blob: f5bca16a3240bb7e2f40eda6ed93f18bbaf0cece [file] [log] [blame]
// run
// +build !nacl
// 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.
// Runs a build -S to capture the assembly language
// output, checks that the line numbers associated with
// the stream of instructions do not change "too much".
// The changes that fixes this (that reduces the amount
// of change) does so by treating register spill, reload,
// copy, and rematerializations as being "unimportant" and
// just assigns them the line numbers of whatever "real"
// instructions preceded them.
// nacl is excluded because this runs a compiler.
package main
import (
"bufio"
"bytes"
"fmt"
"os"
"os/exec"
"strconv"
"strings"
)
// updateEnv modifies env to ensure that key=val
func updateEnv(env *[]string, key, val string) {
if val != "" {
var found bool
key = key + "="
for i, kv := range *env {
if strings.HasPrefix(kv, key) {
(*env)[i] = key + val
found = true
break
}
}
if !found {
*env = append(*env, key+val)
}
}
}
func main() {
testarch := os.Getenv("TESTARCH") // Targets other platform in test compilation.
debug := os.Getenv("TESTDEBUG") != "" // Output the relevant assembly language.
cmd := exec.Command("go", "build", "-gcflags", "-S", "fixedbugs/issue18902b.go")
var buf bytes.Buffer
cmd.Stdout = &buf
cmd.Stderr = &buf
cmd.Env = os.Environ()
updateEnv(&cmd.Env, "GOARCH", testarch)
err := cmd.Run()
if err != nil {
fmt.Printf("%s\n%s", err, buf.Bytes())
return
}
begin := "\"\".(*gcSortBuf).flush" // Text at beginning of relevant dissassembly.
s := buf.String()
i := strings.Index(s, begin)
if i < 0 {
fmt.Printf("Failed to find expected symbol %s in output\n%s\n", begin, s)
return
}
s = s[i:]
r := strings.NewReader(s)
scanner := bufio.NewScanner(r)
first := true // The first line after the begin text will be skipped
beforeLineNumber := "issue18902b.go:" // Text preceding line number in each line.
lbln := len(beforeLineNumber)
var scannedCount, changes, sumdiffs float64
prevVal := 0
for scanner.Scan() {
line := scanner.Text()
if first {
first = false
continue
}
i = strings.Index(line, beforeLineNumber)
if i < 0 {
// Done reading lines
if scannedCount < 200 { // When test was written, 251 lines observed on amd64
fmt.Printf("Scanned only %d lines, was expecting more than 200", scannedCount)
return
}
// Note: when test was written, before changes=92, after=50 (was 62 w/o rematerialization NoXPos in *Value.copyInto())
// and before sumdiffs=784, after=180 (was 446 w/o rematerialization NoXPos in *Value.copyInto())
// Set the dividing line between pass and fail at the midpoint.
// Normalize against instruction count in case we unroll loops, etc.
if changes/scannedCount >= (50+92)/(2*scannedCount) || sumdiffs/scannedCount >= (180+784)/(2*scannedCount) {
fmt.Printf("Line numbers change too much, # of changes=%.f, sumdiffs=%.f, # of instructions=%.f\n", changes, sumdiffs, scannedCount)
}
return
}
scannedCount++
i += lbln
lineVal, err := strconv.Atoi(line[i : i+3])
if err != nil {
fmt.Printf("Expected 3-digit line number after %s in %s\n", beforeLineNumber, line)
}
if prevVal == 0 {
prevVal = lineVal
}
diff := lineVal - prevVal
if diff < 0 {
diff = -diff
}
if diff != 0 {
changes++
sumdiffs += float64(diff)
}
// If things change too much, set environment variable TESTDEBUG to help figure out what's up.
// The "before" behavior can be recreated in DebugFriendlySetPosFrom (currently in gc/ssa.go)
// by inserting unconditional
// s.SetPos(v.Pos)
// at the top of the function.
if debug {
fmt.Printf("%d %.f %.f %s\n", lineVal, changes, sumdiffs, line)
}
prevVal = lineVal
}
if err := scanner.Err(); err != nil {
fmt.Println("Reading standard input:", err)
return
}
}