[clang] [llvm] [SystemZ] Global Stackprotector and associated location section (PR #169317)

[Dominik Steenken via cfe-commits]

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@@ -8891,6 +8964,43 @@ SDValue SystemZTargetLowering::combineBR_CCMASK(SDNode *N,
                        DAG.getTargetConstant(CCValidVal, SDLoc(N), MVT::i32),
                        DAG.getTargetConstant(CCMaskVal, SDLoc(N), MVT::i32),
                        N->getOperand(3), CCReg);
+
+  SDLoc DL(N);
+
+  // Combine BR_CCMASK (ICMP (Load FI, Load StackGuard)) into BRC
+  // (COMPARE_STACK_GUARD)
+  int FI = 0;
+  SDValue InChain, OutChain, StackGuardLoad;
+  if (isStackGuardCheck(N, FI, InChain, OutChain, StackGuardLoad, DCI)) {
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dominik-steenken wrote:

That was the way i tried to do it initially - replacing `ICMP` with `COMPARE_STACK_GUARD` seemed to make the most sense. .But i had a lot of trouble getting the cc def/use to work. Ultimately, it was easier to do it on the branch, so that i could manually make that link. It's been a while, so i am a bit fuzzy on the details.

I will try the third way you mentioned now, though. If i can emit `COMPARE_STACK_GUARD_DAG` in `getCmp`, and the whole machinery after that just works, that would be ideal.

https://github.com/llvm/llvm-project/pull/169317