Use the compiler to determine whether or not to enable `f16` and `f128`
Currently we whether or not to build and test `f16` and `f128` support
mostly based on the target triple. This isn't always accurate, however,
since support also varies by backend and the backend version.
Since recently, `rustc` is aware of this with the unstable config option
`target_has_reliable_{f16,f128}`, which better represents when the types
are actually expected to be available and usable. Switch our
compiler-builtins and libm configuration to use this by probing `rustc`
for the target's settings.
A few small `cfg` fixes are needed with this.
diff --git a/library/compiler-builtins/builtins-test-intrinsics/build.rs b/library/compiler-builtins/builtins-test-intrinsics/build.rs
index 89b126f..b825812 100644
--- a/library/compiler-builtins/builtins-test-intrinsics/build.rs
+++ b/library/compiler-builtins/builtins-test-intrinsics/build.rs
@@ -6,6 +6,5 @@ fn main() {
println!("cargo::rerun-if-changed=../configure.rs");
let target = builtins_configure::Target::from_env();
- builtins_configure::configure_f16_f128(&target);
builtins_configure::configure_aliases(&target);
}
diff --git a/library/compiler-builtins/builtins-test/benches/float_cmp.rs b/library/compiler-builtins/builtins-test/benches/float_cmp.rs
index 87a89ef..da29b5d 100644
--- a/library/compiler-builtins/builtins-test/benches/float_cmp.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_cmp.rs
@@ -177,6 +177,7 @@ fn gt_res_eq(mut a: CmpResult, mut b: CmpResult) -> bool {
],
}
+#[cfg(f128_enabled)]
float_bench! {
name: cmp_f128_gt,
sig: (a: f128, b: f128) -> CmpResult,
@@ -189,6 +190,7 @@ fn gt_res_eq(mut a: CmpResult, mut b: CmpResult) -> bool {
asm: []
}
+#[cfg(f128_enabled)]
float_bench! {
name: cmp_f128_unord,
sig: (a: f128, b: f128) -> CmpResult,
diff --git a/library/compiler-builtins/builtins-test/build.rs b/library/compiler-builtins/builtins-test/build.rs
index e8f4eb4..5b2dcd1 100644
--- a/library/compiler-builtins/builtins-test/build.rs
+++ b/library/compiler-builtins/builtins-test/build.rs
@@ -116,5 +116,4 @@ fn main() {
}
builtins_configure::configure_aliases(&target);
- builtins_configure::configure_f16_f128(&target);
}
diff --git a/library/compiler-builtins/builtins-test/tests/conv.rs b/library/compiler-builtins/builtins-test/tests/conv.rs
index 491915d..7d72936 100644
--- a/library/compiler-builtins/builtins-test/tests/conv.rs
+++ b/library/compiler-builtins/builtins-test/tests/conv.rs
@@ -118,7 +118,7 @@ fn $fn() {
i128, __floattidf;
}
- #[cfg(not(feature = "no-f16-f128"))]
+ #[cfg(f128_enabled)]
#[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc64")))]
i_to_f! { f128, Quad, not(feature = "no-sys-f128-int-convert"),
u32, __floatunsitf;
@@ -129,7 +129,7 @@ fn $fn() {
i128, __floattitf;
}
- #[cfg(not(feature = "no-f16-f128"))]
+ #[cfg(f128_enabled)]
#[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
i_to_f! { f128, Quad, not(feature = "no-sys-f128-int-convert"),
u32, __floatunsikf;
diff --git a/library/compiler-builtins/builtins-test/tests/div_rem.rs b/library/compiler-builtins/builtins-test/tests/div_rem.rs
index 5ae653c..e8327f9 100644
--- a/library/compiler-builtins/builtins-test/tests/div_rem.rs
+++ b/library/compiler-builtins/builtins-test/tests/div_rem.rs
@@ -147,7 +147,7 @@ mod float_div {
f64, __divdf3, Double, all();
}
- #[cfg(not(feature = "no-f16-f128"))]
+ #[cfg(f128_enabled)]
#[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc64")))]
float! {
f128, __divtf3, Quad,
@@ -156,7 +156,7 @@ mod float_div {
not(any(feature = "no-sys-f128", all(target_arch = "aarch64", target_os = "linux")));
}
- #[cfg(not(feature = "no-f16-f128"))]
+ #[cfg(f128_enabled)]
#[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
float! {
f128, __divkf3, Quad, not(feature = "no-sys-f128");
diff --git a/library/compiler-builtins/compiler-builtins/build.rs b/library/compiler-builtins/compiler-builtins/build.rs
index 018899f..8f51c12 100644
--- a/library/compiler-builtins/compiler-builtins/build.rs
+++ b/library/compiler-builtins/compiler-builtins/build.rs
@@ -2,7 +2,7 @@
use std::env;
-use configure::{Target, configure_aliases, configure_f16_f128};
+use configure::{Target, configure_aliases};
fn main() {
println!("cargo::rerun-if-changed=build.rs");
@@ -12,7 +12,6 @@ fn main() {
let cwd = env::current_dir().unwrap();
configure_check_cfg();
- configure_f16_f128(&target);
configure_aliases(&target);
configure_libm(&target);
diff --git a/library/compiler-builtins/compiler-builtins/configure.rs b/library/compiler-builtins/compiler-builtins/configure.rs
index d825f35..a1e4508 100644
--- a/library/compiler-builtins/compiler-builtins/configure.rs
+++ b/library/compiler-builtins/compiler-builtins/configure.rs
@@ -1,6 +1,7 @@
// Configuration that is shared between `compiler_builtins` and `builtins_test`.
-use std::env;
+use std::process::{Command, Stdio};
+use std::{env, str};
#[derive(Debug)]
#[allow(dead_code)]
@@ -16,6 +17,8 @@ pub struct Target {
pub pointer_width: u8,
pub little_endian: bool,
pub features: Vec<String>,
+ pub reliable_f128: bool,
+ pub reliable_f16: bool,
}
impl Target {
@@ -32,6 +35,19 @@ pub fn from_env() -> Self {
.map(|s| s.to_lowercase().replace("_", "-"))
.collect();
+ // Query rustc for options that Cargo does not provide env for. The bootstrap hack is used
+ // to get consistent output regardless of channel (`f16`/`f128` config options are hidden
+ // on stable otherwise).
+ let mut cmd = Command::new(env::var("RUSTC").unwrap());
+ cmd.args(["--print=cfg", "--target", &triple])
+ .env("RUSTC_BOOTSTRAP", "1")
+ .stderr(Stdio::inherit());
+ let out = cmd
+ .output()
+ .unwrap_or_else(|e| panic!("failed to run `{cmd:?}`: {e}"));
+ assert!(out.status.success(), "failed to run `{cmd:?}`");
+ let rustc_cfg = str::from_utf8(&out.stdout).unwrap();
+
Self {
triple,
triple_split,
@@ -51,6 +67,8 @@ pub fn from_env() -> Self {
.split(",")
.map(ToOwned::to_owned)
.collect(),
+ reliable_f128: rustc_cfg.lines().any(|l| l == "target_has_reliable_f128"),
+ reliable_f16: rustc_cfg.lines().any(|l| l == "target_has_reliable_f16"),
}
}
@@ -74,63 +92,24 @@ pub fn configure_aliases(target: &Target) {
if target.triple_split[0] == "thumbv6m" || target.triple_split[0] == "thumbv8m.base" {
println!("cargo:rustc-cfg=thumb_1")
}
-}
-/// Configure whether or not `f16` and `f128` support should be enabled.
-pub fn configure_f16_f128(target: &Target) {
- // Set whether or not `f16` and `f128` are supported at a basic level by LLVM. This only means
- // that the backend will not crash when using these types and generates code that can be called
- // without crashing (no infinite recursion). This does not mean that the platform doesn't have
- // ABI or other bugs.
- //
- // We do this here rather than in `rust-lang/rust` because configuring via cargo features is
- // not straightforward.
- //
- // Original source of this list:
- // <https://github.com/rust-lang/compiler-builtins/pull/652#issuecomment-2266151350>
- let f16_enabled = match target.arch.as_str() {
- // Unsupported <https://github.com/llvm/llvm-project/issues/94434>
- "arm64ec" => false,
- // Selection failure <https://github.com/llvm/llvm-project/issues/50374>
- "s390x" => false,
- // Infinite recursion <https://github.com/llvm/llvm-project/issues/97981>
- "csky" => false,
- "hexagon" => false,
- "powerpc" | "powerpc64" => false,
- "sparc" | "sparc64" => false,
- "wasm32" | "wasm64" => false,
- // Most everything else works as of LLVM 19
- _ => true,
- };
+ /* Not all backends support `f16` and `f128` to the same level on all architectures, so we
+ * need to disable things if the compiler may crash. See configuration at:
+ * * https://github.com/rust-lang/rust/blob/c65dccabacdfd6c8a7f7439eba13422fdd89b91e/compiler/rustc_codegen_llvm/src/llvm_util.rs#L367-L432
+ * * https://github.com/rust-lang/rustc_codegen_gcc/blob/4b5c44b14166083eef8d71f15f5ea1f53fc976a0/src/lib.rs#L496-L507
+ * * https://github.com/rust-lang/rustc_codegen_cranelift/blob/c713ffab3c6e28ab4b4dd4e392330f786ea657ad/src/lib.rs#L196-L226
+ */
- let f128_enabled = match target.arch.as_str() {
- // Unsupported (libcall is not supported) <https://github.com/llvm/llvm-project/issues/121122>
- "amdgpu" => false,
- // Unsupported <https://github.com/llvm/llvm-project/issues/94434>
- "arm64ec" => false,
- // FIXME(llvm20): fixed by <https://github.com/llvm/llvm-project/pull/117525>
- "mips64" | "mips64r6" => false,
- // Selection failure <https://github.com/llvm/llvm-project/issues/95471>
- "nvptx64" => false,
- // Selection failure <https://github.com/llvm/llvm-project/issues/101545>
- "powerpc64" if &target.os == "aix" => false,
- // Selection failure <https://github.com/llvm/llvm-project/issues/41838>
- "sparc" => false,
- // Most everything else works as of LLVM 19
- _ => true,
- };
-
- // If the feature is set, disable these types.
- let disable_both = env::var_os("CARGO_FEATURE_NO_F16_F128").is_some();
+ // If the feature is set, disable both of these types.
+ let no_f16_f128 = target.cargo_features.iter().any(|s| s == "no-f16-f128");
println!("cargo::rustc-check-cfg=cfg(f16_enabled)");
- println!("cargo::rustc-check-cfg=cfg(f128_enabled)");
-
- if f16_enabled && !disable_both {
+ if target.reliable_f16 && !no_f16_f128 {
println!("cargo::rustc-cfg=f16_enabled");
}
- if f128_enabled && !disable_both {
+ println!("cargo::rustc-check-cfg=cfg(f128_enabled)");
+ if target.reliable_f128 && !no_f16_f128 {
println!("cargo::rustc-cfg=f128_enabled");
}
}
diff --git a/library/compiler-builtins/libm/configure.rs b/library/compiler-builtins/libm/configure.rs
index 2a497c7..6562ecb 100644
--- a/library/compiler-builtins/libm/configure.rs
+++ b/library/compiler-builtins/libm/configure.rs
@@ -1,7 +1,8 @@
// Configuration shared with both libm and libm-test
-use std::env;
use std::path::PathBuf;
+use std::process::{Command, Stdio};
+use std::{env, str};
#[allow(dead_code)]
pub struct Config {
@@ -9,6 +10,7 @@ pub struct Config {
pub out_dir: PathBuf,
pub opt_level: String,
pub cargo_features: Vec<String>,
+ pub target_triple: String,
pub target_arch: String,
pub target_env: String,
pub target_family: Option<String>,
@@ -16,10 +18,13 @@ pub struct Config {
pub target_string: String,
pub target_vendor: String,
pub target_features: Vec<String>,
+ pub reliable_f128: bool,
+ pub reliable_f16: bool,
}
impl Config {
pub fn from_env() -> Self {
+ let target_triple = env::var("TARGET").unwrap();
let target_features = env::var("CARGO_CFG_TARGET_FEATURE")
.map(|feats| feats.split(',').map(ToOwned::to_owned).collect())
.unwrap_or_default();
@@ -28,7 +33,21 @@ pub fn from_env() -> Self {
.map(|s| s.to_lowercase().replace("_", "-"))
.collect();
+ // Query rustc for options that Cargo does not provide env for. The bootstrap hack is used
+ // to get consistent output regardless of channel (`f16`/`f128` config options are hidden
+ // on stable otherwise).
+ let mut cmd = Command::new(env::var("RUSTC").unwrap());
+ cmd.args(["--print=cfg", "--target", &target_triple])
+ .env("RUSTC_BOOTSTRAP", "1")
+ .stderr(Stdio::inherit());
+ let out = cmd
+ .output()
+ .unwrap_or_else(|e| panic!("failed to run `{cmd:?}`: {e}"));
+ assert!(out.status.success(), "failed to run `{cmd:?}`");
+ let rustc_cfg = str::from_utf8(&out.stdout).unwrap();
+
Self {
+ target_triple,
manifest_dir: PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap()),
out_dir: PathBuf::from(env::var("OUT_DIR").unwrap()),
opt_level: env::var("OPT_LEVEL").unwrap(),
@@ -40,6 +59,8 @@ pub fn from_env() -> Self {
target_string: env::var("TARGET").unwrap(),
target_vendor: env::var("CARGO_CFG_TARGET_VENDOR").unwrap(),
target_features,
+ reliable_f128: rustc_cfg.lines().any(|l| l == "target_has_reliable_f128"),
+ reliable_f16: rustc_cfg.lines().any(|l| l == "target_has_reliable_f16"),
}
}
}
@@ -128,62 +149,18 @@ fn emit_f16_f128_cfg(cfg: &Config) {
return;
}
- // Set whether or not `f16` and `f128` are supported at a basic level by LLVM. This only means
- // that the backend will not crash when using these types and generates code that can be called
- // without crashing (no infinite recursion). This does not mean that the platform doesn't have
- // ABI or other bugs.
- //
- // We do this here rather than in `rust-lang/rust` because configuring via cargo features is
- // not straightforward.
- //
- // Original source of this list:
- // <https://github.com/rust-lang/compiler-builtins/pull/652#issuecomment-2266151350>
- let f16_enabled = match cfg.target_arch.as_str() {
- // Unsupported <https://github.com/llvm/llvm-project/issues/94434>
- "arm64ec" => false,
- // Selection failure <https://github.com/llvm/llvm-project/issues/50374>
- "s390x" => false,
- // Infinite recursion <https://github.com/llvm/llvm-project/issues/97981>
- // FIXME(llvm): loongarch fixed by <https://github.com/llvm/llvm-project/pull/107791>
- "csky" => false,
- "hexagon" => false,
- "loongarch64" => false,
- "mips" | "mips64" | "mips32r6" | "mips64r6" => false,
- "powerpc" | "powerpc64" => false,
- "sparc" | "sparc64" => false,
- "wasm32" | "wasm64" => false,
- // Most everything else works as of LLVM 19
- _ => true,
- };
+ /* See the compiler-builtins configure file for info about the meaning of these options */
- let f128_enabled = match cfg.target_arch.as_str() {
- // Unsupported (libcall is not supported) <https://github.com/llvm/llvm-project/issues/121122>
- "amdgpu" => false,
- // Unsupported <https://github.com/llvm/llvm-project/issues/94434>
- "arm64ec" => false,
- // Selection failure <https://github.com/llvm/llvm-project/issues/96432>
- "mips64" | "mips64r6" => false,
- // Selection failure <https://github.com/llvm/llvm-project/issues/95471>
- "nvptx64" => false,
- // Selection failure <https://github.com/llvm/llvm-project/issues/101545>
- "powerpc64" if &cfg.target_os == "aix" => false,
- // Selection failure <https://github.com/llvm/llvm-project/issues/41838>
- "sparc" => false,
- // Most everything else works as of LLVM 19
- _ => true,
- };
-
- // If the feature is set, disable these types.
- let disable_both = env::var_os("CARGO_FEATURE_NO_F16_F128").is_some();
+ // If the feature is set, disable both of these types.
+ let no_f16_f128 = cfg.cargo_features.iter().any(|s| s == "no-f16-f128");
println!("cargo:rustc-check-cfg=cfg(f16_enabled)");
- println!("cargo:rustc-check-cfg=cfg(f128_enabled)");
-
- if f16_enabled && !disable_both {
+ if cfg.reliable_f16 && !no_f16_f128 {
println!("cargo:rustc-cfg=f16_enabled");
}
- if f128_enabled && !disable_both {
+ println!("cargo:rustc-check-cfg=cfg(f128_enabled)");
+ if cfg.reliable_f128 && !no_f16_f128 {
println!("cargo:rustc-cfg=f128_enabled");
}
}
