[llvm] 832ceda - [SystemZ] Avoid modifying IR in mcount instrumentation. (#152298)

[via llvm-commits]

Author: Dominik Steenken
Date: 2025-08-06T17:54:44+02:00
New Revision: 832ceda0c05f6db440a220860b3006f967f3bfd0

URL: https://github.com/llvm/llvm-project/commit/832ceda0c05f6db440a220860b3006f967f3bfd0
DIFF: https://github.com/llvm/llvm-project/commit/832ceda0c05f6db440a220860b3006f967f3bfd0.diff

LOG: [SystemZ] Avoid modifying IR in mcount instrumentation. (#152298)

This PR changes how the call to `mcount` is inserted in `emitPrologue`.
It is now emitted as an external symbol rather than a global variable,
preventing potentially unexpected IR modification.

Fixes: https://github.com/llvm/llvm-project/issues/152238

Added: 
    

Modified: 
    llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
index 6297916310803..5ee66e3dfa7a8 100644
--- a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
@@ -574,13 +574,11 @@ void SystemZELFFrameLowering::emitPrologue(MachineFunction &MF,
 
     // Call mcount (Regmask from CC AnyReg since mcount preserves all normal
     // argument registers).
-    FunctionCallee FC = MF.getFunction().getParent()->getOrInsertFunction(
-        "mcount", Type::getVoidTy(MF.getFunction().getContext()));
     const uint32_t *Mask = MF.getSubtarget<SystemZSubtarget>()
                                .getSpecialRegisters()
                                ->getCallPreservedMask(MF, CallingConv::AnyReg);
     BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::CallBRASL))
-        .addGlobalAddress(dyn_cast<Function>(FC.getCallee()))
+        .addExternalSymbol("mcount")
         .addRegMask(Mask);
 
     // Reload return address from 8 bytes above stack pointer.