[clang] [BPF] make __BPF_FEATURE_MAY_GOTO available for cpuv1 (PR #108071)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (eddyz87)

<details>
<summary>Changes</summary>

For some reason `__BPF_FEATURE_MAY_GOTO` is available for CPUs v{2,3,4} but is not available for CPU v1. This limitation is arbitrary:
- the instruction is never produced by LLVM backend;
- on Linux Kernel side this instruction is available in kernels that also support CPUv4.

Hence, it is more consistent to either always allow `__BPF_FEATURE_MAY_GOTO` or only allow it for CPUv4.

---
Full diff: https://github.com/llvm/llvm-project/pull/108071.diff


1 Files Affected:

- (modified) clang/lib/Basic/Targets/BPF.cpp (+1-1) 


``````````diff
diff --git a/clang/lib/Basic/Targets/BPF.cpp b/clang/lib/Basic/Targets/BPF.cpp
index a94ceee5a6a5e7..931f407ecb0d7e 100644
--- a/clang/lib/Basic/Targets/BPF.cpp
+++ b/clang/lib/Basic/Targets/BPF.cpp
@@ -37,6 +37,7 @@ void BPFTargetInfo::getTargetDefines(const LangOptions &Opts,
   }
 
   Builder.defineMacro("__BPF_FEATURE_ADDR_SPACE_CAST");
+  Builder.defineMacro("__BPF_FEATURE_MAY_GOTO");
 
   if (CPU.empty())
     CPU = "v3";
@@ -48,7 +49,6 @@ void BPFTargetInfo::getTargetDefines(const LangOptions &Opts,
 
   std::string CpuVerNumStr = CPU.substr(1);
   Builder.defineMacro("__BPF_CPU_VERSION__", CpuVerNumStr);
-  Builder.defineMacro("__BPF_FEATURE_MAY_GOTO");
 
   int CpuVerNum = std::stoi(CpuVerNumStr);
   if (CpuVerNum >= 2)

``````````

</details>


https://github.com/llvm/llvm-project/pull/108071