[clang] [HLSL] Implement output parameter (PR #101083)

[John McCall via cfe-commits]

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@@ -4148,6 +4152,30 @@ static void emitWriteback(CodeGenFunction &CGF,
   assert(!isProvablyNull(srcAddr.getBasePointer()) &&
          "shouldn't have writeback for provably null argument");
 
+  if (CGF.getLangOpts().HLSL) {
+    if (!isa<OpaqueValueExpr>(writeback.CastExpr)) {
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rjmccall wrote:

You at least need a comment explaining what you're trying to do here.  It looks like you're trying to avoid potentially creating a temporary if there's no conversion required as part of the writeback?

https://github.com/llvm/llvm-project/pull/101083