From 2c7495c41bfd5fd2245823f870a2cd97fcfd7f0e Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Fri, 7 Feb 2025 05:22:07 +0000
Subject: [PATCH 1/3] Add a way to avoid `f32` implementations that do math as
 an `f64`

---
 ci/run.sh                |  3 +++
 configure.rs             | 10 ++++++++++
 etc/has-nowiden-impl.txt |  2 ++
 src/math/fmaf.rs         |  6 +++++-
 src/math/generic/fma.rs  | 10 ++++++++++
 5 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 etc/has-nowiden-impl.txt

diff --git a/ci/run.sh b/ci/run.sh
index a946d325e..dcbd0bac4 100755
--- a/ci/run.sh
+++ b/ci/run.sh
@@ -14,6 +14,8 @@ if [ -z "$target" ]; then
     target="$host_target"
 fi
 
+nowiden_tests=$($cmd "$profile" release-checked --features force-soft-floats)
+
 # We enumerate features manually.
 flags="$flags --no-default-features"
 
@@ -112,6 +114,7 @@ $cmd --features unstable-intrinsics --benches
 # Test the same in release mode, which also increases coverage. Also ensure
 # the soft float routines are checked.
 $cmd "$profile" release-checked
+LIBM_F32_NO_WIDEN=1 $cmd "$profile" release-checked -- $nowiden_tests
 $cmd "$profile" release-checked --features force-soft-floats
 $cmd "$profile" release-checked --features unstable-intrinsics
 $cmd "$profile" release-checked --features unstable-intrinsics --benches
diff --git a/configure.rs b/configure.rs
index 8b8ba9815..e696492cf 100644
--- a/configure.rs
+++ b/configure.rs
@@ -50,6 +50,7 @@ pub fn emit_libm_config(cfg: &Config) {
     emit_intrinsics_cfg();
     emit_arch_cfg();
     emit_optimization_cfg(cfg);
+    emit_widen_cfg(cfg);
     emit_cfg_shorthands(cfg);
     emit_cfg_env(cfg);
     emit_f16_f128_cfg(cfg);
@@ -96,6 +97,15 @@ fn emit_optimization_cfg(cfg: &Config) {
     }
 }
 
+fn emit_widen_cfg(_cfg: &Config) {
+    println!("cargo:rustc-check-cfg=cfg(f32_no_widen)");
+    println!("cargo:rerun-if-env-changed=LIBM_F32_NO_WIDEN");
+
+    if env::var_os("LIBM_F32_NO_WIDEN").is_some() {
+        println!("cargo:rustc-cfg=f32_no_widen");
+    }
+}
+
 /// Provide an alias for common longer config combinations.
 fn emit_cfg_shorthands(cfg: &Config) {
     println!("cargo:rustc-check-cfg=cfg(x86_no_sse)");
diff --git a/etc/has-nowiden-impl.txt b/etc/has-nowiden-impl.txt
new file mode 100644
index 000000000..4b61bec79
--- /dev/null
+++ b/etc/has-nowiden-impl.txt
@@ -0,0 +1,2 @@
+# Functions that have a different version based on f32_no_widen
+fmaf
diff --git a/src/math/fmaf.rs b/src/math/fmaf.rs
index 40d7f40d6..0fcc96b93 100644
--- a/src/math/fmaf.rs
+++ b/src/math/fmaf.rs
@@ -5,7 +5,11 @@
 /// according to the rounding mode characterized by the value of FLT_ROUNDS.
 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
 pub fn fmaf(x: f32, y: f32, z: f32) -> f32 {
-    super::generic::fma_wide(x, y, z)
+    if cfg!(f32_no_widen) {
+        super::generic::fma(x, y, z)
+    } else {
+        super::generic::fma_wide(x, y, z)
+    }
 }
 
 #[cfg(test)]
diff --git a/src/math/generic/fma.rs b/src/math/generic/fma.rs
index a40d7aaaf..719154553 100644
--- a/src/math/generic/fma.rs
+++ b/src/math/generic/fma.rs
@@ -345,6 +345,16 @@ pub trait FmaHelper {
     fn raise_underflow_ret_zero(self) -> Self;
 }
 
+impl FmaHelper for f32 {
+    fn raise_underflow_as_min_positive(self) -> Self {
+        f32::MIN_POSITIVE.copysign(self)
+    }
+
+    fn raise_underflow_ret_zero(self) -> Self {
+        f32::ZERO
+    }
+}
+
 impl FmaHelper for f64 {
     fn raise_underflow_as_min_positive(self) -> Self {
         /* min normal after rounding, underflow depends

From 888e51c7f407247f88c8dd27a4d1f7d9a71e7965 Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Fri, 7 Feb 2025 05:24:21 +0000
Subject: [PATCH 2/3] sh update

---
 ci/run.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ci/run.sh b/ci/run.sh
index dcbd0bac4..b42959af4 100755
--- a/ci/run.sh
+++ b/ci/run.sh
@@ -114,7 +114,7 @@ $cmd --features unstable-intrinsics --benches
 # Test the same in release mode, which also increases coverage. Also ensure
 # the soft float routines are checked.
 $cmd "$profile" release-checked
-LIBM_F32_NO_WIDEN=1 $cmd "$profile" release-checked -- $nowiden_tests
+[ -n "${nowiden_tests:-}" ] && LIBM_F32_NO_WIDEN=1 $cmd "$profile" release-checked -- $nowiden_tests
 $cmd "$profile" release-checked --features force-soft-floats
 $cmd "$profile" release-checked --features unstable-intrinsics
 $cmd "$profile" release-checked --features unstable-intrinsics --benches

From 98c6fa65ed5033d171853c96b29a71260fdde6e8 Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Fri, 7 Feb 2025 05:38:42 +0000
Subject: [PATCH 3/3] sh update

---
 ci/run.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ci/run.sh b/ci/run.sh
index b42959af4..739a644dd 100755
--- a/ci/run.sh
+++ b/ci/run.sh
@@ -14,7 +14,7 @@ if [ -z "$target" ]; then
     target="$host_target"
 fi
 
-nowiden_tests=$($cmd "$profile" release-checked --features force-soft-floats)
+nowiden_tests=$(grep -vE '^#' etc/has-nowiden-impl.txt | tr '\n' ' ')
 
 # We enumerate features manually.
 flags="$flags --no-default-features"