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

[via cfe-commits]

https://github.com/eddyz87 updated https://github.com/llvm/llvm-project/pull/108071

>From 170f6a604b041bb33c5089dd84fd26de7bd2292e Mon Sep 17 00:00:00 2001
From: Eduard Zingerman <eddyz87 at gmail.com>
Date: Tue, 10 Sep 2024 11:11:58 -0700
Subject: [PATCH 1/2] [BPF] make __BPF_FEATURE_MAY_GOTO available for cpuv1

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.
---
 clang/lib/Basic/Targets/BPF.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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)

>From 5c025e2fec3288f55e7ebb537356b49052b0ce63 Mon Sep 17 00:00:00 2001
From: Eduard Zingerman <eddyz87 at gmail.com>
Date: Tue, 10 Sep 2024 12:33:02 -0700
Subject: [PATCH 2/2] [BPF] update bpf-predefined-macros.c to test
 __BPF_FEATURE_MAY_GOTO

<commit message would be squashed and is not relevant>
---
 clang/test/Preprocessor/bpf-predefined-macros.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/clang/test/Preprocessor/bpf-predefined-macros.c b/clang/test/Preprocessor/bpf-predefined-macros.c
index 360b9330b75fef..8c2143f767c40c 100644
--- a/clang/test/Preprocessor/bpf-predefined-macros.c
+++ b/clang/test/Preprocessor/bpf-predefined-macros.c
@@ -64,6 +64,9 @@ int s;
 #ifdef __BPF_FEATURE_ADDR_SPACE_CAST
 int t;
 #endif
+#ifdef __BPF_FEATURE_MAY_GOTO
+int u;
+#endif
 
 // CHECK: int b;
 // CHECK: int c;
@@ -98,6 +101,11 @@ int t;
 // CPU_V3: int t;
 // CPU_V4: int t;
 
+// CPU_V1: int u;
+// CPU_V2: int u;
+// CPU_V3: int u;
+// CPU_V4: int u;
+
 // CPU_GENERIC: int g;
 
 // CPU_PROBE: int f;