[clang] [llvm] [RISCV] Add support for getHostCPUFeatures using hwprobe (PR #94352)
Yangyu Chen via cfe-commits
cfe-commits at lists.llvm.org
Mon Jun 24 18:34:41 PDT 2024
================
@@ -2002,6 +2003,76 @@ bool sys::getHostCPUFeatures(StringMap<bool> &Features) {
return true;
}
+#elif defined(__linux__) && defined(__riscv)
+// struct riscv_hwprobe
+struct RISCVHwProbe {
+ int64_t Key;
+ uint64_t Value;
+};
+bool sys::getHostCPUFeatures(StringMap<bool> &Features) {
+ RISCVHwProbe Query[]{{/*RISCV_HWPROBE_KEY_BASE_BEHAVIOR=*/3, 0},
+ {/*RISCV_HWPROBE_KEY_IMA_EXT_0=*/4, 0}};
+ int Ret = syscall(/*__NR_riscv_hwprobe=*/258, /*pairs=*/Query,
+ /*pair_count=*/std::size(Query), /*cpu_count=*/0,
+ /*cpus=*/0, /*flags=*/0);
+ if (Ret != 0)
+ return false;
+
+ uint64_t BaseMask = Query[0].Value;
+ // Check whether RISCV_HWPROBE_BASE_BEHAVIOR_IMA is set.
+ if (BaseMask & 1) {
+ Features["i"] = true;
+ Features["m"] = true;
+ Features["a"] = true;
+ }
+
+ uint64_t ExtMask = Query[1].Value;
----------------
cyyself wrote:
I think this is not safe. The minimal ISA for RISC-V Linux is IMA. If someone modified the kernel to run on some CPUs without M or A extension(theoretically A can be replaced with Zalrsc), the base behavior probe will be zero but it doesn’t mean we have IMA.
https://github.com/llvm/llvm-project/pull/94352
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