cmd/compile: prevent constant folding of +/- when result is NaN

Missed as part of CL 221790. It isn't just * and / that can make NaNs.

Update #36400
Fixes #38359

Change-Id: I3fa562f772fe03b510793a6dc0cf6189c0c3e652
Reviewed-on: https://go-review.googlesource.com/c/go/+/227860
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alberto Donizetti <alb.donizetti@gmail.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

diff --git a/src/cmd/compile/internal/ssa/gen/generic.rules b/src/cmd/compile/internal/ssa/gen/generic.rules
index 7ae34cec565268a63042dfb0f4bd8f4b95f9ffd2..28e45376df2259d64d6925369f04e7301590faaf 100644 (file)
--- a/src/cmd/compile/internal/ssa/gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/gen/generic.rules
@@ -103,8 +103,8 @@
 (Add16  (Const16 [c])  (Const16 [d]))  -> (Const16 [int64(int16(c+d))])
 (Add32  (Const32 [c])  (Const32 [d]))  -> (Const32 [int64(int32(c+d))])
 (Add64  (Const64 [c])  (Const64 [d]))  -> (Const64 [c+d])
-(Add32F (Const32F [c]) (Const32F [d])) -> (Const32F [auxFrom32F(auxTo32F(c) + auxTo32F(d))])
-(Add64F (Const64F [c]) (Const64F [d])) -> (Const64F [auxFrom64F(auxTo64F(c) + auxTo64F(d))])
+(Add32F (Const32F [c]) (Const32F [d])) && !math.IsNaN(float64(auxTo32F(c) + auxTo32F(d))) -> (Const32F [auxFrom32F(auxTo32F(c) + auxTo32F(d))])
+(Add64F (Const64F [c]) (Const64F [d])) && !math.IsNaN(auxTo64F(c) + auxTo64F(d)) -> (Const64F [auxFrom64F(auxTo64F(c) + auxTo64F(d))])
 (AddPtr <t> x (Const64 [c])) -> (OffPtr <t> x [c])
 (AddPtr <t> x (Const32 [c])) -> (OffPtr <t> x [c])
 
@@ -112,8 +112,8 @@
 (Sub16  (Const16 [c]) (Const16 [d]))   -> (Const16 [int64(int16(c-d))])
 (Sub32  (Const32 [c]) (Const32 [d]))   -> (Const32 [int64(int32(c-d))])
 (Sub64  (Const64 [c]) (Const64 [d]))   -> (Const64 [c-d])
-(Sub32F (Const32F [c]) (Const32F [d])) -> (Const32F [auxFrom32F(auxTo32F(c) - auxTo32F(d))])
-(Sub64F (Const64F [c]) (Const64F [d])) -> (Const64F [auxFrom64F(auxTo64F(c) - auxTo64F(d))])
+(Sub32F (Const32F [c]) (Const32F [d])) && !math.IsNaN(float64(auxTo32F(c) - auxTo32F(d))) -> (Const32F [auxFrom32F(auxTo32F(c) - auxTo32F(d))])
+(Sub64F (Const64F [c]) (Const64F [d])) && !math.IsNaN(auxTo64F(c) - auxTo64F(d)) -> (Const64F [auxFrom64F(auxTo64F(c) - auxTo64F(d))])
 
 (Mul8   (Const8 [c])   (Const8 [d]))   -> (Const8  [int64(int8(c*d))])
 (Mul16  (Const16 [c])  (Const16 [d]))  -> (Const16 [int64(int16(c*d))])

diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index d0c6865777da27e3f231e0cb1f570a8072771a5a..ad573635c75828da5b028d5c8bc30dd9d38174a9 100644 (file)
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -957,6 +957,7 @@ func rewriteValuegeneric_OpAdd32F(v *Value) bool {
        v_1 := v.Args[1]
        v_0 := v.Args[0]
        // match: (Add32F (Const32F [c]) (Const32F [d]))
+       // cond: !math.IsNaN(float64(auxTo32F(c) + auxTo32F(d)))
        // result: (Const32F [auxFrom32F(auxTo32F(c) + auxTo32F(d))])
        for {
                for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
@@ -968,6 +969,9 @@ func rewriteValuegeneric_OpAdd32F(v *Value) bool {
                                continue
                        }
                        d := v_1.AuxInt
+                       if !(!math.IsNaN(float64(auxTo32F(c) + auxTo32F(d)))) {
+                               continue
+                       }
                        v.reset(OpConst32F)
                        v.AuxInt = auxFrom32F(auxTo32F(c) + auxTo32F(d))
                        return true
@@ -1233,6 +1237,7 @@ func rewriteValuegeneric_OpAdd64F(v *Value) bool {
        v_1 := v.Args[1]
        v_0 := v.Args[0]
        // match: (Add64F (Const64F [c]) (Const64F [d]))
+       // cond: !math.IsNaN(auxTo64F(c) + auxTo64F(d))
        // result: (Const64F [auxFrom64F(auxTo64F(c) + auxTo64F(d))])
        for {
                for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
@@ -1244,6 +1249,9 @@ func rewriteValuegeneric_OpAdd64F(v *Value) bool {
                                continue
                        }
                        d := v_1.AuxInt
+                       if !(!math.IsNaN(auxTo64F(c) + auxTo64F(d))) {
+                               continue
+                       }
                        v.reset(OpConst64F)
                        v.AuxInt = auxFrom64F(auxTo64F(c) + auxTo64F(d))
                        return true
@@ -22641,6 +22649,7 @@ func rewriteValuegeneric_OpSub32F(v *Value) bool {
        v_1 := v.Args[1]
        v_0 := v.Args[0]
        // match: (Sub32F (Const32F [c]) (Const32F [d]))
+       // cond: !math.IsNaN(float64(auxTo32F(c) - auxTo32F(d)))
        // result: (Const32F [auxFrom32F(auxTo32F(c) - auxTo32F(d))])
        for {
                if v_0.Op != OpConst32F {
@@ -22651,6 +22660,9 @@ func rewriteValuegeneric_OpSub32F(v *Value) bool {
                        break
                }
                d := v_1.AuxInt
+               if !(!math.IsNaN(float64(auxTo32F(c) - auxTo32F(d)))) {
+                       break
+               }
                v.reset(OpConst32F)
                v.AuxInt = auxFrom32F(auxTo32F(c) - auxTo32F(d))
                return true
@@ -22879,6 +22891,7 @@ func rewriteValuegeneric_OpSub64F(v *Value) bool {
        v_1 := v.Args[1]
        v_0 := v.Args[0]
        // match: (Sub64F (Const64F [c]) (Const64F [d]))
+       // cond: !math.IsNaN(auxTo64F(c) - auxTo64F(d))
        // result: (Const64F [auxFrom64F(auxTo64F(c) - auxTo64F(d))])
        for {
                if v_0.Op != OpConst64F {
@@ -22889,6 +22902,9 @@ func rewriteValuegeneric_OpSub64F(v *Value) bool {
                        break
                }
                d := v_1.AuxInt
+               if !(!math.IsNaN(auxTo64F(c) - auxTo64F(d))) {
+                       break
+               }
                v.reset(OpConst64F)
                v.AuxInt = auxFrom64F(auxTo64F(c) - auxTo64F(d))
                return true

diff --git a/test/fixedbugs/issue38359.go b/test/fixedbugs/issue38359.go
new file mode 100644 (file)
index 0000000..a7550c7
--- /dev/null
+++ b/test/fixedbugs/issue38359.go
@@ -0,0 +1,19 @@
+// compile
+
+// Copyright 2020 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.
+
+// Make sure NaN-NaN compiles correctly.
+
+package p
+
+func f() {
+       var st struct {
+               f    float64
+               _, _ string
+       }
+
+       f := 1e308
+       st.f = 2*f - 2*f
+}