[llvm] 63babf5 - [InstCombine] Fix worklist management in transformToIndexedCompare()

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2023-06-01T10:35:13+02:00
New Revision: 63babf54c22ab2045082b03d6794fac0738cad25

URL: https://github.com/llvm/llvm-project/commit/63babf54c22ab2045082b03d6794fac0738cad25
DIFF: https://github.com/llvm/llvm-project/commit/63babf54c22ab2045082b03d6794fac0738cad25.diff

LOG: [InstCombine] Fix worklist management in transformToIndexedCompare()

Use replaceInstUsesWith() rather than plain RAUW to make sure the
old instructions are added back to the worklist for DCE.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 462e65d8e7d6..d0bff3a6a540 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -534,7 +534,8 @@ static void setInsertionPoint(IRBuilder<> &Builder, Value *V,
 /// pointer.
 static Value *rewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base,
                                  const DataLayout &DL,
-                                 SetVector<Value *> &Explored) {
+                                 SetVector<Value *> &Explored,
+                                 InstCombiner &IC) {
   // Perform all the substitutions. This is a bit tricky because we can
   // have cycles in our use-def chains.
   // 1. Create the PHI nodes without any incoming values.
@@ -636,7 +637,7 @@ static Value *rewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base,
                                        Val->getName() + ".ptr");
     NewVal = Builder.CreateBitOrPointerCast(
         NewVal, Val->getType(), Val->getName() + ".conv");
-    Val->replaceAllUsesWith(NewVal);
+    IC.replaceInstUsesWith(*cast<Instruction>(Val), NewVal);
   }
 
   return NewInsts[Start];
@@ -689,7 +690,8 @@ getAsConstantIndexedAddress(Type *ElemTy, Value *V, const DataLayout &DL) {
 /// between GEPLHS and RHS.
 static Instruction *transformToIndexedCompare(GEPOperator *GEPLHS, Value *RHS,
                                               ICmpInst::Predicate Cond,
-                                              const DataLayout &DL) {
+                                              const DataLayout &DL,
+                                              InstCombiner &IC) {
   // FIXME: Support vector of pointers.
   if (GEPLHS->getType()->isVectorTy())
     return nullptr;
@@ -713,7 +715,7 @@ static Instruction *transformToIndexedCompare(GEPOperator *GEPLHS, Value *RHS,
   // can't have overflow on either side. We can therefore re-write
   // this as:
   //   OFFSET1 cmp OFFSET2
-  Value *NewRHS = rewriteGEPAsOffset(ElemTy, RHS, PtrBase, DL, Nodes);
+  Value *NewRHS = rewriteGEPAsOffset(ElemTy, RHS, PtrBase, DL, Nodes, IC);
 
   // RewriteGEPAsOffset has replaced RHS and all of its uses with a re-written
   // GEP having PtrBase as the pointer base, and has returned in NewRHS the
@@ -832,7 +834,7 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
       // Otherwise, the base pointers are 
diff erent and the indices are
       // 
diff erent. Try convert this to an indexed compare by looking through
       // PHIs/casts.
-      return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
+      return transformToIndexedCompare(GEPLHS, RHS, Cond, DL, *this);
     }
 
     // If one of the GEPs has all zero indices, recurse.
@@ -896,7 +898,7 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
 
   // Try convert this to an indexed compare by looking through PHIs/casts as a
   // last resort.
-  return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
+  return transformToIndexedCompare(GEPLHS, RHS, Cond, DL, *this);
 }
 
 bool InstCombinerImpl::foldAllocaCmp(AllocaInst *Alloca) {