVec(<2 x i8> %a) {
 
 define i24 @zext_nneg(i16 %a) {
 ; CHECK-LABEL: @zext_nneg(
-; CHECK-NEXT:    [[RESIZE:%.*]] = zext nneg i16 [[A:%.*]] to i24
-; CHECK-NEXT:    ret i24 [[RESIZE]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i16 [[A:%.*]], 32767
+; CHECK-NEXT:    [[AND2:%.*]] = zext nneg i16 [[TMP1]] to i24
+; CHECK-NEXT:    ret i24 [[AND2]]
 ;
   %and1 = and i16 %a, 32767
   %resize = zext nneg i16 %and1 to i24