[DAGCombiner] Fix crash when trying to replace an indexed store with a narrow store.

[aemerson]

Summary

rdar://108818859

[dmgreen]

LGTM

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

ShrinkLoadReplaceStoreWithStore(const std::pair<unsigned, unsigned> &MaskInfo,
   bool UseTruncStore;
   if (DC->isTypeLegal(VT))
     UseTruncStore = false;
   else if (TLI.isTypeLegal(IVal.getValueType()) &&
            TLI.isTruncStoreLegal(IVal.getValueType(), VT))
     UseTruncStore = true;
   else
     return SDValue();
+
+  // Can't do this for indexed stores.
+  if (St->isIndexed())
+    return SDValue();
+
   // Check that the target doesn't think this is a bad idea.
   if (St->getMemOperand() &&
       !TLI.allowsMemoryAccess(*DAG.getContext(), DAG.getDataLayout(), VT,
                               *St->getMemOperand()))
     return SDValue();
 
   // Okay, we can do this!  Replace the 'St' store with a store of IVal that is
   // shifted by ByteShift and truncated down to NumBytes.

llvm/test/CodeGen/AArch64/replace-load-with-shrink-store-indexed-crash.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
+; RUN: llc < %s -mtriple=aarch64-- | FileCheck %s
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+target triple = "arm64-apple-macosx13.0.0"
+
+define void @_Z1hP1f(ptr %j) {
+; CHECK-LABEL: _Z1hP1f:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    mov x8, x0
+; CHECK-NEXT:  .LBB0_1: // %for.body
+; CHECK-NEXT:    // =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    ldr w9, [x8]
+; CHECK-NEXT:    mov w10, w9
+; CHECK-NEXT:    bfi w10, w9, #16, #16
+; CHECK-NEXT:    str w10, [x8], #4
+; CHECK-NEXT:    str w9, [x0]
+; CHECK-NEXT:    b .LBB0_1
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %indvars.iv1 = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %arrayidx3 = getelementptr i32, ptr %j, i64 %indvars.iv1
+  %0 = load i32, ptr %arrayidx3, align 4
+  %and = and i32 %0, 65535
+  %or = mul i32 %and, 65537
+  store i32 %or, ptr %arrayidx3, align 4
+  store i32 %0, ptr %j, align 4
+  %indvars.iv.next = add i64 %indvars.iv1, 1
+  br label %for.body
+}