cmd/compile/internal/ssa: lower builtins much later

* Move lowering into a separate pass.
* SliceLen/SliceCap is now available to various intermediate passes
which use useful for bounds checking.
* Add a second opt pass to handle the new opportunities

Decreases the code size of binaries in pkg/tool/linux_amd64
by ~45K.

Updates #14564 #14606

Change-Id: I5b2bd6202181c50623a3585fbf15c0d6db6d4685
Reviewed-on: https://go-review.googlesource.com/20172
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/ssa/compile.go

@@ -182,6 +182,8 @@ var passes = [...]pass{
 	{name: "phiopt", fn: phiopt},
 	{name: "nilcheckelim", fn: nilcheckelim},
 	{name: "prove", fn: prove},
+	{name: "dec", fn: dec, required: true},
+	{name: "late opt", fn: opt}, // TODO: split required rules and optimizing rules
 	{name: "generic deadcode", fn: deadcode},
 	{name: "fuse", fn: fuse},
 	{name: "dse", fn: dse},

src/cmd/compile/internal/ssa/gen/dec.rules

+(StringPtr (StringMake ptr _)) -> ptr
+(StringLen (StringMake _ len)) -> len
+
+(SlicePtr (SliceMake ptr _ _ )) -> ptr
+(SliceLen (SliceMake _ len _)) -> len
+(SliceCap (SliceMake _ _ cap)) -> cap

src/cmd/compile/internal/ssa/gen/decOps.go

+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+var decOps = []opData{}
+
+var decBlocks = []blockData{}
+
+func init() {
+	archs = append(archs, arch{"dec", decOps, decBlocks, nil})
+}

src/cmd/compile/internal/ssa/gen/generic.rules

@@ -511,8 +511,8 @@
     (Store [8] dst real mem))
 
 // string ops
-(StringPtr (StringMake ptr _)) -> ptr
-(StringLen (StringMake _ len)) -> len
+(StringPtr (StringMake (Const64 <t> [c]) _)) -> (Const64 <t> [c])
+(StringLen (StringMake _ (Const64 <t> [c]))) -> (Const64 <t> [c])
 (ConstString {s}) && config.PtrSize == 4 && s.(string) == "" ->
   (StringMake (ConstNil) (Const32 <config.fe.TypeInt()> [0]))
 (ConstString {s}) && config.PtrSize == 8 && s.(string) == "" ->
@@ -540,9 +540,9 @@
     (Store [config.PtrSize] dst ptr mem))
 
 // slice ops
-(SlicePtr (SliceMake ptr _ _ )) -> ptr
-(SliceLen (SliceMake _ len _)) -> len
-(SliceCap (SliceMake _ _ cap)) -> cap
+(SlicePtr (SliceMake (Const64 <t> [c]) _ _)) -> (Const64 <t> [c])
+(SliceLen (SliceMake _ (Const64 <t> [c]) _)) -> (Const64 <t> [c])
+(SliceCap (SliceMake _ _ (Const64 <t> [c]))) -> (Const64 <t> [c])
 (ConstSlice) && config.PtrSize == 4 ->
   (SliceMake
     (ConstNil <config.fe.TypeBytePtr()>)

src/cmd/compile/internal/ssa/opt.go

@@ -8,3 +8,7 @@ package ssa
 func opt(f *Func) {
 	applyRewrite(f, rewriteBlockgeneric, rewriteValuegeneric)
 }
+
+func dec(f *Func) {
+	applyRewrite(f, rewriteBlockdec, rewriteValuedec)
+}

src/cmd/compile/internal/ssa/rewritedec.go

+// autogenerated from gen/dec.rules: do not edit!
+// generated with: cd gen; go run *.go
+
+package ssa
+
+import "math"
+
+var _ = math.MinInt8 // in case not otherwise used
+func rewriteValuedec(v *Value, config *Config) bool {
+	switch v.Op {
+	case OpSliceCap:
+		return rewriteValuedec_OpSliceCap(v, config)
+	case OpSliceLen:
+		return rewriteValuedec_OpSliceLen(v, config)
+	case OpSlicePtr:
+		return rewriteValuedec_OpSlicePtr(v, config)
+	case OpStringLen:
+		return rewriteValuedec_OpStringLen(v, config)
+	case OpStringPtr:
+		return rewriteValuedec_OpStringPtr(v, config)
+	}
+	return false
+}
+func rewriteValuedec_OpSliceCap(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (SliceCap (SliceMake _ _ cap))
+	// cond:
+	// result: cap
+	for {
+		if v.Args[0].Op != OpSliceMake {
+			break
+		}
+		cap := v.Args[0].Args[2]
+		v.reset(OpCopy)
+		v.Type = cap.Type
+		v.AddArg(cap)
+		return true
+	}
+	return false
+}
+func rewriteValuedec_OpSliceLen(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (SliceLen (SliceMake _ len _))
+	// cond:
+	// result: len
+	for {
+		if v.Args[0].Op != OpSliceMake {
+			break
+		}
+		len := v.Args[0].Args[1]
+		v.reset(OpCopy)
+		v.Type = len.Type
+		v.AddArg(len)
+		return true
+	}
+	return false
+}
+func rewriteValuedec_OpSlicePtr(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (SlicePtr (SliceMake ptr _ _ ))
+	// cond:
+	// result: ptr
+	for {
+		if v.Args[0].Op != OpSliceMake {
+			break
+		}
+		ptr := v.Args[0].Args[0]
+		v.reset(OpCopy)
+		v.Type = ptr.Type
+		v.AddArg(ptr)
+		return true
+	}
+	return false
+}
+func rewriteValuedec_OpStringLen(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (StringLen (StringMake _ len))
+	// cond:
+	// result: len
+	for {
+		if v.Args[0].Op != OpStringMake {
+			break
+		}
+		len := v.Args[0].Args[1]
+		v.reset(OpCopy)
+		v.Type = len.Type
+		v.AddArg(len)
+		return true
+	}
+	return false
+}
+func rewriteValuedec_OpStringPtr(v *Value, config *Config) bool {
+	b := v.Block
+	_ = b
+	// match: (StringPtr (StringMake ptr _))
+	// cond:
+	// result: ptr
+	for {
+		if v.Args[0].Op != OpStringMake {
+			break
+		}
+		ptr := v.Args[0].Args[0]
+		v.reset(OpCopy)
+		v.Type = ptr.Type
+		v.AddArg(ptr)
+		return true
+	}
+	return false
+}
+func rewriteBlockdec(b *Block) bool {
+	switch b.Kind {
+	}
+	return false
+}

src/cmd/compile/internal/ssa/rewritegeneric.go

@@ -6564,17 +6564,21 @@ func rewriteValuegeneric_OpRsh8x8(v *Value, config *Config) bool {
 func rewriteValuegeneric_OpSliceCap(v *Value, config *Config) bool {
 	b := v.Block
 	_ = b
-	// match: (SliceCap (SliceMake _ _ cap))
+	// match: (SliceCap (SliceMake _ _ (Const64 <t> [c])))
 	// cond:
-	// result: cap
+	// result: (Const64 <t> [c])
 	for {
 		if v.Args[0].Op != OpSliceMake {
 			break
 		}
-		cap := v.Args[0].Args[2]
-		v.reset(OpCopy)
-		v.Type = cap.Type
-		v.AddArg(cap)
+		if v.Args[0].Args[2].Op != OpConst64 {
+			break
+		}
+		t := v.Args[0].Args[2].Type
+		c := v.Args[0].Args[2].AuxInt
+		v.reset(OpConst64)
+		v.Type = t
+		v.AuxInt = c
 		return true
 	}
 	return false
@@ -6582,17 +6586,21 @@ func rewriteValuegeneric_OpSliceCap(v *Value, config *Config) bool {
 func rewriteValuegeneric_OpSliceLen(v *Value, config *Config) bool {
 	b := v.Block
 	_ = b
-	// match: (SliceLen (SliceMake _ len _))
+	// match: (SliceLen (SliceMake _ (Const64 <t> [c]) _))
 	// cond:
-	// result: len
+	// result: (Const64 <t> [c])
 	for {
 		if v.Args[0].Op != OpSliceMake {
 			break
 		}
-		len := v.Args[0].Args[1]
-		v.reset(OpCopy)
-		v.Type = len.Type
-		v.AddArg(len)
+		if v.Args[0].Args[1].Op != OpConst64 {
+			break
+		}
+		t := v.Args[0].Args[1].Type
+		c := v.Args[0].Args[1].AuxInt
+		v.reset(OpConst64)
+		v.Type = t
+		v.AuxInt = c
 		return true
 	}
 	return false
@@ -6600,17 +6608,21 @@ func rewriteValuegeneric_OpSliceLen(v *Value, config *Config) bool {
 func rewriteValuegeneric_OpSlicePtr(v *Value, config *Config) bool {
 	b := v.Block
 	_ = b
-	// match: (SlicePtr (SliceMake ptr _ _ ))
+	// match: (SlicePtr (SliceMake (Const64 <t> [c]) _ _))
 	// cond:
-	// result: ptr
+	// result: (Const64 <t> [c])
 	for {
 		if v.Args[0].Op != OpSliceMake {
 			break
 		}
-		ptr := v.Args[0].Args[0]
-		v.reset(OpCopy)
-		v.Type = ptr.Type
-		v.AddArg(ptr)
+		if v.Args[0].Args[0].Op != OpConst64 {
+			break
+		}
+		t := v.Args[0].Args[0].Type
+		c := v.Args[0].Args[0].AuxInt
+		v.reset(OpConst64)
+		v.Type = t
+		v.AuxInt = c
 		return true
 	}
 	return false
@@ -6973,17 +6985,21 @@ func rewriteValuegeneric_OpStore(v *Value, config *Config) bool {
 func rewriteValuegeneric_OpStringLen(v *Value, config *Config) bool {
 	b := v.Block
 	_ = b
-	// match: (StringLen (StringMake _ len))
+	// match: (StringLen (StringMake _ (Const64 <t> [c])))
 	// cond:
-	// result: len
+	// result: (Const64 <t> [c])
 	for {
 		if v.Args[0].Op != OpStringMake {
 			break
 		}
-		len := v.Args[0].Args[1]
-		v.reset(OpCopy)
-		v.Type = len.Type
-		v.AddArg(len)
+		if v.Args[0].Args[1].Op != OpConst64 {
+			break
+		}
+		t := v.Args[0].Args[1].Type
+		c := v.Args[0].Args[1].AuxInt
+		v.reset(OpConst64)
+		v.Type = t
+		v.AuxInt = c
 		return true
 	}
 	return false
@@ -6991,17 +7007,21 @@ func rewriteValuegeneric_OpStringLen(v *Value, config *Config) bool {
 func rewriteValuegeneric_OpStringPtr(v *Value, config *Config) bool {
 	b := v.Block
 	_ = b
-	// match: (StringPtr (StringMake ptr _))
+	// match: (StringPtr (StringMake (Const64 <t> [c]) _))
 	// cond:
-	// result: ptr
+	// result: (Const64 <t> [c])
 	for {
 		if v.Args[0].Op != OpStringMake {
 			break
 		}
-		ptr := v.Args[0].Args[0]
-		v.reset(OpCopy)
-		v.Type = ptr.Type
-		v.AddArg(ptr)
+		if v.Args[0].Args[0].Op != OpConst64 {
+			break
+		}
+		t := v.Args[0].Args[0].Type
+		c := v.Args[0].Args[0].AuxInt
+		v.reset(OpConst64)
+		v.Type = t
+		v.AuxInt = c
 		return true
 	}
 	return false