gemini-code-assist[bot] commented on code in PR #19877:
URL: https://github.com/apache/tvm/pull/19877#discussion_r3462254280
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src/target/llvm/llvm_instance.cc:
##########
@@ -199,13 +277,26 @@ LLVMTargetInfo::LLVMTargetInfo(LLVMInstance& instance,
if (triple_.empty() || triple_ == "default") {
triple_ = llvm::sys::getDefaultTargetTriple();
}
+ bool has_explicit_mcpu = target.Get("mcpu").has_value();
cpu_ =
Downcast<ffi::String>(target.Get("mcpu").value_or(ffi::String(defaults::cpu)));
+ bool has_explicit_mattr = false;
if (const auto& v =
Downcast<ffi::Optional<ffi::Array<ffi::String>>>(target.Get("mattr"))) {
+ has_explicit_mattr = true;
for (const ffi::String& s : v.value()) {
attrs_.push_back(s);
}
}
+
+ auto arch = llvm::Triple(triple_).getArch();
+ if (!has_explicit_mattr && !has_explicit_mcpu &&
+ (arch == llvm::Triple::riscv32 || arch == llvm::Triple::riscv64)) {
+ std::vector<std::string> detected_attrs = DetectLocalRISCVAttrs();
+ for (const std::string& attr : detected_attrs) {
+ attrs_.push_back(attr);
+ }
+ }
Review Comment:
Automatically detecting and applying local CPU features when `mcpu` and
`mattr` are not specified is a great feature, but it should only be done when
targeting the host machine. If a user is cross-compiling on a RISC-V host for a
different RISC-V target (for example, compiling for a 32-bit bare-metal target
`riscv32-unknown-elf` from a 64-bit RISC-V Linux host), detecting and applying
the host's 64-bit features (like double-precision float `+d` or vector
extensions `+v`) will result in generating unsupported instructions for the
target device.
To prevent this, we should verify that the target triple's architecture and
OS match the host's architecture and OS before applying local CPU features.
```c
llvm::Triple target_triple(triple_);
auto arch = target_triple.getArch();
llvm::Triple host_triple(llvm::sys::getDefaultTargetTriple());
if (!has_explicit_mattr && !has_explicit_mcpu &&
arch == host_triple.getArch() &&
target_triple.getOS() == host_triple.getOS() &&
(arch == llvm::Triple::riscv32 || arch == llvm::Triple::riscv64)) {
std::vector<std::string> detected_attrs = DetectLocalRISCVAttrs();
for (const std::string& attr : detected_attrs) {
attrs_.push_back(attr);
}
}
```
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