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Target stack-probe support configurable finely

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This adds capability to configure the target's stack probe support in a
more precise manner than just on/off. In particular now we allow
choosing between always inline-asm, always call or either one of those
depending on the LLVM version on a per-target basis.
This commit is contained in:
Simonas Kazlauskas 2021-01-09 16:54:20 +02:00
parent efdb859dcd
commit 007080b607
35 changed files with 203 additions and 87 deletions
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45
compiler/rustc_codegen_llvm/src/attributes.rs
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@ -13,6 +13,7 @@ use rustc_middle::ty::query::Providers;
use rustc_middle::ty::{self, TyCtxt};
use rustc_session::config::{OptLevel, SanitizerSet};
use rustc_session::Session;
use rustc_target::spec::StackProbeType;
use crate::attributes;
use crate::llvm::AttributePlace::Function;
@ -98,12 +99,6 @@ fn set_instrument_function(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
}
fn set_probestack(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
// Only use stack probes if the target specification indicates that we
// should be using stack probes
if !cx.sess().target.stack_probes {
return;
}
// Currently stack probes seem somewhat incompatible with the address
// sanitizer and thread sanitizer. With asan we're already protected from
// stack overflow anyway so we don't really need stack probes regardless.
@ -127,19 +122,31 @@ fn set_probestack(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
return;
}
llvm::AddFunctionAttrStringValue(
llfn,
llvm::AttributePlace::Function,
const_cstr!("probe-stack"),
if llvm_util::get_version() < (11, 0, 1) {
// Flag our internal `__rust_probestack` function as the stack probe symbol.
// This is defined in the `compiler-builtins` crate for each architecture.
const_cstr!("__rust_probestack")
} else {
// On LLVM 11+, emit inline asm for stack probes instead of a function call.
const_cstr!("inline-asm")
},
);
let attr_value = match cx.sess().target.stack_probes {
StackProbeType::None => None,
// Request LLVM to generate the probes inline. If the given LLVM version does not support
// this, no probe is generated at all (even if the attribute is specified).
StackProbeType::Inline => Some(const_cstr!("inline-asm")),
// Flag our internal `__rust_probestack` function as the stack probe symbol.
// This is defined in the `compiler-builtins` crate for each architecture.
StackProbeType::Call => Some(const_cstr!("__rust_probestack")),
// Pick from the two above based on the LLVM version.
StackProbeType::InlineOrCall { min_llvm_version_for_inline } => {
if llvm_util::get_version() < min_llvm_version_for_inline {
Some(const_cstr!("__rust_probestack"))
} else {
Some(const_cstr!("inline-asm"))
}
}
};
if let Some(attr_value) = attr_value {
llvm::AddFunctionAttrStringValue(
llfn,
llvm::AttributePlace::Function,
const_cstr!("probe-stack"),
attr_value,
);
}
}
pub fn llvm_target_features(sess: &Session) -> impl Iterator<Item = &str> {