test: Turn `feature = "no-sys-f128"` and similar into plain cfg These are internal configuration that Cargo doesn't need to be aware of. Clean them up from the Cargo.toml feature list.

diff --git a/library/compiler-builtins/builtins-test/Cargo.toml b/library/compiler-builtins/builtins-test/Cargo.toml
index 7f85842..1b356b1 100644
--- a/library/compiler-builtins/builtins-test/Cargo.toml
+++ b/library/compiler-builtins/builtins-test/Cargo.toml

@@ -27,14 +27,6 @@
 default = []
 c = ["compiler_builtins/c"]
 no-asm = ["compiler_builtins/no-asm"]
-# Skip tests that rely on f128 symbols being available on the system
-no-sys-f128 = ["no-sys-f128-int-convert", "no-sys-f16-f128-convert"]
-# Some platforms have some f128 functions but everything except integer conversions
-no-sys-f128-int-convert = []
-no-sys-f16-f128-convert = []
-no-sys-f16-f64-convert = []
-# Skip tests that rely on f16 symbols being available on the system
-no-sys-f16 = ["no-sys-f16-f64-convert"]
 
 # Enable icount benchmarks (requires gungraun-runner and valgrind locally)
 icount = ["dep:gungraun"]

diff --git a/library/compiler-builtins/builtins-test/benches/float_add.rs b/library/compiler-builtins/builtins-test/benches/float_add.rs
index 197f90b..2c1d2d9 100644
--- a/library/compiler-builtins/builtins-test/benches/float_add.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_add.rs

@@ -74,7 +74,7 @@
     crate_fn_ppc: add::__addkf3,
     sys_fn: __addtf3,
     sys_fn_ppc: __addkf3,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     asm: []
 }
 

diff --git a/library/compiler-builtins/builtins-test/benches/float_cmp.rs b/library/compiler-builtins/builtins-test/benches/float_cmp.rs
index da29b5d..cb13ce1 100644
--- a/library/compiler-builtins/builtins-test/benches/float_cmp.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_cmp.rs

@@ -185,7 +185,7 @@ fn gt_res_eq(mut a: CmpResult, mut b: CmpResult) -> bool {
     crate_fn_ppc: cmp::__gtkf2,
     sys_fn: __gttf2,
     sys_fn_ppc: __gtkf2,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     output_eq: gt_res_eq,
     asm: []
 }
@@ -198,7 +198,7 @@ fn gt_res_eq(mut a: CmpResult, mut b: CmpResult) -> bool {
     crate_fn_ppc: cmp::__unordkf2,
     sys_fn: __unordtf2,
     sys_fn_ppc: __unordkf2,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     asm: []
 }
 

diff --git a/library/compiler-builtins/builtins-test/benches/float_conv.rs b/library/compiler-builtins/builtins-test/benches/float_conv.rs
index 40c13d2..3525564 100644
--- a/library/compiler-builtins/builtins-test/benches/float_conv.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_conv.rs

@@ -84,7 +84,7 @@
     crate_fn_ppc: conv::__floatunsikf,
     sys_fn: __floatunsitf,
     sys_fn_ppc: __floatunsikf,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -138,7 +138,7 @@
     crate_fn_ppc: conv::__floatundikf,
     sys_fn: __floatunditf,
     sys_fn_ppc: __floatundikf,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -168,7 +168,7 @@
     crate_fn_ppc: conv::__floatuntikf,
     sys_fn: __floatuntitf,
     sys_fn_ppc: __floatuntikf,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -249,7 +249,7 @@
     crate_fn_ppc: conv::__floatsikf,
     sys_fn: __floatsitf,
     sys_fn_ppc: __floatsikf,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -328,7 +328,7 @@
     crate_fn_ppc: conv::__floatdikf,
     sys_fn: __floatditf,
     sys_fn_ppc: __floatdikf,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -358,7 +358,7 @@
     crate_fn_ppc: conv::__floattikf,
     sys_fn: __floattitf,
     sys_fn_ppc: __floattikf,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -473,7 +473,7 @@
     crate_fn: conv::__fixunstfsi,
     crate_fn_ppc: conv::__fixunskfsi,
     sys_fn: __fixunstfsi,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -484,7 +484,7 @@
     crate_fn: conv::__fixunstfdi,
     crate_fn_ppc: conv::__fixunskfdi,
     sys_fn: __fixunstfdi,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -495,7 +495,7 @@
     crate_fn: conv::__fixunstfti,
     crate_fn_ppc: conv::__fixunskfti,
     sys_fn: __fixunstfti,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -610,7 +610,7 @@
     crate_fn: conv::__fixtfsi,
     crate_fn_ppc: conv::__fixkfsi,
     sys_fn: __fixtfsi,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -621,7 +621,7 @@
     crate_fn: conv::__fixtfdi,
     crate_fn_ppc: conv::__fixkfdi,
     sys_fn: __fixtfdi,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 
@@ -632,7 +632,7 @@
     crate_fn: conv::__fixtfti,
     crate_fn_ppc: conv::__fixkfti,
     sys_fn: __fixtfti,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: []
 }
 

diff --git a/library/compiler-builtins/builtins-test/benches/float_div.rs b/library/compiler-builtins/builtins-test/benches/float_div.rs
index d5b0ad0..dd2b2c1 100644
--- a/library/compiler-builtins/builtins-test/benches/float_div.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_div.rs

@@ -74,7 +74,7 @@
     crate_fn_ppc: div::__divkf3,
     sys_fn: __divtf3,
     sys_fn_ppc: __divkf3,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     asm: []
 }
 

diff --git a/library/compiler-builtins/builtins-test/benches/float_extend.rs b/library/compiler-builtins/builtins-test/benches/float_extend.rs
index 939dc60..7896d10 100644
--- a/library/compiler-builtins/builtins-test/benches/float_extend.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_extend.rs

@@ -12,7 +12,7 @@
     sig: (a: f16) -> f32,
     crate_fn: extend::__extendhfsf2,
     sys_fn: __extendhfsf2,
-    sys_available: not(feature = "no-sys-f16"),
+    sys_available: not(no_sys_f16),
     asm: [
         #[cfg(target_arch = "aarch64")] {
             let ret: f32;
@@ -34,7 +34,7 @@
     sig: (a: f16) -> f64,
     crate_fn: extend::__extendhfdf2,
     sys_fn: __extendhfdf2,
-    sys_available: not(feature = "no-sys-f16-f64-convert"),
+    sys_available: not(no_sys_f16_f64_convert),
     asm: [
         #[cfg(target_arch = "aarch64")] {
             let ret: f64;
@@ -58,7 +58,7 @@
     crate_fn_ppc: extend::__extendhfkf2,
     sys_fn: __extendhftf2,
     sys_fn_ppc: __extendhfkf2,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: [],
 }
 
@@ -91,7 +91,7 @@
     crate_fn_ppc: extend::__extendsfkf2,
     sys_fn: __extendsftf2,
     sys_fn_ppc: __extendsfkf2,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     asm: [],
 }
 
@@ -103,7 +103,7 @@
     crate_fn_ppc: extend::__extenddfkf2,
     sys_fn: __extenddftf2,
     sys_fn_ppc: __extenddfkf2,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     asm: [],
 }
 

diff --git a/library/compiler-builtins/builtins-test/benches/float_mul.rs b/library/compiler-builtins/builtins-test/benches/float_mul.rs
index a7a2d34..54fc6da 100644
--- a/library/compiler-builtins/builtins-test/benches/float_mul.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_mul.rs

@@ -74,7 +74,7 @@
     crate_fn_ppc: mul::__mulkf3,
     sys_fn: __multf3,
     sys_fn_ppc: __mulkf3,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     asm: []
 }
 

diff --git a/library/compiler-builtins/builtins-test/benches/float_pow.rs b/library/compiler-builtins/builtins-test/benches/float_pow.rs
index 64e37dd..d749ae4 100644
--- a/library/compiler-builtins/builtins-test/benches/float_pow.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_pow.rs

@@ -24,7 +24,7 @@
 
 // FIXME(f16_f128): can be changed to only `f128_enabled` once `__multf3` and `__divtf3` are
 // distributed by nightly.
-#[cfg(all(f128_enabled, not(feature = "no-sys-f128")))]
+#[cfg(all(f128_enabled, not(no_sys_f128)))]
 float_bench! {
     name: powi_f128,
     sig: (a: f128, b: i32) -> f128,
@@ -32,7 +32,7 @@
     crate_fn_ppc: pow::__powikf2,
     sys_fn: __powitf2,
     sys_fn_ppc: __powikf2,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     asm: []
 }
 
@@ -42,7 +42,7 @@ pub fn float_pow() {
     powi_f32(&mut criterion);
     powi_f64(&mut criterion);
 
-    #[cfg(all(f128_enabled, not(feature = "no-sys-f128")))]
+    #[cfg(all(f128_enabled, not(no_sys_f128)))]
     powi_f128(&mut criterion);
 }
 

diff --git a/library/compiler-builtins/builtins-test/benches/float_sub.rs b/library/compiler-builtins/builtins-test/benches/float_sub.rs
index 8bae294..a8b73d7 100644
--- a/library/compiler-builtins/builtins-test/benches/float_sub.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_sub.rs

@@ -74,7 +74,7 @@
     crate_fn_ppc: sub::__subkf3,
     sys_fn: __subtf3,
     sys_fn_ppc: __subkf3,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     asm: []
 }
 

diff --git a/library/compiler-builtins/builtins-test/benches/float_trunc.rs b/library/compiler-builtins/builtins-test/benches/float_trunc.rs
index 9373f94..fdf96fd 100644
--- a/library/compiler-builtins/builtins-test/benches/float_trunc.rs
+++ b/library/compiler-builtins/builtins-test/benches/float_trunc.rs

@@ -11,7 +11,7 @@
     sig: (a: f32) -> f16,
     crate_fn: trunc::__truncsfhf2,
     sys_fn: __truncsfhf2,
-    sys_available: not(feature = "no-sys-f16"),
+    sys_available: not(no_sys_f16),
     asm: [
         #[cfg(target_arch = "aarch64")] {
             let ret: f16;
@@ -33,7 +33,7 @@
     sig: (a: f64) -> f16,
     crate_fn: trunc::__truncdfhf2,
     sys_fn: __truncdfhf2,
-    sys_available: not(feature = "no-sys-f16-f64-convert"),
+    sys_available: not(no_sys_f16_f64_convert),
     asm: [
         #[cfg(target_arch = "aarch64")] {
             let ret: f16;
@@ -90,7 +90,7 @@
     crate_fn_ppc: trunc::__trunckfhf2,
     sys_fn: __trunctfhf2,
     sys_fn_ppc: __trunckfhf2,
-    sys_available: not(feature = "no-sys-f16-f128-convert"),
+    sys_available: not(no_sys_f16_f128_convert),
     asm: [],
 }
 
@@ -102,7 +102,7 @@
     crate_fn_ppc: trunc::__trunckfsf2,
     sys_fn: __trunctfsf2,
     sys_fn_ppc: __trunckfsf2,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     asm: [],
 }
 
@@ -114,7 +114,7 @@
     crate_fn_ppc: trunc::__trunckfdf2,
     sys_fn: __trunctfdf2,
     sys_fn_ppc: __trunckfdf2,
-    sys_available: not(feature = "no-sys-f128"),
+    sys_available: not(no_sys_f128),
     asm: [],
 }
 

diff --git a/library/compiler-builtins/builtins-test/build.rs b/library/compiler-builtins/builtins-test/build.rs
index 5b2dcd1..f70dcec 100644
--- a/library/compiler-builtins/builtins-test/build.rs
+++ b/library/compiler-builtins/builtins-test/build.rs

@@ -6,7 +6,7 @@ mod builtins_configure {
 
 /// Features to enable
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
-enum Feature {
+enum SetCfg {
     NoSysF128,
     NoSysF128IntConvert,
     NoSysF16,
@@ -14,7 +14,15 @@ enum Feature {
     NoSysF16F128Convert,
 }
 
-impl Feature {
+impl SetCfg {
+    const ALL: &[Self] = &[
+        Self::NoSysF128,
+        Self::NoSysF128IntConvert,
+        Self::NoSysF16,
+        Self::NoSysF16F64Convert,
+        Self::NoSysF16F128Convert,
+    ];
+
     fn implies(self) -> &'static [Self] {
         match self {
             Self::NoSysF128 => [Self::NoSysF128IntConvert, Self::NoSysF16F128Convert].as_slice(),
@@ -24,13 +32,33 @@ fn implies(self) -> &'static [Self] {
             Self::NoSysF16F128Convert => [].as_slice(),
         }
     }
+
+    fn name(self) -> &'static str {
+        match self {
+            Self::NoSysF128 => "no_sys_f128",
+            Self::NoSysF128IntConvert => "no_sys_f128_int_convert",
+            Self::NoSysF16F64Convert => "no_sys_f16_f64_convert",
+            Self::NoSysF16F128Convert => "no_sys_f16_f128_convert",
+            Self::NoSysF16 => "no_sys_f16",
+        }
+    }
+
+    fn warning(self) -> &'static str {
+        match self {
+            SetCfg::NoSysF128 => "using apfloat fallback for f128",
+            SetCfg::NoSysF128IntConvert => "using apfloat fallback for f128 <-> int conversions",
+            SetCfg::NoSysF16F64Convert => "using apfloat fallback for f16 <-> f64 conversions",
+            SetCfg::NoSysF16F128Convert => "using apfloat fallback for f16 <-> f128 conversions",
+            SetCfg::NoSysF16 => "using apfloat fallback for f16",
+        }
+    }
 }
 
 fn main() {
     println!("cargo::rerun-if-changed=../configure.rs");
 
     let target = builtins_configure::Target::from_env();
-    let mut features = HashSet::new();
+    let mut to_set = HashSet::new();
 
     // These platforms do not have f128 symbols available in their system libraries, so
     // skip related tests.
@@ -51,14 +79,14 @@ fn main() {
         // <https://github.com/rust-lang/compiler-builtins/pull/606#issuecomment-2105657287>.
         || target.arch == "powerpc64"
     {
-        features.insert(Feature::NoSysF128);
+        to_set.insert(SetCfg::NoSysF128);
     }
 
     if target.arch == "x86" {
         // 32-bit x86 does not have `__fixunstfti`/`__fixtfti` but does have everything else
-        features.insert(Feature::NoSysF128IntConvert);
+        to_set.insert(SetCfg::NoSysF128IntConvert);
         // FIXME: 32-bit x86 has a bug in `f128 -> f16` system libraries
-        features.insert(Feature::NoSysF16F128Convert);
+        to_set.insert(SetCfg::NoSysF16F128Convert);
     }
 
     // These platforms do not have f16 symbols available in their system libraries, so
@@ -77,42 +105,30 @@ fn main() {
         || target.arch == "wasm32"
         || target.arch == "wasm64"
     {
-        features.insert(Feature::NoSysF16);
+        to_set.insert(SetCfg::NoSysF16);
     }
 
     // These platforms are missing either `__extendhfdf2` or `__truncdfhf2`.
     if target.vendor == "apple" || target.os == "windows" {
-        features.insert(Feature::NoSysF16F64Convert);
+        to_set.insert(SetCfg::NoSysF16F64Convert);
     }
 
     // Add implied features. Collection is required for borrows.
-    features.extend(
-        features
+    to_set.extend(
+        to_set
             .iter()
             .flat_map(|x| x.implies())
             .copied()
             .collect::<Vec<_>>(),
     );
 
-    for feature in features {
-        let (name, warning) = match feature {
-            Feature::NoSysF128 => ("no-sys-f128", "using apfloat fallback for f128"),
-            Feature::NoSysF128IntConvert => (
-                "no-sys-f128-int-convert",
-                "using apfloat fallback for f128 <-> int conversions",
-            ),
-            Feature::NoSysF16F64Convert => (
-                "no-sys-f16-f64-convert",
-                "using apfloat fallback for f16 <-> f64 conversions",
-            ),
-            Feature::NoSysF16F128Convert => (
-                "no-sys-f16-f128-convert",
-                "using apfloat fallback for f16 <-> f128 conversions",
-            ),
-            Feature::NoSysF16 => ("no-sys-f16", "using apfloat fallback for f16"),
-        };
-        println!("cargo:warning={warning}");
-        println!("cargo:rustc-cfg=feature=\"{name}\"");
+    for cfg in SetCfg::ALL {
+        println!("cargo:rustc-check-cfg=cfg({})", cfg.name());
+    }
+
+    for cfg in to_set {
+        println!("cargo:warning={}", cfg.warning());
+        println!("cargo:rustc-cfg={}", cfg.name());
     }
 
     builtins_configure::configure_aliases(&target);

diff --git a/library/compiler-builtins/builtins-test/tests/addsub.rs b/library/compiler-builtins/builtins-test/tests/addsub.rs
index de1235b..859de3e 100644
--- a/library/compiler-builtins/builtins-test/tests/addsub.rs
+++ b/library/compiler-builtins/builtins-test/tests/addsub.rs

@@ -131,12 +131,12 @@ mod float_addsub {
     #[cfg(not(x86_no_sse2))]
     #[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc64")))]
     float_sum! {
-        f128, __addtf3, __subtf3, Quad, not(feature = "no-sys-f128");
+        f128, __addtf3, __subtf3, Quad, not(no_sys_f128);
     }
 
     #[cfg(f128_enabled)]
     #[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
     float_sum! {
-        f128, __addkf3, __subkf3, Quad, not(feature = "no-sys-f128");
+        f128, __addkf3, __subkf3, Quad, not(no_sys_f128);
     }
 }

diff --git a/library/compiler-builtins/builtins-test/tests/cmp.rs b/library/compiler-builtins/builtins-test/tests/cmp.rs
index 4b01b6c..d936002 100644
--- a/library/compiler-builtins/builtins-test/tests/cmp.rs
+++ b/library/compiler-builtins/builtins-test/tests/cmp.rs

@@ -125,19 +125,19 @@ fn cmp_f128() {
 
         fuzz_float_2(N, |x: f128, y: f128| {
             let x_is_nan = apfloat_fallback!(
-                f128, Quad, not(feature = "no-sys-f128"),
+                f128, Quad, not(no_sys_f128),
                 |x: FloatTy| x.is_nan() => no_convert,
                 x
             );
             let y_is_nan = apfloat_fallback!(
-                f128, Quad, not(feature = "no-sys-f128"),
+                f128, Quad, not(no_sys_f128),
                 |x: FloatTy| x.is_nan() => no_convert,
                 y
             );
 
             assert_eq!(__unordtf2(x, y) != 0, x_is_nan || y_is_nan);
 
-            cmp!(f128, x, y, Quad, not(feature = "no-sys-f128"),
+            cmp!(f128, x, y, Quad, not(no_sys_f128),
                 1, __lttf2;
                 1, __letf2;
                 1, __eqtf2;

diff --git a/library/compiler-builtins/builtins-test/tests/conv.rs b/library/compiler-builtins/builtins-test/tests/conv.rs
index 9d8dde5..e01eb25 100644
--- a/library/compiler-builtins/builtins-test/tests/conv.rs
+++ b/library/compiler-builtins/builtins-test/tests/conv.rs

@@ -117,7 +117,7 @@ fn $fn() {
 
     #[cfg(f128_enabled)]
     #[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc64")))]
-    i_to_f! { f128, Quad, not(feature = "no-sys-f128-int-convert"),
+    i_to_f! { f128, Quad, not(no_sys_f128_int_convert),
         u32, __floatunsitf;
         i32, __floatsitf;
         u64, __floatunditf;
@@ -128,7 +128,7 @@ fn $fn() {
 
     #[cfg(f128_enabled)]
     #[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
-    i_to_f! { f128, Quad, not(feature = "no-sys-f128-int-convert"),
+    i_to_f! { f128, Quad, not(no_sys_f128_int_convert),
         u32, __floatunsikf;
         i32, __floatsikf;
         u64, __floatundikf;
@@ -236,7 +236,7 @@ fn f128_to_int() {
                 x,
                 f128,
                 Quad,
-                not(feature = "no-sys-f128-int-convert"),
+                not(no_sys_f128_int_convert),
                 u32, __fixunstfsi;
                 u64, __fixunstfdi;
                 u128, __fixunstfti;
@@ -309,12 +309,12 @@ mod extend {
     )))]
     f_to_f! {
         extend,
-        f16 => f32, Half => Single, __extendhfsf2, not(feature = "no-sys-f16");
-        f16 => f32, Half => Single, __gnu_h2f_ieee, not(feature = "no-sys-f16");
-        f16 => f64, Half => Double, __extendhfdf2, not(feature = "no-sys-f16-f64-convert");
-        f16 => f128, Half => Quad, __extendhftf2, not(feature = "no-sys-f16-f128-convert");
-        f32 => f128, Single => Quad, __extendsftf2, not(feature = "no-sys-f128");
-        f64 => f128, Double => Quad, __extenddftf2, not(feature = "no-sys-f128");
+        f16 => f32, Half => Single, __extendhfsf2, not(no_sys_f16);
+        f16 => f32, Half => Single, __gnu_h2f_ieee, not(no_sys_f16);
+        f16 => f64, Half => Double, __extendhfdf2, not(no_sys_f16_f64_convert);
+        f16 => f128, Half => Quad, __extendhftf2, not(no_sys_f16_f128_convert);
+        f32 => f128, Single => Quad, __extendsftf2, not(no_sys_f128);
+        f64 => f128, Double => Quad, __extenddftf2, not(no_sys_f128);
     }
 
     #[cfg(f128_enabled)]
@@ -322,8 +322,8 @@ mod extend {
     f_to_f! {
         extend,
         // FIXME(#655): `f16` tests disabled until we can bootstrap symbols
-        f32 => f128, Single => Quad, __extendsfkf2, not(feature = "no-sys-f128");
-        f64 => f128, Double => Quad, __extenddfkf2, not(feature = "no-sys-f128");
+        f32 => f128, Single => Quad, __extendsfkf2, not(no_sys_f128);
+        f64 => f128, Double => Quad, __extenddfkf2, not(no_sys_f128);
     }
 }
 
@@ -343,12 +343,12 @@ mod trunc {
     )))]
     f_to_f! {
         trunc,
-        f32 => f16, Single => Half, __truncsfhf2, not(feature = "no-sys-f16");
-        f32 => f16, Single => Half, __gnu_f2h_ieee, not(feature = "no-sys-f16");
-        f64 => f16, Double => Half, __truncdfhf2, not(feature = "no-sys-f16-f64-convert");
-        f128 => f16, Quad => Half, __trunctfhf2, not(feature = "no-sys-f16-f128-convert");
-        f128 => f32, Quad => Single, __trunctfsf2, not(feature = "no-sys-f128");
-        f128 => f64, Quad => Double, __trunctfdf2, not(feature = "no-sys-f128");
+        f32 => f16, Single => Half, __truncsfhf2, not(no_sys_f16);
+        f32 => f16, Single => Half, __gnu_f2h_ieee, not(no_sys_f16);
+        f64 => f16, Double => Half, __truncdfhf2, not(no_sys_f16_f64_convert);
+        f128 => f16, Quad => Half, __trunctfhf2, not(no_sys_f16_f128_convert);
+        f128 => f32, Quad => Single, __trunctfsf2, not(no_sys_f128);
+        f128 => f64, Quad => Double, __trunctfdf2, not(no_sys_f128);
     }
 
     #[cfg(f128_enabled)]
@@ -356,7 +356,7 @@ mod trunc {
     f_to_f! {
         trunc,
         // FIXME(#655): `f16` tests disabled until we can bootstrap symbols
-        f128 => f32, Quad => Single, __trunckfsf2, not(feature = "no-sys-f128");
-        f128 => f64, Quad => Double, __trunckfdf2, not(feature = "no-sys-f128");
+        f128 => f32, Quad => Single, __trunckfsf2, not(no_sys_f128);
+        f128 => f64, Quad => Double, __trunckfdf2, not(no_sys_f128);
     }
 }

diff --git a/library/compiler-builtins/builtins-test/tests/div_rem.rs b/library/compiler-builtins/builtins-test/tests/div_rem.rs
index fccd4218..5d04fe9 100644
--- a/library/compiler-builtins/builtins-test/tests/div_rem.rs
+++ b/library/compiler-builtins/builtins-test/tests/div_rem.rs

@@ -154,12 +154,12 @@ mod float_div {
         f128, __divtf3, Quad,
         // FIXME(llvm): there is a bug in LLVM rt.
         // See <https://github.com/llvm/llvm-project/issues/91840>.
-        not(any(feature = "no-sys-f128", all(target_arch = "aarch64", target_os = "linux")));
+        not(any(no_sys_f128, all(target_arch = "aarch64", target_os = "linux")));
     }
 
     #[cfg(f128_enabled)]
     #[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
     float! {
-        f128, __divkf3, Quad, not(feature = "no-sys-f128");
+        f128, __divkf3, Quad, not(no_sys_f128);
     }
 }

diff --git a/library/compiler-builtins/builtins-test/tests/float_pow.rs b/library/compiler-builtins/builtins-test/tests/float_pow.rs
index 750869d..c808b9e 100644
--- a/library/compiler-builtins/builtins-test/tests/float_pow.rs
+++ b/library/compiler-builtins/builtins-test/tests/float_pow.rs

@@ -62,11 +62,11 @@ fn $fn() {
 #[cfg(f128_enabled)]
 #[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc64")))]
 pow! {
-    f128, 1e-36, __powitf2, not(feature = "no-sys-f128");
+    f128, 1e-36, __powitf2, not(no_sys_f128);
 }
 
 #[cfg(f128_enabled)]
 #[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
 pow! {
-    f128, 1e-36, __powikf2, not(feature = "no-sys-f128");
+    f128, 1e-36, __powikf2, not(no_sys_f128);
 }

diff --git a/library/compiler-builtins/builtins-test/tests/mul.rs b/library/compiler-builtins/builtins-test/tests/mul.rs
index 7c3bffe..b16d729 100644
--- a/library/compiler-builtins/builtins-test/tests/mul.rs
+++ b/library/compiler-builtins/builtins-test/tests/mul.rs

@@ -142,7 +142,7 @@ mod float_mul_f128 {
         f128, __multf3, Quad,
         // FIXME(llvm): there is a bug in LLVM rt.
         // See <https://github.com/llvm/llvm-project/issues/91840>.
-        not(any(feature = "no-sys-f128", all(target_arch = "aarch64", target_os = "linux")));
+        not(any(no_sys_f128, all(target_arch = "aarch64", target_os = "linux")));
     }
 }
 
@@ -152,6 +152,6 @@ mod float_mul_f128_ppc {
     use super::*;
 
     float_mul! {
-        f128, __mulkf3, Quad, not(feature = "no-sys-f128");
+        f128, __mulkf3, Quad, not(no_sys_f128);
     }
 }