[clang] [Clang][CodeGen] Do not set inbounds flag in `EmitMemberDataPointerAddress` when the base pointer is null (PR #130952)

[Eli Friedman via cfe-commits]

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@@ -660,8 +660,8 @@ EmitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *M) {
 
     case SubobjectAdjustment::MemberPointerAdjustment: {
       llvm::Value *Ptr = EmitScalarExpr(Adjustment.Ptr.RHS);
-      Object = EmitCXXMemberDataPointerAddress(E, Object, Ptr,
-                                               Adjustment.Ptr.MPT);
+      Object = EmitCXXMemberDataPointerAddress(
+          E, Object, Ptr, Adjustment.Ptr.MPT, /*IsInBounds=*/true);
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efriedma-quic wrote:

This sent me down a really deep rabbit-hole to figure out when this code actually runs... apparently, in C++98 mode, we delay creating temporaries for things that would be xvalues in newer standard versions, and then we try to fix things up later using skipRValueSubobjectAdjustments().  We don't have an in-tree tests for this particular codepath.  The whole thing is really ugly, and we should really come up with a better solution...

In any case, the base object should be an alloca here, so inbounds should be fine.

https://github.com/llvm/llvm-project/pull/130952