[compiler-rt] [XRay][SystemZ] Use stckf for non-clang compilers (PR #125289)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-xray

Author: Kai Nacke (redstar)

<details>
<summary>Changes</summary>

Turns out there are users who use gcc to compile compiler-rt. Using the clang-specific builtin function `__builtin_readcyclecounter()` does not work in this case.
Solution is to use inline assembly using the stckf instruction in case the compiler is not clang.

---
Full diff: https://github.com/llvm/llvm-project/pull/125289.diff


1 Files Affected:

- (modified) compiler-rt/lib/xray/xray_tsc.h (+6) 


``````````diff
diff --git a/compiler-rt/lib/xray/xray_tsc.h b/compiler-rt/lib/xray/xray_tsc.h
index 17e06c7035d85c..06f509cd1b09b9 100644
--- a/compiler-rt/lib/xray/xray_tsc.h
+++ b/compiler-rt/lib/xray/xray_tsc.h
@@ -96,7 +96,13 @@ namespace __xray {
 inline bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT { return true; }
 
 ALWAYS_INLINE uint64_t readTSC(uint8_t &CPU) XRAY_NEVER_INSTRUMENT {
+#if defined(__clang__)
   return __builtin_readcyclecounter();
+#else
+  uint64_t Cycles;
+  asm volatile("stckf %0" : /* No output. */ : "Q"(Cycles) : "cc");
+  return Cycles;
+#endif
 }
 
 inline uint64_t getTSCFrequency() XRAY_NEVER_INSTRUMENT {

``````````

</details>


https://github.com/llvm/llvm-project/pull/125289