[libc][math] Update test/src/math/smoke/FmaTest.h to not rely on compiler runtime. (#159503)

Author: lntue

libc/test/src/math/smoke/FmaTest.h

@@ -86,9 +86,8 @@ class FmaTestTemplate : public LIBC_NAMESPACE::testing::FEnvSafeTest {
     }
 
     // Test overflow.
-    OutType z = out.max_normal;
     InType in_z = LIBC_NAMESPACE::fputil::cast<InType>(out.max_normal);
-    EXPECT_FP_EQ_ALL_ROUNDING(OutType(0.75) * z,
+    EXPECT_FP_EQ_ALL_ROUNDING(func(InType(-0.25), in_z, in_z),
                               func(InType(1.75), in_z, -in_z));
 
     // Exact cancellation.

utils/bazel/llvm-project-overlay/libc/test/src/math/smoke/BUILD.bazel

@@ -204,21 +204,20 @@ math_test(
     hdrs = ["FmaTest.h"],
 )
 
-# TODO: Reenable these tests once they pass at Google.
-# math_test(
-#     name = "f16fma",
-#     hdrs = ["FmaTest.h"],
-# )
-#
-# math_test(
-#     name = "f16fmaf",
-#     hdrs = ["FmaTest.h"],
-# )
-#
-# math_test(
-#     name = "f16fmal",
-#     hdrs = ["FmaTest.h"],
-# )
+math_test(
+    name = "f16fma",
+    hdrs = ["FmaTest.h"],
+)
+
+math_test(
+    name = "f16fmaf",
+    hdrs = ["FmaTest.h"],
+)
+
+math_test(
+    name = "f16fmal",
+    hdrs = ["FmaTest.h"],
+)
 
 math_test(
     name = "dmull",
@@ -485,11 +484,10 @@ math_test(
     hdrs = ["FmaTest.h"],
 )
 
-# TODO: Reenable this test once it passes at Google.
-# math_test(
-#     name = "fmaf16",
-#     hdrs = ["FmaTest.h"],
-# )
+math_test(
+    name = "fmaf16",
+    hdrs = ["FmaTest.h"],
+)
 
 math_test(
     name = "fmax",