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

[Ulrich Weigand via llvm-commits]

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@@ -98,6 +98,15 @@ bool SystemZTargetInfo::validateAsmConstraint(
   case 'T': // Likewise, plus an index
     Info.setAllowsMemory();
     return true;
+  case '@':
+    // CC condition changes.
+    if (StringRef(Name) == "@cc") {
+      Name += 2;
+      Info.setAllowsRegister();
+      Info.setFlagOutputCCUpperBound(4);
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uweigand wrote:

*Here* we should have the platform-specific comment explaining why this is 4.

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