diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs index 09ece6164ebd1..64ebe585dd837 100644 --- a/compiler/rustc_codegen_llvm/src/attributes.rs +++ b/compiler/rustc_codegen_llvm/src/attributes.rs @@ -152,18 +152,6 @@ fn set_probestack(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) { } } -pub fn llvm_target_features(sess: &Session) -> impl Iterator { - const RUSTC_SPECIFIC_FEATURES: &[&str] = &["crt-static"]; - - let cmdline = sess - .opts - .cg - .target_feature - .split(',') - .filter(|f| !RUSTC_SPECIFIC_FEATURES.iter().any(|s| f.contains(s))); - sess.target.features.split(',').chain(cmdline).filter(|l| !l.is_empty()) -} - pub fn apply_target_cpu_attr(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) { let target_cpu = SmallCStr::new(llvm_util::target_cpu(cx.tcx.sess)); llvm::AddFunctionAttrStringValue( @@ -301,20 +289,22 @@ pub fn from_fn_attrs(cx: &CodegenCx<'ll, 'tcx>, llfn: &'ll Value, instance: ty:: // The target doesn't care; the subtarget reads our attribute. apply_tune_cpu_attr(cx, llfn); - let features = llvm_target_features(cx.tcx.sess) - .map(|s| s.to_string()) - .chain(codegen_fn_attrs.target_features.iter().map(|f| { + let function_features = codegen_fn_attrs + .target_features + .iter() + .map(|f| { let feature = &f.as_str(); format!("+{}", llvm_util::to_llvm_feature(cx.tcx.sess, feature)) - })) + }) .chain(codegen_fn_attrs.instruction_set.iter().map(|x| match x { InstructionSetAttr::ArmA32 => "-thumb-mode".to_string(), InstructionSetAttr::ArmT32 => "+thumb-mode".to_string(), })) - .collect::>() - .join(","); - - if !features.is_empty() { + .collect::>(); + if !function_features.is_empty() { + let mut global_features = llvm_util::llvm_global_features(cx.tcx.sess); + global_features.extend(function_features.into_iter()); + let features = global_features.join(","); let val = CString::new(features).unwrap(); llvm::AddFunctionAttrStringValue( llfn, diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs index c224da7885bd0..d33cb67e4033a 100644 --- a/compiler/rustc_codegen_llvm/src/back/write.rs +++ b/compiler/rustc_codegen_llvm/src/back/write.rs @@ -1,4 +1,3 @@ -use crate::attributes; use crate::back::lto::ThinBuffer; use crate::back::profiling::{ selfprofile_after_pass_callback, selfprofile_before_pass_callback, LlvmSelfProfiler, @@ -166,8 +165,6 @@ pub fn target_machine_factory( let code_model = to_llvm_code_model(sess.code_model()); - let mut features = llvm_util::handle_native_features(sess); - features.extend(attributes::llvm_target_features(sess).map(|s| s.to_owned())); let mut singlethread = sess.target.singlethread; // On the wasm target once the `atomics` feature is enabled that means that @@ -182,7 +179,7 @@ pub fn target_machine_factory( let triple = SmallCStr::new(&sess.target.llvm_target); let cpu = SmallCStr::new(llvm_util::target_cpu(sess)); - let features = features.join(","); + let features = llvm_util::llvm_global_features(sess).join(","); let features = CString::new(features).unwrap(); let abi = SmallCStr::new(&sess.target.llvm_abiname); let trap_unreachable = diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs index 544ef38c12c6d..c7dff41955ecc 100644 --- a/compiler/rustc_codegen_llvm/src/llvm_util.rs +++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs @@ -218,13 +218,39 @@ pub fn target_cpu(sess: &Session) -> &str { handle_native(name) } -pub fn handle_native_features(sess: &Session) -> Vec { +/// The list of LLVM features computed from CLI flags (`-Ctarget-cpu`, `-Ctarget-feature`, +/// `--target` and similar). +// FIXME(nagisa): Cache the output of this somehow? Maybe make this a query? We're calling this +// for every function that has `#[target_feature]` on it. The global features won't change between +// the functions; only crates, maybe… +pub fn llvm_global_features(sess: &Session) -> Vec { + // FIXME(nagisa): this should definitely be available more centrally and to other codegen backends. + /// These features control behaviour of rustc rather than llvm. + const RUSTC_SPECIFIC_FEATURES: &[&str] = &["crt-static"]; + + // Features that come earlier are overriden by conflicting features later in the string. + // Typically we'll want more explicit settings to override the implicit ones, so: + // + // * Features from -Ctarget-cpu=*; are overriden by [^1] + // * Features implied by --target; are overriden by + // * Features from -Ctarget-feature; are overriden by + // * function specific features. + // + // [^1]: target-cpu=native is handled here, other target-cpu values are handled implicitly + // through LLVM TargetMachine implementation. + // + // FIXME(nagisa): it isn't clear what's the best interaction between features implied by + // `-Ctarget-cpu` and `--target` are. On one hand, you'd expect CLI arguments to always + // override anything that's implicit, so e.g. when there's no `--target` flag, features implied + // the host target are overriden by `-Ctarget-cpu=*`. On the other hand, what about when both + // `--target` and `-Ctarget-cpu=*` are specified? Both then imply some target features and both + // flags are specified by the user on the CLI. It isn't as clear-cut which order of precedence + // should be taken in cases like these. + let mut features = vec![]; + + // -Ctarget-cpu=native match sess.opts.cg.target_cpu { - Some(ref s) => { - if s != "native" { - return vec![]; - } - + Some(ref s) if s == "native" => { let features_string = unsafe { let ptr = llvm::LLVMGetHostCPUFeatures(); let features_string = if !ptr.is_null() { @@ -242,11 +268,31 @@ pub fn handle_native_features(sess: &Session) -> Vec { features_string }; - - features_string.split(",").map(|s| s.to_owned()).collect() + features.extend(features_string.split(",").map(String::from)); } - None => vec![], - } + Some(_) | None => {} + }; + + // Features implied by an implicit or explicit `--target`. + features.extend( + sess.target + .features + .split(',') + .filter(|f| !f.is_empty() && !RUSTC_SPECIFIC_FEATURES.iter().any(|s| f.contains(s))) + .map(String::from), + ); + + // -Ctarget-features + features.extend( + sess.opts + .cg + .target_feature + .split(',') + .filter(|f| !f.is_empty() && !RUSTC_SPECIFIC_FEATURES.iter().any(|s| f.contains(s))) + .map(String::from), + ); + + features } pub fn tune_cpu(sess: &Session) -> Option<&str> { diff --git a/src/test/assembly/target-feature-multiple.rs b/src/test/assembly/target-feature-multiple.rs new file mode 100644 index 0000000000000..4c2073678b842 --- /dev/null +++ b/src/test/assembly/target-feature-multiple.rs @@ -0,0 +1,41 @@ +// assembly-output: emit-asm +// needs-llvm-components: x86 +// revisions: TWOFLAGS SINGLEFLAG +// compile-flags: --target=x86_64-unknown-linux-gnu +// [TWOFLAGS] compile-flags: -C target-feature=+rdrnd -C target-feature=+rdseed +// [SINGLEFLAG] compile-flags: -C target-feature=+rdrnd,+rdseed + +// Target features set via flags aren't necessarily reflected in the IR, so the only way to test +// them is to build code that requires the features to be enabled to work. +// +// In this particular test if `rdrnd,rdseed` somehow didn't make it to LLVM, the instruction +// selection should crash. +// +// > LLVM ERROR: Cannot select: 0x7f00f400c010: i32,i32,ch = X86ISD::RDSEED 0x7f00f400bfa8:2 +// > In function: foo +// +// See also src/test/codegen/target-feature-overrides.rs +#![feature(no_core, lang_items, link_llvm_intrinsics, abi_unadjusted)] +#![crate_type = "lib"] +#![no_core] + +#[lang = "sized"] +trait Sized {} +#[lang = "copy"] +trait Copy {} + +// Use of these requires target features to be enabled +extern "unadjusted" { + #[link_name = "llvm.x86.rdrand.32"] + fn x86_rdrand32_step() -> (u32, i32); + #[link_name = "llvm.x86.rdseed.32"] + fn x86_rdseed32_step() -> (u32, i32); +} + +#[no_mangle] +pub unsafe fn foo() -> (u32, u32) { + // CHECK-LABEL: foo: + // CHECK: rdrand + // CHECK: rdseed + (x86_rdrand32_step().0, x86_rdseed32_step().0) +} diff --git a/src/test/codegen/target-feature-multiple.rs b/src/test/codegen/target-feature-multiple.rs deleted file mode 100644 index f71a9c3c58216..0000000000000 --- a/src/test/codegen/target-feature-multiple.rs +++ /dev/null @@ -1,9 +0,0 @@ -// only-x86_64 -// compile-flags: -C target-feature=+sse2,-avx,+avx2 -C target-feature=+avx,-avx2 - -#![crate_type = "lib"] - -#[no_mangle] -pub fn foo() { - // CHECK: attributes #0 = { {{.*}}"target-features"="+sse2,-avx,+avx2,+avx,-avx2"{{.*}} } -} diff --git a/src/test/codegen/target-feature-on-functions.rs b/src/test/codegen/target-feature-on-functions.rs deleted file mode 100644 index d4d39d08b1eaa..0000000000000 --- a/src/test/codegen/target-feature-on-functions.rs +++ /dev/null @@ -1,9 +0,0 @@ -// only-x86_64 -// compile-flags: -C target-feature=+avx - -#![crate_type = "lib"] - -#[no_mangle] -pub fn foo() { - // CHECK: attributes #0 = { {{.*}}"target-features"="+avx"{{.*}} } -} diff --git a/src/test/codegen/target-feature-overrides.rs b/src/test/codegen/target-feature-overrides.rs new file mode 100644 index 0000000000000..2c19cfd8c2201 --- /dev/null +++ b/src/test/codegen/target-feature-overrides.rs @@ -0,0 +1,47 @@ +// revisions: COMPAT INCOMPAT +// needs-llvm-components: x86 +// compile-flags: --target=x86_64-unknown-linux-gnu -Copt-level=3 +// [COMPAT] compile-flags: -Ctarget-feature=+avx2,+avx +// [INCOMPAT] compile-flags: -Ctarget-feature=-avx2,-avx + +// See also src/test/assembly/target-feature-multiple.rs +#![feature(no_core, lang_items)] +#![crate_type = "lib"] +#![no_core] + + +#[lang = "sized"] +trait Sized {} +#[lang = "copy"] +trait Copy {} + +extern "C" { + fn peach() -> u32; +} + +#[inline] +#[target_feature(enable = "avx")] +#[no_mangle] +pub unsafe fn apple() -> u32 { +// CHECK-LABEL: @apple() +// CHECK-SAME: [[APPLEATTRS:#[0-9]+]] { +// CHECK: {{.*}}call{{.*}}@peach + peach() +} + +// target features same as global (not reflected or overriden in IR) +#[no_mangle] +pub unsafe fn banana() -> u32 { +// CHECK-LABEL: @banana() +// CHECK-SAME: [[BANANAATTRS:#[0-9]+]] { +// COMPAT: {{.*}}call{{.*}}@peach +// INCOMPAT: {{.*}}call{{.*}}@apple + apple() // Compatible for inline in COMPAT revision and can't be inlined in INCOMPAT +} + +// CHECK: attributes [[APPLEATTRS]] +// COMPAT-SAME: "target-features"="+avx2,+avx,+avx" +// INCOMPAT-SAME: "target-features"="-avx2,-avx,+avx" +// CHECK: attributes [[BANANAATTRS]] +// CHECK-NOT: target-features +// CHECK-SAME: }