cmd/compile: fix racewalk{enter,exit} removal

We can't remove race instrumentation unless there are no calls,
not just no static calls. Closure and interface calls also count.

The problem in issue 29329 is that there was a racefuncenter, an
InterCall, and a racefuncexit.  The racefuncenter was removed, then
the InterCall was rewritten to a StaticCall. That prevented the
racefuncexit from being removed. That caused an imbalance in
racefuncenter/racefuncexit calls, which made the race detector barf.

Bug introduced at CL 121235

Fixes #29329

Change-Id: I2c94ac6cf918dd910b74b2a0de5dc2480d236f16
Reviewed-on: https://go-review.googlesource.com/c/155917
Run-TryBot: Keith Randall <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: randall77

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

@@ -1111,7 +1111,8 @@ func needRaceCleanup(sym interface{}, v *Value) bool {
 	}
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
-			if v.Op == OpStaticCall {
+			switch v.Op {
+			case OpStaticCall:
 				switch v.Aux.(fmt.Stringer).String() {
 				case "runtime.racefuncenter", "runtime.racefuncexit", "runtime.panicindex",
 					"runtime.panicslice", "runtime.panicdivide", "runtime.panicwrap":
@@ -1122,6 +1123,9 @@ func needRaceCleanup(sym interface{}, v *Value) bool {
 					// for accurate stacktraces.
 					return false
 				}
+			case OpClosureCall, OpInterCall:
+				// We must keep the race functions if there are any other call types.
+				return false
 			}
 		}
 	}

test/fixedbugs/issue29329.go

@@ -0,0 +1,106 @@
+// run -race
+
+// Copyright 2018 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.
+
+// +build linux,amd64
+
+package main
+
+import (
+	"fmt"
+)
+
+type LineString []Point
+type Point [2]float64
+
+//go:noinline
+func benchmarkData() LineString {
+	return LineString{{1.0, 2.0}}
+}
+
+func (ls LineString) Clone() LineString {
+	ps := MultiPoint(ls)
+	return LineString(ps.Clone())
+}
+
+type MultiPoint []Point
+
+func (mp MultiPoint) Clone() MultiPoint {
+	if mp == nil {
+		return nil
+	}
+
+	points := make([]Point, len(mp))
+	copy(points, mp)
+
+	return MultiPoint(points)
+}
+
+func F1() {
+	cases := []struct {
+		threshold float64
+		length    int
+	}{
+		{0.1, 1118},
+		{0.5, 257},
+		{1.0, 144},
+		{1.5, 95},
+		{2.0, 71},
+		{3.0, 46},
+		{4.0, 39},
+		{5.0, 33},
+	}
+
+	ls := benchmarkData()
+
+	for k := 0; k < 100; k++ {
+		for i, tc := range cases {
+			r := DouglasPeucker(tc.threshold).LineString(ls.Clone())
+			if len(r) == tc.length {
+				fmt.Printf("%d: unexpected\n", i)
+			}
+		}
+	}
+}
+
+// A DouglasPeuckerSimplifier wraps the DouglasPeucker function.
+type DouglasPeuckerSimplifier struct {
+	Threshold float64
+}
+
+// DouglasPeucker creates a new DouglasPeuckerSimplifier.
+func DouglasPeucker(threshold float64) *DouglasPeuckerSimplifier {
+	return &DouglasPeuckerSimplifier{
+		Threshold: threshold,
+	}
+}
+
+func (s *DouglasPeuckerSimplifier) LineString(ls LineString) LineString {
+	return lineString(s, ls)
+}
+
+type simplifier interface {
+	simplify(LineString, bool) (LineString, []int)
+}
+
+func lineString(s simplifier, ls LineString) LineString {
+	return runSimplify(s, ls)
+}
+
+func runSimplify(s simplifier, ls LineString) LineString {
+	if len(ls) <= 2 {
+		return ls
+	}
+	ls, _ = s.simplify(ls, false)
+	return ls
+}
+
+func (s *DouglasPeuckerSimplifier) simplify(ls LineString, wim bool) (LineString, []int) {
+	return nil, nil
+}
+
+func main() {
+	F1()
+}