[dev.regabi] cmd/compile: stop using Vargen for import/export

Historically, inline function bodies were exported as plain Go source
code, and symbol mangling was a convenient hack because it allowed
variables to be re-imported with largely the same names as they were
originally exported as.

However, nowadays we use a binary format that's more easily extended,
so we can simply serialize all of a function's declared objects up
front, and then refer to them by index later on. This also allows us
to easily report unmangled names all the time (e.g., error message
from issue7921.go).

Fixes #43633.

Change-Id: I46c88f5a47cb921f70ab140976ba9ddce38df216
Reviewed-on: https://go-review.googlesource.com/c/go/+/283193
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
Trust: Dan Scales <danscales@google.com>
Trust: Matthew Dempsky <mdempsky@google.com>

1 files changed, 1 insertions, 26 deletions

diff --git a/src/cmd/compile/internal/typecheck/dcl.go b/src/cmd/compile/internal/typecheck/dcl.go
index ffbf474a58..caa3e8203a 100644
--- a/src/cmd/compile/internal/typecheck/dcl.go
+++ b/src/cmd/compile/internal/typecheck/dcl.go
@@ -7,7 +7,6 @@ package typecheck
 import (
 	"fmt"
 	"strconv"
-	"strings"
 
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
@@ -47,7 +46,6 @@ func Declare(n *ir.Name, ctxt ir.Class) {
 		base.ErrorfAt(n.Pos(), "cannot declare name %v", s)
 	}
 
-	gen := 0
 	if ctxt == ir.PEXTERN {
 		if s.Name == "init" {
 			base.ErrorfAt(n.Pos(), "cannot declare init - must be func")
@@ -66,10 +64,7 @@ func Declare(n *ir.Name, ctxt ir.Class) {
 		}
 		if n.Op() == ir.OTYPE {
 			declare_typegen++
-			gen = declare_typegen
-		} else if n.Op() == ir.ONAME && ctxt == ir.PAUTO && !strings.Contains(s.Name, "·") {
-			vargen++
-			gen = vargen
+			n.Typegen = int32(declare_typegen)
 		}
 		types.Pushdcl(s)
 		n.Curfn = ir.CurFunc
@@ -90,7 +85,6 @@ func Declare(n *ir.Name, ctxt ir.Class) {
 	s.Block = types.Block
 	s.Lastlineno = base.Pos
 	s.Def = n
-	n.Vargen = int32(gen)
 	n.Class = ctxt
 	if ctxt == ir.PFUNC {
 		n.Sym().SetFunc(true)
@@ -338,9 +332,6 @@ func funcarg(n *ir.Field, ctxt ir.Class) {
 	n.Decl = name
 	name.Ntype = n.Ntype
 	Declare(name, ctxt)
-
-	vargen++
-	n.Decl.Vargen = int32(vargen)
 }
 
 func funcarg2(f *types.Field, ctxt ir.Class) {
@@ -358,15 +349,6 @@ func funcargs(nt *ir.FuncType) {
 		base.Fatalf("funcargs %v", nt.Op())
 	}
 
-	// re-start the variable generation number
-	// we want to use small numbers for the return variables,
-	// so let them have the chunk starting at 1.
-	//
-	// TODO(mdempsky): This is ugly, and only necessary because
-	// esc.go uses Vargen to figure out result parameters' index
-	// within the result tuple.
-	vargen = len(nt.Results)
-
 	// declare the receiver and in arguments.
 	if nt.Recv != nil {
 		funcarg(nt.Recv, ir.PPARAM)
@@ -375,9 +357,6 @@ func funcargs(nt *ir.FuncType) {
 		funcarg(n, ir.PPARAM)
 	}
 
-	oldvargen := vargen
-	vargen = 0
-
 	// declare the out arguments.
 	gen := len(nt.Params)
 	for _, n := range nt.Results {
@@ -399,8 +378,6 @@ func funcargs(nt *ir.FuncType) {
 
 		funcarg(n, ir.PPARAMOUT)
 	}
-
-	vargen = oldvargen
 }
 
 // Same as funcargs, except run over an already constructed TFUNC.
@@ -422,8 +399,6 @@ func funcargs2(t *types.Type) {
 	}
 }
 
-var vargen int
-
 func Temp(t *types.Type) *ir.Name {
 	return TempAt(base.Pos, ir.CurFunc, t)
 }