Change float to integer tests to have an apfloat fallback

Author: tgross35

testcrate/tests/conv.rs

@@ -96,14 +96,41 @@ fn int_to_float() {
 }
 
 macro_rules! f_to_i {
-    ($x:ident, $($f:ty, $fn:ident);*;) => {
+    ($x:ident, $f_ty:ty, $apfloat_ty:ident, $sys_available:meta, $($i_ty:ty, $fn:ident);*;) => {
         $(
             // it is undefined behavior in the first place to do conversions with NaNs
-            if !$x.is_nan() {
-                let conv0 = $x as $f;
-                let conv1: $f = $fn($x);
+            if !apfloat_fallback!(
+                $f_ty, $apfloat_ty, $sys_available, |x: FloatTy| x.is_nan() => no_convert, $x
+            ) {
+                let conv0 = apfloat_fallback!(
+                    $f_ty, $apfloat_ty, $sys_available,
+                    // Use an `as` cast when the builtin is available on the system.
+                    |x| x as $i_ty;
+                    // When the builtin is not available, we need to use a different conversion
+                    // method (since apfloat doesn't support `as` casting).
+                    |x: $f_ty| {
+                        use compiler_builtins::int::MinInt;
+
+                        let apf = FloatTy::from_bits(x.to_bits().into());
+                        let bits: usize = <$i_ty>::BITS.try_into().unwrap();
+
+                        let err_fn = || panic!(
+                            "Unable to convert value {x:?} to type {}:", stringify!($i_ty)
+                        );
+
+                        if <$i_ty>::SIGNED {
+                           <$i_ty>::try_from(apf.to_i128(bits).value).ok().unwrap_or_else(err_fn)
+                        } else {
+                           <$i_ty>::try_from(apf.to_u128(bits).value).ok().unwrap_or_else(err_fn)
+                        }
+                    },
+                    $x
+                );
+
+                // $x as $i_ty;
+                let conv1: $i_ty = $fn($x);
                 if conv0 != conv1 {
-                    panic!("{}({}): std: {}, builtins: {}", stringify!($fn), $x, conv0, conv1);
+                    panic!("{}({:?}): std: {:?}, builtins: {:?}", stringify!($fn), $x, conv0, conv1);
                 }
             }
         )*
@@ -120,7 +147,7 @@ fn float_to_int() {
     };
 
     fuzz_float(N, |x: f32| {
-        f_to_i!(x,
+        f_to_i!(x, f32, Single, all(),
             u32, __fixunssfsi;
             u64, __fixunssfdi;
             u128, __fixunssfti;
@@ -130,7 +157,7 @@ fn float_to_int() {
         );
     });
     fuzz_float(N, |x: f64| {
-        f_to_i!(x,
+        f_to_i!(x, f64, Double, all(),
             u32, __fixunsdfsi;
             u64, __fixunsdfdi;
             u128, __fixunsdfti;