[clang] [llvm] [HLSL] Adding Flatten and Branch if attributes (PR #116331)

[Chris B via cfe-commits]

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@@ -1206,6 +1202,21 @@ class SPIRVStructurizer : public FunctionPass {
     AU.addPreserved<SPIRVConvergenceRegionAnalysisWrapperPass>();
     FunctionPass::getAnalysisUsage(AU);
   }
+
+  void createOpSelectMerge(IRBuilder<> *Builder, BlockAddress *MergeAddress) {
+    Instruction *BBTerminatorInst = Builder->GetInsertBlock()->getTerminator();
+
+    MDNode *MDNode = BBTerminatorInst->getMetadata("hlsl.controlflow.hint");
+    if (MDNode)
+      assert(MDNode->getNumOperands() == 2 &&
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llvm-beanz wrote:

You shouldn't put an `assert` as the only statement on an `if` block, it is better to fold it into the assert condition.

Today most C runtimes are nice about the `assert` macro defining to a no-op statement because the spec defines it as such, but people do replace `assert`, and lots of horrible things can happen if a single-statement `if`'s body is a macro expansion and the macro doesn't expand to a complete statement. Things like the _next_ statement becoming the body of the `if`.

https://github.com/llvm/llvm-project/pull/116331