[compiler-rt] [SystemZ][XRay] Make xray work with gcc (PR #126154)

[Kai Nacke via llvm-commits]

https://github.com/redstar created https://github.com/llvm/llvm-project/pull/126154

It seems that depending on the platform, gcc acceptts or does not accept `-mvx` without specifying an architecture actually having vector instructions. The solution which seems to work across different versions of gcc and clang is to specify the least architecture which has vector instructions.

In addition, initialization of the unused variable CPU prevents a compiler warning from gcc.

>From c80128eeb07721315f98961e843f967e75695a28 Mon Sep 17 00:00:00 2001
From: Kai Nacke <kai.peter.nacke at ibm.com>
Date: Thu, 6 Feb 2025 18:24:55 -0500
Subject: [PATCH] [SystemZ][XRay] Make xray work with gcc

It seems that depending on the platform, gcc acceptts or does not
accept `-mvx` without specifying an architecture actually having
vector instructions. The solution which seems to work across
different versions of gcc and clang is to specify the least
architecture which has vector instructions.

In addition, initialization of the unused variable CPU prevents
a compiler warning from gcc.
---
 compiler-rt/lib/xray/CMakeLists.txt | 2 +-
 compiler-rt/lib/xray/xray_tsc.h     | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/compiler-rt/lib/xray/CMakeLists.txt b/compiler-rt/lib/xray/CMakeLists.txt
index 673091807e348de..c79b0b634ddf167 100644
--- a/compiler-rt/lib/xray/CMakeLists.txt
+++ b/compiler-rt/lib/xray/CMakeLists.txt
@@ -111,7 +111,7 @@ set(riscv64_SOURCES
   xray_trampoline_s390x.S
   )
 # Enable vector instructions in the assembly file.
-set_source_files_properties(xray_trampoline_s390x.S PROPERTIES COMPILE_FLAGS -mvx)
+set_source_files_properties(xray_trampoline_s390x.S PROPERTIES COMPILE_FLAGS -march=z13)
 
 set(XRAY_SOURCE_ARCHS
   arm
diff --git a/compiler-rt/lib/xray/xray_tsc.h b/compiler-rt/lib/xray/xray_tsc.h
index 118b6f00e33ea53..c8a8b2f16fef84a 100644
--- a/compiler-rt/lib/xray/xray_tsc.h
+++ b/compiler-rt/lib/xray/xray_tsc.h
@@ -96,6 +96,7 @@ namespace __xray {
 inline bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT { return true; }
 
 ALWAYS_INLINE uint64_t readTSC(uint8_t &CPU) XRAY_NEVER_INSTRUMENT {
+  CPU = 0;
 #if __has_builtin(__builtin_readcyclecounter)
   return __builtin_readcyclecounter();
 #else