[llvm] [InstCombine] Fold `getelementptr inbounds null, idx -> null` (PR #130742)

[Yingwei Zheng via llvm-commits]

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@@ -2910,6 +2910,13 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
                           SQ.getWithInstruction(&GEP)))
     return replaceInstUsesWith(GEP, V);
 
+  // getelementptr inbounds null, idx -> null
+  if (auto *BaseC = dyn_cast<Constant>(PtrOp))
+    if (GEP.isInBounds() && BaseC->isNullValue() &&
+        !NullPointerIsDefined(GEP.getFunction(),
+                              GEPType->getPointerAddressSpace()))
+      return replaceInstUsesWith(GEP, Constant::getNullValue(GEPType));
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dtcxzyw wrote:

Is it allowed to get the parent function from SQ.CxtI?


https://github.com/llvm/llvm-project/pull/130742