cmd/compile: fix typo in floating point rule

Change-Id: Idfb64fcb26f48d5b70bab872f9a3d96a036be681
Reviewed-on: https://go-review.googlesource.com/63950
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -197,6 +197,16 @@ func cvt12(a float32) uint {
 	return uint(a)
 }
 
+//go:noinline
+func f2i64p(v float64) *int64 {
+	return ip64(int64(v / 0.1))
+}
+
+//go:noinline
+func ip64(v int64) *int64 {
+	return &v
+}
+
 func TestFloatConvert(t *testing.T) {
 	if got := cvt1(3.5); got != 3 {
 		t.Errorf("cvt1 got %d, wanted 3", got)
@@ -234,6 +244,9 @@ func TestFloatConvert(t *testing.T) {
 	if got := cvt12(3.5); got != 3 {
 		t.Errorf("cvt12 got %d, wanted 3", got)
 	}
+	if got := *f2i64p(10); got != 100 {
+		t.Errorf("f2i64p got %d, wanted 100", got)
+	}
 }
 
 var sinkFloat float64

src/cmd/compile/internal/ssa/gen/generic.rules

@@ -53,7 +53,7 @@
 (Cvt32Fto32  (Const32F [c])) -> (Const32  [int64(int32(i2f(c)))])
 (Cvt32Fto64  (Const32F [c])) -> (Const64  [int64(i2f(c))])
 (Cvt64Fto32  (Const64F [c])) -> (Const32  [int64(int32(i2f(c)))])
-(Cvt64Fto64  (Const64F [c])) -> (Const32  [int64(i2f(c))])
+(Cvt64Fto64  (Const64F [c])) -> (Const64  [int64(i2f(c))])
 (Round32F x:(Const32F)) -> x
 (Round64F x:(Const64F)) -> x
 

src/cmd/compile/internal/ssa/rewritegeneric.go

@@ -7194,14 +7194,14 @@ func rewriteValuegeneric_OpCvt64Fto32F_0(v *Value) bool {
 func rewriteValuegeneric_OpCvt64Fto64_0(v *Value) bool {
 	// match: (Cvt64Fto64 (Const64F [c]))
 	// cond:
-	// result: (Const32  [int64(i2f(c))])
+	// result: (Const64  [int64(i2f(c))])
 	for {
 		v_0 := v.Args[0]
 		if v_0.Op != OpConst64F {
 			break
 		}
 		c := v_0.AuxInt
-		v.reset(OpConst32)
+		v.reset(OpConst64)
 		v.AuxInt = int64(i2f(c))
 		return true
 	}