[llvm] 8072222 - [InstCombine] Preserve all gep flags in gep of select fold

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2024-06-19T12:31:53+02:00
New Revision: 807222245e437aa693d0c8f8210cfe79a02cddb1

URL: https://github.com/llvm/llvm-project/commit/807222245e437aa693d0c8f8210cfe79a02cddb1
DIFF: https://github.com/llvm/llvm-project/commit/807222245e437aa693d0c8f8210cfe79a02cddb1.diff

LOG: [InstCombine] Preserve all gep flags in gep of select fold

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
    llvm/test/Transforms/InstCombine/getelementptr.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index f9c1b72e5ef73..d1b1ec8215a33 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2332,10 +2332,10 @@ static Instruction *foldSelectGEP(GetElementPtrInst &GEP,
   // Propagate 'inbounds' and metadata from existing instructions.
   // Note: using IRBuilder to create the constants for efficiency.
   SmallVector<Value *, 4> IndexC(GEP.indices());
-  bool IsInBounds = GEP.isInBounds();
+  GEPNoWrapFlags NW = GEP.getNoWrapFlags();
   Type *Ty = GEP.getSourceElementType();
-  Value *NewTrueC = Builder.CreateGEP(Ty, TrueC, IndexC, "", IsInBounds);
-  Value *NewFalseC = Builder.CreateGEP(Ty, FalseC, IndexC, "", IsInBounds);
+  Value *NewTrueC = Builder.CreateGEP(Ty, TrueC, IndexC, "", NW);
+  Value *NewFalseC = Builder.CreateGEP(Ty, FalseC, IndexC, "", NW);
   return SelectInst::Create(Cond, NewTrueC, NewFalseC, "", nullptr, Sel);
 }
 

diff  --git a/llvm/test/Transforms/InstCombine/getelementptr.ll b/llvm/test/Transforms/InstCombine/getelementptr.ll
index f968fa6f9afd0..a842484c25a86 100644
--- a/llvm/test/Transforms/InstCombine/getelementptr.ll
+++ b/llvm/test/Transforms/InstCombine/getelementptr.ll
@@ -1760,4 +1760,24 @@ define ptr @gep_to_i8_nusw_nuw(ptr %p) {
   ret ptr %gep
 }
 
+define ptr @gep_sel_const(i1 %c) {
+; CHECK-LABEL: @gep_sel_const(
+; CHECK-NEXT:    [[GEP:%.*]] = select i1 [[C:%.*]], ptr getelementptr (i8, ptr @A, i64 5), ptr getelementptr (i8, ptr @B, i64 5)
+; CHECK-NEXT:    ret ptr [[GEP]]
+;
+  %sel = select i1 %c, ptr @A, ptr @B
+  %gep = getelementptr i8, ptr %sel, i64 5
+  ret ptr %gep
+}
+
+define ptr @gep_sel_const_nuw(i1 %c) {
+; CHECK-LABEL: @gep_sel_const_nuw(
+; CHECK-NEXT:    [[GEP:%.*]] = select i1 [[C:%.*]], ptr getelementptr nuw (i8, ptr @A, i64 5), ptr getelementptr nuw (i8, ptr @B, i64 5)
+; CHECK-NEXT:    ret ptr [[GEP]]
+;
+  %sel = select i1 %c, ptr @A, ptr @B
+  %gep = getelementptr nuw i8, ptr %sel, i64 5
+  ret ptr %gep
+}
+
 !0 = !{!"branch_weights", i32 2, i32 10}