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

[Ulrich Weigand via cfe-commits]

================
@@ -8701,95 +8734,341 @@ SDValue SystemZTargetLowering::combineSETCC(
   return SDValue();
 }
 
-static bool combineCCMask(SDValue &CCReg, int &CCValid, int &CCMask) {
+static std::pair<SDValue, int> findCCUse(const SDValue &Val) {
+  auto *N = Val.getNode();
+  if (!N)
+    return std::make_pair(SDValue(), SystemZ::CCMASK_NONE);
+  switch (N->getOpcode()) {
+  default:
+    return std::make_pair(SDValue(), SystemZ::CCMASK_NONE);
+  case SystemZISD::IPM:
+    if (N->getOperand(0).getOpcode() == SystemZISD::CLC ||
+        N->getOperand(0).getOpcode() == SystemZ::CLST ||
+        N->getOperand(0).getOpcode() == SystemZISD::STRCMP)
+      return std::make_pair(N->getOperand(0), SystemZ::CCMASK_ICMP);
+    return std::make_pair(N->getOperand(0), SystemZ::CCMASK_ANY);
+  case ISD::SHL:
+  case ISD::SRA:
+  case ISD::SRL:
----------------
uweigand wrote:

Actually, you could just treat these identical to the other binary operators 
below, and recurse into both operands.

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