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cmd/compile: fix abbrev selection for output params

In Cl 302071 we changed the compiler to use a different recipe for
selecting the DWARF frame offset for output parameters, to reflect the
fact that registerized output params don't have a stack memory
location on entry to the function. In the process, however, we
switched from using an abbrev pf DW_ABRV_PARAM to an abbrev of
DW_ABRV_AUTO, which means that Delve can't recognize them correctly.
To fix the problem, switch back to picking the correct abbrev entry,
while leaving the new offset recipe intact.

Updates #40724.
Updates #45720.

Change-Id: If721c9255bcd030177806576cde3450563f7a235
Reviewed-on: https://go-review.googlesource.com/c/go/+/315610
Trust: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Than McIntosh 2021-04-30 11:15:44 -04:00
parent d19eece91f
commit 41afd3af42
2 changed files with 125 additions and 10 deletions

View File

@ -268,23 +268,28 @@ func createSimpleVar(fnsym *obj.LSym, n *ir.Name) *dwarf.Var {
var abbrev int
var offs int64
switch n.Class {
case ir.PPARAM, ir.PPARAMOUT:
if !n.IsOutputParamInRegisters() {
abbrev = dwarf.DW_ABRV_PARAM
offs = n.FrameOffset() + base.Ctxt.FixedFrameSize()
break
}
fallthrough
case ir.PAUTO:
localAutoOffset := func() int64 {
offs = n.FrameOffset()
abbrev = dwarf.DW_ABRV_AUTO
if base.Ctxt.FixedFrameSize() == 0 {
offs -= int64(types.PtrSize)
}
if buildcfg.FramePointerEnabled {
offs -= int64(types.PtrSize)
}
return offs
}
switch n.Class {
case ir.PAUTO:
offs = localAutoOffset()
abbrev = dwarf.DW_ABRV_AUTO
case ir.PPARAM, ir.PPARAMOUT:
abbrev = dwarf.DW_ABRV_PARAM
if n.IsOutputParamInRegisters() {
offs = localAutoOffset()
} else {
offs = n.FrameOffset() + base.Ctxt.FixedFrameSize()
}
default:
base.Fatalf("createSimpleVar unexpected class %v for node %v", n.Class, n)

View File

@ -19,6 +19,7 @@ import (
"path/filepath"
"reflect"
"runtime"
"sort"
"strconv"
"strings"
"testing"
@ -1641,3 +1642,112 @@ func TestIssue42484(t *testing.T) {
}
f.Close()
}
func TestOutputParamAbbrevAndAttr(t *testing.T) {
testenv.MustHaveGoBuild(t)
if runtime.GOOS == "plan9" {
t.Skip("skipping on plan9; no DWARF symbol table in executables")
}
t.Parallel()
// This test verifies that the compiler is selecting the correct
// DWARF abbreviation for output parameters, and that the
// variable parameter attribute is correct for in-params and
// out-params.
const prog = `
package main
//go:noinline
func ABC(p1, p2, p3 int, f1, f2, f3 float32, b1 [1024]int) (r1 int, r2 int, r3 [1024]int, r4 byte) {
b1[0] = 6
r1, r2, r3, r4 = p3, p2, b1, 'a'
return
}
func main() {
a := [1024]int{}
v1, v2, v3, v4 := ABC(1, 2, 3, 1.0, 2.0, 1.0, a)
println(v1, v2, v3[0], v4)
}
`
dir := t.TempDir()
f := gobuild(t, dir, prog, NoOpt)
defer f.Close()
d, err := f.DWARF()
if err != nil {
t.Fatalf("error reading DWARF: %v", err)
}
rdr := d.Reader()
ex := examiner{}
if err := ex.populate(rdr); err != nil {
t.Fatalf("error reading DWARF: %v", err)
}
// Locate the main.ABC DIE
abcs := ex.Named("main.ABC")
if len(abcs) == 0 {
t.Fatalf("unable to locate DIE for main.ABC")
}
if len(abcs) != 1 {
t.Fatalf("more than one main.ABC DIE")
}
abcdie := abcs[0]
// Vet the DIE
if abcdie.Tag != dwarf.TagSubprogram {
t.Fatalf("unexpected tag %v on main.ABC DIE", abcdie.Tag)
}
// A setting of DW_AT_variable_parameter indicates that the
// param in question is an output parameter; we want to see this
// attribute set to TRUE for all Go return params. It would be
// OK to have it missing for input parameters, but for the moment
// we verify that the attr is present but set to false.
// Values in this map:
//
// 0: <no param of this name>
// -1: varparm attr not found
// 1: varparm found with value false
// 2: varparm found with value true
//
foundParams := make(map[string]int)
// Walk ABCs's children looking for params.
abcIdx := ex.idxFromOffset(abcdie.Offset)
childDies := ex.Children(abcIdx)
for _, child := range childDies {
if child.Tag == dwarf.TagFormalParameter {
st := -1
if vp, ok := child.Val(dwarf.AttrVarParam).(bool); ok {
if vp {
st = 2
} else {
st = 1
}
}
if name, ok := child.Val(dwarf.AttrName).(string); ok {
foundParams[name] = st
}
}
}
// Digest the result.
found := make([]string, 0, len(foundParams))
for k, v := range foundParams {
found = append(found, fmt.Sprintf("%s:%d", k, v))
}
sort.Strings(found)
// Make sure we see all of the expected params, that they have
// the varparam attr, and the varparm is set for the returns.
expected := "[b1:1 f1:1 f2:1 f3:1 p1:1 p2:1 p3:1 r1:2 r2:2 r3:2 r4:2]"
if fmt.Sprintf("%+v", found) != expected {
t.Errorf("param check failed, wanted %s got %s\n",
expected, found)
}
}