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cmd/compile: make cmpstackvarlt properly asymmetric

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Previously, given two Nodes n1 and n2 of different non-PAUTO classes
(e.g., PPARAM and PPARAMOUT), cmpstackvarlt(n1, n2) and
cmpstackvarlt(n2, n1) both returned true, which is nonsense.

This doesn't seem to cause any visible miscompilation problems, but
notably fixing it does cause toolstash/buildall to fail.

Change-Id: I33b2c66e902c5eced875d8fbf18b7cfdc81e8aed
Reviewed-on: https://go-review.googlesource.com/19778
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Matthew Dempsky 2016-02-20 21:36:12 -08:00
parent 8847a5913a
commit 5609a48931
2 changed files with 19 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
src/cmd/compile/internal/gc/pgen.go
View File

@ -186,21 +186,12 @@ func emitptrargsmap() {
// the top of the stack and increasing in size. // the top of the stack and increasing in size.
// Non-autos sort on offset. // Non-autos sort on offset.
func cmpstackvarlt(a, b *Node) bool { func cmpstackvarlt(a, b *Node) bool {
if a.Class != b.Class { if (a.Class == PAUTO) != (b.Class == PAUTO) {
if a.Class == PAUTO { return b.Class == PAUTO
return false
}
return true
} }
if a.Class != PAUTO { if a.Class != PAUTO {
if a.Xoffset < b.Xoffset { return a.Xoffset < b.Xoffset
return true
}
if a.Xoffset > b.Xoffset {
return false
}
return false
} }
if a.Used != b.Used { if a.Used != b.Used {
@ -219,11 +210,8 @@ func cmpstackvarlt(a, b *Node) bool {
return ap return ap
} }
if a.Type.Width < b.Type.Width { if a.Type.Width != b.Type.Width {
return false return a.Type.Width > b.Type.Width
}
if a.Type.Width > b.Type.Width {
return true
} }
return a.Sym.Name < b.Sym.Name return a.Sym.Name < b.Sym.Name

14
src/cmd/compile/internal/gc/pgen_test.go
View File

@ -40,6 +40,16 @@ func TestCmpstackvar(t *testing.T) {
Node{Class: PFUNC, Xoffset: 10}, Node{Class: PFUNC, Xoffset: 10},
false, false,
}, },
{
Node{Class: PPARAM, Xoffset: 10},
Node{Class: PPARAMOUT, Xoffset: 20},
true,
},
{
Node{Class: PPARAMOUT, Xoffset: 10},
Node{Class: PPARAM, Xoffset: 20},
true,
},
{ {
Node{Class: PAUTO, Used: true}, Node{Class: PAUTO, Used: true},
Node{Class: PAUTO, Used: false}, Node{Class: PAUTO, Used: false},
@ -101,6 +111,10 @@ func TestCmpstackvar(t *testing.T) {
if got != d.lt { if got != d.lt {
t.Errorf("want %#v < %#v", d.a, d.b) t.Errorf("want %#v < %#v", d.a, d.b)
} }
// If we expect a < b to be true, check that b < a is false.
if d.lt && cmpstackvarlt(&d.b, &d.a) {
t.Errorf("unexpected %#v < %#v", d.b, d.a)
}
} }
} }