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gc: fix order of operations for f() < g().

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Also, 6g was passing uninitialized
Node &n2 to regalloc, causing non-deterministic
register collisions (but only when both left and
right hand side of comparison had function calls).

Fixes #1728.

R=ken2
CC=golang-dev
https://golang.org/cl/4425070
This commit is contained in:
Russ Cox 2011-04-26 00:57:03 -04:00
parent f813702f6d
commit bac8f18035
4 changed files with 50 additions and 21 deletions
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18
src/cmd/5g/cgen.c
View File

@ -962,7 +962,7 @@ bgen(Node *n, int true, Prog *to)
}
// make simplest on right
if(nl->op == OLITERAL || nl->ullman < nr->ullman) {
if(nl->op == OLITERAL || (nl->ullman < UINF && nl->ullman < nr->ullman)) {
a = brrev(a);
r = nl;
nl = nr;
@ -1073,18 +1073,18 @@ bgen(Node *n, int true, Prog *to)
a = optoas(a, nr->type);
if(nr->ullman >= UINF) {
regalloc(&n1, nr->type, N);
cgen(nr, &n1);
tempname(&tmp, nr->type);
gmove(&n1, &tmp);
regfree(&n1);
regalloc(&n1, nl->type, N);
cgen(nl, &n1);
tempname(&tmp, nl->type);
gmove(&n1, &tmp);
regfree(&n1);
regalloc(&n2, nr->type, N);
cgen(&tmp, &n2);
cgen(nr, &n2);
regalloc(&n1, nl->type, N);
cgen(&tmp, &n1);
gcmp(optoas(OCMP, nr->type), &n1, &n2);
patch(gbranch(a, nr->type), to);

20
src/cmd/6g/cgen.c
View File

@ -829,7 +829,7 @@ bgen(Node *n, int true, Prog *to)
}
// make simplest on right
if(nl->op == OLITERAL || nl->ullman < nr->ullman) {
if(nl->op == OLITERAL || (nl->ullman < nr->ullman && nl->ullman < UINF)) {
a = brrev(a);
r = nl;
nl = nr;
@ -879,18 +879,18 @@ bgen(Node *n, int true, Prog *to)
}
if(nr->ullman >= UINF) {
regalloc(&n1, nr->type, N);
cgen(nr, &n1);
tempname(&tmp, nr->type);
gmove(&n1, &tmp);
regfree(&n1);
regalloc(&n1, nl->type, N);
cgen(nl, &n1);
regalloc(&n2, nr->type, &n2);
cgen(&tmp, &n2);
tempname(&tmp, nl->type);
gmove(&n1, &tmp);
regfree(&n1);
regalloc(&n2, nr->type, N);
cgen(nr, &n2);
regalloc(&n1, nl->type, N);
cgen(&tmp, &n1);
goto cmp;
}

4
src/cmd/8g/cgen.c
View File

@ -900,7 +900,7 @@ bgen(Node *n, int true, Prog *to)
}
// make simplest on right
if(nl->op == OLITERAL || nl->ullman < nr->ullman) {
if(nl->op == OLITERAL || (nl->ullman < nr->ullman && nl->ullman < UINF)) {
a = brrev(a);
r = nl;
nl = nr;
@ -1025,8 +1025,8 @@ bgen(Node *n, int true, Prog *to)
if(nr->ullman >= UINF) {
tempname(&n1, nl->type);
tempname(&tmp, nr->type);
cgen(nr, &tmp);
cgen(nl, &n1);
cgen(nr, &tmp);
regalloc(&n2, nr->type, N);
cgen(&tmp, &n2);
goto cmp;

29
test/func7.go Normal file
View File

@ -0,0 +1,29 @@
// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2011 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.
package main
var calledf = false
func f() int {
calledf = true
return 1
}
func g() int {
if !calledf {
println("BUG: func7 - called g before f")
}
return 0
}
func main() {
// 6g, 8g, 5g all used to evaluate g() before f().
if f() < g() {
panic("wrong answer")
}
}