[clang] [llvm] Add support for flag output operand "=@cc" for SystemZ. (PR #125970)

[Ulrich Weigand via cfe-commits]

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@@ -2715,18 +2716,20 @@ EmitAsmStores(CodeGenFunction &CGF, const AsmStmt &S,
   // ResultRegDests can be also populated by addReturnRegisterOutputs() above,
   // in which case its size may grow.
   assert(ResultTypeRequiresCast.size() <= ResultRegDests.size());
-  assert(ResultRegIsFlagReg.size() <= ResultRegDests.size());
+  assert(OutputOperandBounds.size() <= ResultRegDests.size());
 
   for (unsigned i = 0, e = RegResults.size(); i != e; ++i) {
     llvm::Value *Tmp = RegResults[i];
     llvm::Type *TruncTy = ResultTruncRegTypes[i];
 
-    if ((i < ResultRegIsFlagReg.size()) && ResultRegIsFlagReg[i]) {
-      // Target must guarantee the Value `Tmp` here is lowered to a boolean
-      // value.
-      llvm::Constant *Two = llvm::ConstantInt::get(Tmp->getType(), 2);
+    if ((i < OutputOperandBounds.size()) &&
+        OutputOperandBounds[i].has_value()) {
+      const auto [LowerBound, UpperBound] = OutputOperandBounds[i].value();
+      assert(LowerBound == 0 && "Output operand lower bound is not zero.");
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uweigand wrote:

There should be another comment here, along the lines of
```
// FIXME: Support for nonzero lower bounds not yet implemented.
```


https://github.com/llvm/llvm-project/pull/125970