From 7b88b22acf8cb5e32f34e2a396d797c5c0125566 Mon Sep 17 00:00:00 2001
From: Than McIntosh <thanm@google.com>
Date: Tue, 28 Aug 2018 11:27:07 -0400
Subject: [PATCH] cmd/compile: remove var sorting from DWARF inline generation

When generation DWARF inline info records, the current implementation
includes a sorting pass that reorders a subprogram's child variable
DIEs based on class (param/auto) and name. This sorting is no longer
needed, and can cause problems for a debugger (if we want to use the
DWARF info for creating a call to an optimized function); this patch
removes it.

Ordering of DWARF subprogram variable/parameter DIEs is still
deterministic with this change, since it is keyed off the order in
which vars appear in the pre-inlining function "Dcl" list.

Updates #27039

Change-Id: I3b91290d11bb3b9b36fb61271d80b801841401ee
Reviewed-on: https://go-review.googlesource.com/131895
Reviewed-by: Heschi Kreinick <heschi@google.com>
---
 src/cmd/compile/internal/gc/dwinl.go | 27 ---------------------------
 src/cmd/compile/internal/gc/pgen.go  | 27 ---------------------------
 2 files changed, 54 deletions(-)

diff --git a/src/cmd/compile/internal/gc/dwinl.go b/src/cmd/compile/internal/gc/dwinl.go
index d191b7ba6c84c4..51251c9139fd24 100644
--- a/src/cmd/compile/internal/gc/dwinl.go
+++ b/src/cmd/compile/internal/gc/dwinl.go
@@ -8,7 +8,6 @@ import (
 	"cmd/internal/dwarf"
 	"cmd/internal/obj"
 	"cmd/internal/src"
-	"sort"
 	"strings"
 )
 
@@ -96,7 +95,6 @@ func assembleInlines(fnsym *obj.LSym, dwVars []*dwarf.Var) dwarf.InlCalls {
 	// the pre-inlining decls for the target function and assign child
 	// index accordingly.
 	for ii, sl := range vmap {
-		sort.Sort(byClassThenName(sl))
 		var m map[varPos]int
 		if ii == 0 {
 			if !fnsym.WasInlined() {
@@ -311,31 +309,6 @@ func beginRange(calls []dwarf.InlCall, p *obj.Prog, ii int, imap map[int]int) *d
 	return &call.Ranges[len(call.Ranges)-1]
 }
 
-func cmpDwarfVar(a, b *dwarf.Var) bool {
-	// named before artificial
-	aart := 0
-	if strings.HasPrefix(a.Name, "~r") {
-		aart = 1
-	}
-	bart := 0
-	if strings.HasPrefix(b.Name, "~r") {
-		bart = 1
-	}
-	if aart != bart {
-		return aart < bart
-	}
-
-	// otherwise sort by name
-	return a.Name < b.Name
-}
-
-// byClassThenName implements sort.Interface for []*dwarf.Var using cmpDwarfVar.
-type byClassThenName []*dwarf.Var
-
-func (s byClassThenName) Len() int           { return len(s) }
-func (s byClassThenName) Less(i, j int) bool { return cmpDwarfVar(s[i], s[j]) }
-func (s byClassThenName) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
-
 func dumpInlCall(inlcalls dwarf.InlCalls, idx, ilevel int) {
 	for i := 0; i < ilevel; i++ {
 		Ctxt.Logf("  ")
diff --git a/src/cmd/compile/internal/gc/pgen.go b/src/cmd/compile/internal/gc/pgen.go
index cf1164772b0fca..7f20643ab57feb 100644
--- a/src/cmd/compile/internal/gc/pgen.go
+++ b/src/cmd/compile/internal/gc/pgen.go
@@ -15,7 +15,6 @@ import (
 	"fmt"
 	"math/rand"
 	"sort"
-	"strings"
 	"sync"
 	"time"
 )
@@ -594,35 +593,9 @@ func preInliningDcls(fnsym *obj.LSym) []*Node {
 		}
 		rdcl = append(rdcl, n)
 	}
-	sort.Sort(byNodeName(rdcl))
 	return rdcl
 }
 
-func cmpNodeName(a, b *Node) bool {
-	aart := 0
-	if strings.HasPrefix(a.Sym.Name, "~") {
-		aart = 1
-	}
-	bart := 0
-	if strings.HasPrefix(b.Sym.Name, "~") {
-		bart = 1
-	}
-	if aart != bart {
-		return aart < bart
-	}
-
-	aname := unversion(a.Sym.Name)
-	bname := unversion(b.Sym.Name)
-	return aname < bname
-}
-
-// byNodeName implements sort.Interface for []*Node using cmpNodeName.
-type byNodeName []*Node
-
-func (s byNodeName) Len() int           { return len(s) }
-func (s byNodeName) Less(i, j int) bool { return cmpNodeName(s[i], s[j]) }
-func (s byNodeName) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
-
 // stackOffset returns the stack location of a LocalSlot relative to the
 // stack pointer, suitable for use in a DWARF location entry. This has nothing
 // to do with its offset in the user variable.