From 7c2c0b4e533d3d75df8993eb87f6948c49c04cc8 Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josharian@gmail.com>
Date: Mon, 16 Mar 2015 16:31:13 -0700
Subject: [PATCH] [dev.ssa] cmd/internal/ssa: minor cleanup

These were review comments for CL 6681 that didn't get sent in time.

Change-Id: If161af3655770487f3ba34535d3fb55dbfde7917
Reviewed-on: https://go-review.googlesource.com/7644
Reviewed-by: Keith Randall <khr@golang.org>
---
 src/cmd/internal/ssa/deadcode.go | 13 ++++++++-----
 src/cmd/internal/ssa/op.go       |  2 +-
 src/cmd/internal/ssa/type.go     |  2 +-
 src/cmd/internal/ssa/value.go    |  9 ++++++++-
 4 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/cmd/internal/ssa/deadcode.go b/src/cmd/internal/ssa/deadcode.go
index 1647ea955d..e8c8bfcc03 100644
--- a/src/cmd/internal/ssa/deadcode.go
+++ b/src/cmd/internal/ssa/deadcode.go
@@ -86,8 +86,10 @@ func deadcode(f *Func) {
 				f.vid.put(v.ID)
 			}
 		}
-		for j := i; j < len(b.Values); j++ {
-			b.Values[j] = nil // aid GC
+		// aid GC
+		tail := b.Values[i:]
+		for j := range tail {
+			tail[j] = nil
 		}
 		b.Values = b.Values[:i]
 	}
@@ -105,9 +107,10 @@ func deadcode(f *Func) {
 			f.bid.put(b.ID)
 		}
 	}
-	// zero remainder to help gc
-	for j := i; j < len(f.Blocks); j++ {
-		f.Blocks[j] = nil
+	// zero remainder to help GC
+	tail := f.Blocks[i:]
+	for j := range tail {
+		tail[j] = nil
 	}
 	f.Blocks = f.Blocks[:i]
 
diff --git a/src/cmd/internal/ssa/op.go b/src/cmd/internal/ssa/op.go
index a4364b1c5c..905d62b69c 100644
--- a/src/cmd/internal/ssa/op.go
+++ b/src/cmd/internal/ssa/op.go
@@ -82,7 +82,7 @@ const (
 	OpStoreFP
 	OpStoreSP
 
-	// spill&restore ops for the register allocator.  These are
+	// spill and restore ops for the register allocator.  These are
 	// semantically identical to OpCopy - they do not take/return
 	// stores like regular memory ops do.  We can get away with that because
 	// we know there is no aliasing to spill slots on the stack.
diff --git a/src/cmd/internal/ssa/type.go b/src/cmd/internal/ssa/type.go
index 3389622c74..e9c017d38a 100644
--- a/src/cmd/internal/ssa/type.go
+++ b/src/cmd/internal/ssa/type.go
@@ -34,7 +34,7 @@ var (
 	TypeFlags = &Flags{}
 )
 
-// typeIdentical returns whether it two arguments are the same type.
+// typeIdentical reports whether its two arguments are the same type.
 func typeIdentical(t, u Type) bool {
 	if t == TypeMem {
 		return u == TypeMem
diff --git a/src/cmd/internal/ssa/value.go b/src/cmd/internal/ssa/value.go
index 740525a5f5..f6f099cd32 100644
--- a/src/cmd/internal/ssa/value.go
+++ b/src/cmd/internal/ssa/value.go
@@ -24,7 +24,7 @@ type Value struct {
 	// are a few other pseudo-types, see type.go.
 	Type Type
 
-	// Auxiliary info for this value.  The type of this information depends on the opcode (& type).
+	// Auxiliary info for this value.  The type of this information depends on the opcode and type.
 	Aux interface{}
 
 	// Arguments of this value
@@ -67,9 +67,15 @@ func (v *Value) LongString() string {
 }
 
 func (v *Value) AddArg(w *Value) {
+	if v.Args == nil {
+		v.resetArgs() // use argstorage
+	}
 	v.Args = append(v.Args, w)
 }
 func (v *Value) AddArgs(a ...*Value) {
+	if v.Args == nil {
+		v.resetArgs() // use argstorage
+	}
 	v.Args = append(v.Args, a...)
 }
 func (v *Value) SetArg(i int, w *Value) {
@@ -77,6 +83,7 @@ func (v *Value) SetArg(i int, w *Value) {
 }
 func (v *Value) RemoveArg(i int) {
 	copy(v.Args[i:], v.Args[i+1:])
+	v.Args[len(v.Args)-1] = nil // aid GC
 	v.Args = v.Args[:len(v.Args)-1]
 }
 func (v *Value) SetArgs1(a *Value) {