[clang] [HLSL] Update indexed vector elements individually (PR #169144)

[Justin Bogner via cfe-commits]

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@@ -2575,6 +2575,30 @@ void CodeGenFunction::EmitStoreThroughLValue(RValue Src, LValue Dst,
                                              bool isInit) {
   if (!Dst.isSimple()) {
     if (Dst.isVectorElt()) {
+      if (getLangOpts().HLSL) {
+        // In HLSL, storing to individual elements of a vector through
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bogner wrote:

While it's true that HLSL doesn't really allow anything problematic, it might be worth an `assert` that `ElemTy->getScalarSizeInBits()` is at least byte sized in case something in the language changes down the road.

https://github.com/llvm/llvm-project/pull/169144