From 7c9225a018bb6a8ae1fa66ec4a74cfb6872951b5 Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josharian@gmail.com>
Date: Fri, 15 May 2015 08:27:03 -0700
Subject: [PATCH] cmd/internal/gc: rearrange Node fields

Rearrange Node fields to enable better struct packing.
This reduces readability in favor of shrinking
the size of Nodes.

This reduces the size of Node from 368 to 344.
This reduces the memory usage to compile the
rotate tests by about 5.6%.

No functional changes. Passes toolstash -cmp.

Updates #9933.

Change-Id: I2764c5847fb1635ddc898e2ee385d007d67f03c5
---
 src/cmd/internal/gc/go.go     |   4 +-
 src/cmd/internal/gc/syntax.go | 100 ++++++++++++++++++----------------
 2 files changed, 56 insertions(+), 48 deletions(-)

diff --git a/src/cmd/internal/gc/go.go b/src/cmd/internal/gc/go.go
index f116e6020a711b..d520bf1b7d2798 100644
--- a/src/cmd/internal/gc/go.go
+++ b/src/cmd/internal/gc/go.go
@@ -82,14 +82,14 @@ type Mpcplx struct {
 }
 
 type Val struct {
-	Ctype int16
 	// U contains one of:
 	// bool     bool when Ctype == CTBOOL
 	// *Mpint   int when Ctype == CTINT, rune when Ctype == CTRUNE
 	// *Mpflt   float when Ctype == CTFLT
 	// *Mpcplx  pair of floats when Ctype == CTCPLX
 	// string   string when Ctype == CTSTR
-	U interface{}
+	U     interface{}
+	Ctype int16
 }
 
 type Pkg struct {
diff --git a/src/cmd/internal/gc/syntax.go b/src/cmd/internal/gc/syntax.go
index c5dd0c7c325659..49e31751a1156a 100644
--- a/src/cmd/internal/gc/syntax.go
+++ b/src/cmd/internal/gc/syntax.go
@@ -23,32 +23,6 @@ type Node struct {
 	List  *NodeList
 	Rlist *NodeList
 
-	Op          uint8
-	Nointerface bool
-	Ullman      uint8 // sethi/ullman number
-	Addable     bool  // addressable
-	Etype       uint8 // op for OASOP, etype for OTYPE, exclam for export
-	Bounded     bool  // bounds check unnecessary
-	Class       uint8 // PPARAM, PAUTO, PEXTERN, etc
-	Embedded    uint8 // ODCLFIELD embedded type
-	Colas       bool  // OAS resulting from :=
-	Diag        uint8 // already printed error about this
-	Noescape    bool  // func arguments do not escape; TODO(rsc): move Noescape to Func struct (see CL 7360)
-	Walkdef     uint8
-	Typecheck   uint8
-	Local       bool
-	Dodata      uint8
-	Initorder   uint8
-	Used        bool
-	Isddd       bool // is the argument variadic
-	Implicit    bool
-	Addrtaken   bool   // address taken, even if not moved to heap
-	Assigned    bool   // is the variable ever assigned to
-	Likely      int8   // likeliness of if statement
-	Hasbreak    bool   // has break statement
-	Esc         uint16 // EscXXX
-	Funcdepth   int32
-
 	// most nodes
 	Type  *Type
 	Orig  *Node // original form, for printing, and tracking copies of ONAMEs
@@ -57,12 +31,6 @@ type Node struct {
 	// func
 	Func *Func
 
-	// OLITERAL
-	Val Val
-
-	// OREGISTER, OINDREG
-	Reg int16
-
 	// ONAME
 	*Name
 	Ntype    *Node
@@ -76,10 +44,9 @@ type Node struct {
 	Stackparam *Node // OPARAM node referring to stack copy of param
 	Alloc      *Node // allocation call
 
-	// ONAME closure param with PPARAMREF
-	Outer   *Node         // outer PPARAMREF in nested closure
-	Closure *Node         // ONAME/PHEAP <-> ONAME/PPARAMREF
-	Top     TypecheckCtxt // top context (Ecall, Eproc, etc)
+	// ONAME closure param with PPARAMREF (see also the Top field, below)
+	Outer   *Node // outer PPARAMREF in nested closure
+	Closure *Node // ONAME/PHEAP <-> ONAME/PPARAMREF
 
 	// OPACK
 	Pkg *Pkg
@@ -88,20 +55,61 @@ type Node struct {
 	Initplan *InitPlan
 
 	// Escape analysis.
-	Escflowsrc   *NodeList // flow(this, src)
-	Escretval    *NodeList // on OCALLxxx, list of dummy return values
-	Escloopdepth int32     // -1: global, 0: return variables, 1:function top level, increased inside function for every loop or label to mark scopes
+	Escflowsrc *NodeList // flow(this, src)
+	Escretval  *NodeList // on OCALLxxx, list of dummy return values
+
+	Sym *Sym // various
+
+	Opt interface{} // for optimization passes
+
+	// OLITERAL
+	Val Val
 
-	Sym      *Sym  // various
-	Vargen   int32 // unique name for OTYPE/ONAME within a function.  Function outputs are numbered starting at one.
-	Lineno   int32
 	Xoffset  int64
 	Stkdelta int64 // offset added by stack frame compaction phase.
-	Ostk     uint8 // 6g only
-	Iota     int32
-	Walkgen  uint32
+
+	// Escape analysis.
+	Escloopdepth int32 // -1: global, 0: return variables, 1:function top level, increased inside function for every loop or label to mark scopes
+
+	Vargen  int32 // unique name for OTYPE/ONAME within a function.  Function outputs are numbered starting at one.
+	Lineno  int32
+	Iota    int32
+	Walkgen uint32
+
+	Funcdepth int32
+
+	// OREGISTER, OINDREG
+	Reg int16
+
+	Top TypecheckCtxt // top context (Ecall, Eproc, etc) in ONAME closure param with PPARAMREF
+
 	Esclevel Level
-	Opt      interface{} // for optimization passes
+	Esc      uint16 // EscXXX
+
+	Op          uint8
+	Nointerface bool
+	Ullman      uint8 // sethi/ullman number
+	Addable     bool  // addressable
+	Etype       uint8 // op for OASOP, etype for OTYPE, exclam for export
+	Bounded     bool  // bounds check unnecessary
+	Class       uint8 // PPARAM, PAUTO, PEXTERN, etc
+	Embedded    uint8 // ODCLFIELD embedded type
+	Colas       bool  // OAS resulting from :=
+	Diag        uint8 // already printed error about this
+	Noescape    bool  // func arguments do not escape; TODO(rsc): move Noescape to Func struct (see CL 7360)
+	Walkdef     uint8
+	Typecheck   uint8
+	Local       bool
+	Dodata      uint8
+	Initorder   uint8
+	Used        bool
+	Isddd       bool // is the argument variadic
+	Implicit    bool
+	Addrtaken   bool  // address taken, even if not moved to heap
+	Assigned    bool  // is the variable ever assigned to
+	Likely      int8  // likeliness of if statement
+	Hasbreak    bool  // has break statement
+	Ostk        uint8 // 6g only
 }
 
 // Name holds Node fields used only by ONAME nodes.