[CodeGenPrepare][RISCV] Remove asserting VH references before erasing the dead GEP

[dtcxzyw]

Summary

Fixes issue https://github.com/llvm/llvm-project/issues/63365

[craig.topper]

LGTM

llvm/lib/CodeGen/CodeGenPrepare.cpp

bool CodeGenPrepare::optimizeInst(Instruction *I, ModifyDT &ModifiedDT) {
 
   if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
     if (GEPI->hasAllZeroIndices()) {
       /// The GEP operand must be a pointer, so must its result -> BitCast
       Instruction *NC = new BitCastInst(GEPI->getOperand(0), GEPI->getType(),
                                         GEPI->getName(), GEPI);
       NC->setDebugLoc(GEPI->getDebugLoc());
       replaceAllUsesWith(GEPI, NC, FreshBBs, IsHugeFunc);
-      GEPI->eraseFromParent();
+      RecursivelyDeleteTriviallyDeadInstructions(
+          GEPI, TLInfo, nullptr,
+          [&](Value *V) { removeAllAssertingVHReferences(V); });
       ++NumGEPsElim;
       optimizeInst(NC, ModifiedDT);
       return true;
     }
     if (tryUnmergingGEPsAcrossIndirectBr(GEPI, TTI)) {
       return true;
     }
     return false;

llvm/test/CodeGen/RISCV/pr63365.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=riscv32 | FileCheck %s
+
+@G = external global i32
+@G.1 = external global i32
+@G.2 = external global i64
+@G.3 = external global i1
+@G.4 = external global i1
+@G.5 = external global i8
+
+define void @f() {
+; CHECK-LABEL: f:
+; CHECK:       # %bb.0: # %BB
+; CHECK-NEXT:    addi sp, sp, -16
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    addi sp, sp, 16
+; CHECK-NEXT:    ret
+BB:
+  %A1 = alloca ptr, align 8
+  %G4 = getelementptr i1, ptr %A1, i32 65536
+  %G = getelementptr i1, ptr %A1, i64 4294967296
+  %L2 = load i8, ptr %G4, align 1
+  store i8 poison, ptr %G, align 1
+  ret void
+}