[llvm] [InstCombine] Remove one-use restriction on icmp of gep fold (PR #76730)

[Yingwei Zheng via llvm-commits]

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@@ -813,14 +813,28 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
       }
     }
 
-    // Only lower this if the icmp is the only user of the GEP or if we expect
-    // the result to fold to a constant!
-    if ((GEPsInBounds || CmpInst::isEquality(Cond)) &&
-        (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
-        (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse())) {
+    if (GEPsInBounds || CmpInst::isEquality(Cond)) {
+      auto EmitGEPOffsetAndRewrite = [&](GEPOperator *GEP) {
+        auto *Inst = dyn_cast<Instruction>(GEP);
+        if (Inst)
+          Builder.SetInsertPoint(Inst);
+
+        Value *Offset = EmitGEPOffset(GEP);
+        // If a non-trivial GEP has other uses, rewrite it to avoid duplicating
+        // the offset arithmetic.
+        if (Inst && !GEP->hasOneUse() && !GEP->hasAllConstantIndices()) {
+          replaceInstUsesWith(*Inst,
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dtcxzyw wrote:

Can we avoid creating a new GEP when the source type of GEP is already `i8`?


https://github.com/llvm/llvm-project/pull/76730