ssa: fix bitcast for float32

cl/_testrt/float2any/in.go

@@ -0,0 +1,28 @@
+package main
+
+const pi = 3.14159265
+
+func check32(v any) {
+	if v.(float32) != pi {
+		panic("error f32")
+	}
+}
+
+func check64(v any) {
+	if v.(float64) != pi {
+		panic("error f64")
+	}
+}
+
+func f32() float32 {
+	return pi
+}
+
+func f64() float64 {
+	return pi
+}
+
+func main() {
+	check32(f32())
+	check64(f64())
+}