cmd/compile: don't fold >32bit constants into a MULQ

Don't fold constant factors into a multiply
beyond the capacity of a MULQ instruction (32 bits).

Fixes #16733

Change-Id: Idc213c6cb06f7c94008a8cf9e60a9e77d085fd89
Reviewed-on: https://go-review.googlesource.com/27160
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/ssa/gen/AMD64.rules

@@ -522,7 +522,7 @@
 (XORQconst [c] (XORQconst [d] x)) -> (XORQconst [c ^ d] x)
 
 (MULLconst [c] (MULLconst [d] x)) -> (MULLconst [int64(int32(c * d))] x)
-(MULQconst [c] (MULQconst [d] x)) -> (MULQconst [c * d] x)
+(MULQconst [c] (MULQconst [d] x)) && is32Bit(c*d) -> (MULQconst [c * d] x)
 
 (ORQ x (MOVQconst [c])) && is32Bit(c) -> (ORQconst [c] x)
 (ORQ (MOVQconst [c]) x) && is32Bit(c) -> (ORQconst [c] x)

src/cmd/compile/internal/ssa/rewriteAMD64.go

@@ -9753,7 +9753,7 @@ func rewriteValueAMD64_OpAMD64MULQconst(v *Value, config *Config) bool {
 	b := v.Block
 	_ = b
 	// match: (MULQconst [c] (MULQconst [d] x))
-	// cond:
+	// cond: is32Bit(c*d)
 	// result: (MULQconst [c * d] x)
 	for {
 		c := v.AuxInt
@@ -9763,6 +9763,9 @@ func rewriteValueAMD64_OpAMD64MULQconst(v *Value, config *Config) bool {
 		}
 		d := v_0.AuxInt
 		x := v_0.Args[0]
+		if !(is32Bit(c * d)) {
+			break
+		}
 		v.reset(OpAMD64MULQconst)
 		v.AuxInt = c * d
 		v.AddArg(x)

test/fixedbugs/issue16733.go

+// compile
+
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 16733: don't fold constant factors into a multiply
+// beyond the capacity of a MULQ instruction (32 bits).
+
+package p
+
+func f(n int64) int64 {
+	n *= 1000000
+	n *= 1000000
+	return n
+}