mantissa <<= shift
		exp = 1 - int32(shift)
	} else {
		// Add implicit 1 bit
		mantissa |= 1 << 52
	}
	return
}

// FMA returns x * y + z, computed with only one rounding.
// (That is, FMA returns the fused multiply-add of x, y, and z.)
func FMA(x, y, z float64) float64 {
	bx, by, bz := Float64bits(x), Float64bits(y), Float64bits(z)

	// Inf or NaN or zero involved. At most one rounding will occur.

David Chase <******@****.***> 1667836928 -0500

	}

	testenv.MustHaveGoBuild(t)
	gocmd := testenv.GoToolPath(t)
	tmpdir := t.TempDir()
	source := filepath.Join("testdata", "fma.go")
	output := filepath.Join(tmpdir, "fma.exe")
	cmd := testenv.Command(t, gocmd, "build", "-o", output, source)
	// The hash-dependence on file path name is dodged by specifying "all hashes ending in 1" plus "all hashes ending in 0"

		fastlog2Table[i] = log2(1.0 + float64(i)/(1<<fastlogNumBits))
	}
	return fastlog2Table
}

// log2 is a local copy of math.Log2 with an explicit float64 conversion
// to disable FMA. This lets us generate the same output on all platforms.
func log2(x float64) float64 {
	frac, exp := math.Frexp(x)
	// Make sure exact powers of two give an exact answer.

	sink64[3] = math.Copysign(-1, c)
}

func fma(x, y, z float64) float64 {
	// amd64/v3:-".*x86HasFMA"
	// amd64:"VFMADD231SD"
	// arm/6:"FMULAD"
	// arm64:"FMADDD"
	// s390x:"FMADD"
	// ppc64x:"FMADD"
	// riscv64:"FMADDD"
	return math.FMA(x, y, z)
}

func fms(x, y, z float64) float64 {
	// riscv64:"FMSUBD"
	return math.FMA(x, y, -z)
}

func fnms(x, y, z float64) float64 {

		}
	}
}

func TestFMA(t *testing.T) {
	for _, tt := range []struct {
		x, y, z, want float64
	}{
		{2, 3, 4, 10},
		{3, 4, 5, 17},
	} {
		if got := math.FMA(tt.x, tt.y, tt.z); got != tt.want {
			t.Errorf("FMA(%f,%f,%f) = %f, want %f", tt.x, tt.y, tt.z, got, tt.want)
		}
	}

			option{Name: "avx", Feature: &X86.HasAVX},
			option{Name: "avx2", Feature: &X86.HasAVX2},
			option{Name: "bmi1", Feature: &X86.HasBMI1},
			option{Name: "bmi2", Feature: &X86.HasBMI2},
			option{Name: "fma", Feature: &X86.HasFMA})
	}
	if level < 4 {
		// These options are required at level 4. At lower levels
		// they can be turned off.
		options = append(options,
			option{Name: "avx512f", Feature: &X86.HasAVX512F},

		{Name: "amxbf16", Feature: &X86.HasAMXBF16},
		{Name: "bmi1", Feature: &X86.HasBMI1},
		{Name: "bmi2", Feature: &X86.HasBMI2},
		{Name: "cx16", Feature: &X86.HasCX16},
		{Name: "erms", Feature: &X86.HasERMS},
		{Name: "fma", Feature: &X86.HasFMA},
		{Name: "osxsave", Feature: &X86.HasOSXSAVE},
		{Name: "pclmulqdq", Feature: &X86.HasPCLMULQDQ},
		{Name: "popcnt", Feature: &X86.HasPOPCNT},
		{Name: "rdrand", Feature: &X86.HasRDRAND},

	SoftFloat      bool        //
	Race           bool        // race detector enabled
	BigEndian      bool        //
	UseFMA         bool        // Use hardware FMA operation
	unalignedOK    bool        // Unaligned loads/stores are ok
	haveBswap64    bool        // architecture implements Bswap64
	haveBswap32    bool        // architecture implements Bswap32

		t.Errorf("Yn(0, 0) = %g, want %g", f, Inf(-1))
	}
}

var PortableFMA = FMA // hide call from compiler intrinsic; falls back to portable code

func TestFMA(t *testing.T) {
	for _, c := range fmaC {
		got := FMA(c.x, c.y, c.z)
		if !alike(got, c.want) {
			t.Errorf("FMA(%g,%g,%g) == %g; want %g", c.x, c.y, c.z, got, c.want)
		}
		got = PortableFMA(c.x, c.y, c.z)