cmd/compile/internal/gc: skip TestFP on mips64x

The legacy mips64 backend doesn't handle large uint->float conversion
correctly. See #15552.

Change-Id: I84ceeaa95cc4e85f09cc46dfb30ab5d151f6b205
Reviewed-on: https://go-review.googlesource.com/22800Reviewed-by: Minux Ma <minux@golang.org>

src/cmd/compile/internal/gc/ssa_test.go

@@ -57,7 +57,12 @@ func TestArithmetic(t *testing.T) {
 }
 
 // TestFP tests that both backends have the same result for floating point expressions.
-func TestFP(t *testing.T) { runTest(t, "fp_ssa.go") }
+func TestFP(t *testing.T) {
+	if runtime.GOARCH == "mips64" || runtime.GOARCH == "mips64le" {
+		t.Skip("legacy mips64 compiler doesn't handle uint->float conversion correctly (issue 15552)")
+	}
+	runTest(t, "fp_ssa.go")
+}
 
 // TestArithmeticBoundary tests boundary results for arithmetic operations.
 func TestArithmeticBoundary(t *testing.T) { runTest(t, "arithBoundary_ssa.go") }