internal/abi, runtime, cmd: merge StackSmall, StackBig consts into internal/abi

For #59670.

Change-Id: I91448363be2fc678964ce119d85cd5fae34a14da
Reviewed-on: https://go-review.googlesource.com/c/go/+/486975
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
Auto-Submit: Austin Clements <austin@google.com>

src/cmd/internal/obj/arm/obj5.go

@@ -709,7 +709,7 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 	// unnecessarily. See issue #35470.
 	p = c.ctxt.StartUnsafePoint(p, c.newprog)
 
-	if framesize <= objabi.StackSmall {
+	if framesize <= abi.StackSmall {
 		// small stack: SP < stackguard
 		//	CMP	stackguard, SP
 		p = obj.Appendp(p, c.newprog)
@@ -718,7 +718,7 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = REG_R1
 		p.Reg = REGSP
-	} else if framesize <= objabi.StackBig {
+	} else if framesize <= abi.StackBig {
 		// large stack: SP-framesize < stackguard-StackSmall
 		//	MOVW $-(framesize-StackSmall)(SP), R2
 		//	CMP stackguard, R2
@@ -727,7 +727,7 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p.As = AMOVW
 		p.From.Type = obj.TYPE_ADDR
 		p.From.Reg = REGSP
-		p.From.Offset = -(int64(framesize) - objabi.StackSmall)
+		p.From.Offset = -(int64(framesize) - abi.StackSmall)
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REG_R2
 
@@ -754,7 +754,7 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p.As = ASUB
 		p.Scond = C_SBIT
 		p.From.Type = obj.TYPE_CONST
-		p.From.Offset = int64(framesize) - objabi.StackSmall
+		p.From.Offset = int64(framesize) - abi.StackSmall
 		p.Reg = REGSP
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REG_R2

src/cmd/internal/obj/arm64/obj7.go

@@ -170,7 +170,7 @@ func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 	p = c.ctxt.StartUnsafePoint(p, c.newprog)
 
 	q := (*obj.Prog)(nil)
-	if framesize <= objabi.StackSmall {
+	if framesize <= abi.StackSmall {
 		// small stack: SP < stackguard
 		//	CMP	stackguard, SP
 
@@ -179,7 +179,7 @@ func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = REGRT1
 		p.Reg = REGSP
-	} else if framesize <= objabi.StackBig {
+	} else if framesize <= abi.StackBig {
 		// large stack: SP-framesize < stackguard-StackSmall
 		//	SUB	$(framesize-StackSmall), SP, RT2
 		//	CMP	stackguard, RT2
@@ -187,7 +187,7 @@ func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 
 		p.As = ASUB
 		p.From.Type = obj.TYPE_CONST
-		p.From.Offset = int64(framesize) - objabi.StackSmall
+		p.From.Offset = int64(framesize) - abi.StackSmall
 		p.Reg = REGSP
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REGRT2
@@ -213,7 +213,7 @@ func (c *ctxt7) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p = obj.Appendp(p, c.newprog)
 		p.As = ASUBS
 		p.From.Type = obj.TYPE_CONST
-		p.From.Offset = int64(framesize) - objabi.StackSmall
+		p.From.Offset = int64(framesize) - abi.StackSmall
 		p.Reg = REGSP
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REGRT2
@@ -583,7 +583,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 				}
 			}
 
-			if p.Mark&LEAF != 0 && c.autosize < objabi.StackSmall {
+			if p.Mark&LEAF != 0 && c.autosize < abi.StackSmall {
 				// A leaf function with a small stack can be marked
 				// NOSPLIT, avoiding a stack check.
 				p.From.Sym.Set(obj.AttrNoSplit, true)

src/cmd/internal/obj/loong64/obj.go

@@ -6,7 +6,6 @@ package loong64
 
 import (
 	"cmd/internal/obj"
-	"cmd/internal/objabi"
 	"cmd/internal/sys"
 	"internal/abi"
 	"log"
@@ -594,7 +593,7 @@ func (c *ctxt0) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 	p = c.ctxt.StartUnsafePoint(p, c.newprog)
 
 	var q *obj.Prog
-	if framesize <= objabi.StackSmall {
+	if framesize <= abi.StackSmall {
 		// small stack: SP < stackguard
 		//	AGTU	SP, stackguard, R19
 		p = obj.Appendp(p, c.newprog)
@@ -607,8 +606,8 @@ func (c *ctxt0) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p.To.Reg = REG_R19
 	} else {
 		// large stack: SP-framesize < stackguard-StackSmall
-		offset := int64(framesize) - objabi.StackSmall
+		offset := int64(framesize) - abi.StackSmall
-		if framesize > objabi.StackBig {
+		if framesize > abi.StackBig {
 			// Such a large stack we need to protect against underflow.
 			// The runtime guarantees SP > objabi.StackBig, but
 			// framesize is large enough that SP-framesize may

src/cmd/internal/obj/mips/obj0.go

@@ -31,7 +31,6 @@ package mips
 
 import (
 	"cmd/internal/obj"
-	"cmd/internal/objabi"
 	"cmd/internal/sys"
 	"encoding/binary"
 	"fmt"
@@ -775,7 +774,7 @@ func (c *ctxt0) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 	p = c.ctxt.StartUnsafePoint(p, c.newprog)
 
 	var q *obj.Prog
-	if framesize <= objabi.StackSmall {
+	if framesize <= abi.StackSmall {
 		// small stack: SP < stackguard
 		//	AGTU	SP, stackguard, R1
 		p = obj.Appendp(p, c.newprog)
@@ -788,8 +787,8 @@ func (c *ctxt0) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p.To.Reg = REG_R1
 	} else {
 		// large stack: SP-framesize < stackguard-StackSmall
-		offset := int64(framesize) - objabi.StackSmall
+		offset := int64(framesize) - abi.StackSmall
-		if framesize > objabi.StackBig {
+		if framesize > abi.StackBig {
 			// Such a large stack we need to protect against underflow.
 			// The runtime guarantees SP > objabi.StackBig, but
 			// framesize is large enough that SP-framesize may

src/cmd/internal/obj/ppc64/obj9.go

@@ -633,7 +633,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 				autosize += int32(c.ctxt.Arch.FixedFrameSize)
 			}
 
-			if p.Mark&LEAF != 0 && autosize < objabi.StackSmall {
+			if p.Mark&LEAF != 0 && autosize < abi.StackSmall {
 				// A leaf function with a small stack can be marked
 				// NOSPLIT, avoiding a stack check.
 				p.From.Sym.Set(obj.AttrNoSplit, true)
@@ -1178,7 +1178,7 @@ func (c *ctxt9) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 	p = c.ctxt.StartUnsafePoint(p, c.newprog)
 
 	var q *obj.Prog
-	if framesize <= objabi.StackSmall {
+	if framesize <= abi.StackSmall {
 		// small stack: SP < stackguard
 		//	CMP	stackguard, SP
 		p = obj.Appendp(p, c.newprog)
@@ -1190,8 +1190,8 @@ func (c *ctxt9) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p.To.Reg = REGSP
 	} else {
 		// large stack: SP-framesize < stackguard-StackSmall
-		offset := int64(framesize) - objabi.StackSmall
+		offset := int64(framesize) - abi.StackSmall
-		if framesize > objabi.StackBig {
+		if framesize > abi.StackBig {
 			// Such a large stack we need to protect against underflow.
 			// The runtime guarantees SP > objabi.StackBig, but
 			// framesize is large enough that SP-framesize may

src/cmd/internal/obj/riscv/obj.go

@@ -829,7 +829,7 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, cursym *obj.LSym, newprog obj.ProgA
 
 	var to_done, to_more *obj.Prog
 
-	if framesize <= objabi.StackSmall {
+	if framesize <= abi.StackSmall {
 		// small stack
 		//	// if SP > stackguard { goto done }
 		//	BLTU	stackguard, SP, done
@@ -842,8 +842,8 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, cursym *obj.LSym, newprog obj.ProgA
 		to_done = p
 	} else {
 		// large stack: SP-framesize < stackguard-StackSmall
-		offset := int64(framesize) - objabi.StackSmall
+		offset := int64(framesize) - abi.StackSmall
-		if framesize > objabi.StackBig {
+		if framesize > abi.StackBig {
 			// Such a large stack we need to protect against underflow.
 			// The runtime guarantees SP > objabi.StackBig, but
 			// framesize is large enough that SP-framesize may

src/cmd/internal/obj/s390x/objz.go

@@ -314,7 +314,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 				autosize += int32(c.ctxt.Arch.FixedFrameSize)
 			}
 
-			if p.Mark&LEAF != 0 && autosize < objabi.StackSmall {
+			if p.Mark&LEAF != 0 && autosize < abi.StackSmall {
 				// A leaf function with a small stack can be marked
 				// NOSPLIT, avoiding a stack check.
 				p.From.Sym.Set(obj.AttrNoSplit, true)
@@ -663,7 +663,7 @@ func (c *ctxtz) stacksplitPre(p *obj.Prog, framesize int32) (pPre, pPreempt, pCh
 	// unnecessarily. See issue #35470.
 	p = c.ctxt.StartUnsafePoint(p, c.newprog)
 
-	if framesize <= objabi.StackSmall {
+	if framesize <= abi.StackSmall {
 		// small stack: SP < stackguard
 		//	CMPUBGE	stackguard, SP, label-of-call-to-morestack
 
@@ -679,8 +679,8 @@ func (c *ctxtz) stacksplitPre(p *obj.Prog, framesize int32) (pPre, pPreempt, pCh
 
 	// large stack: SP-framesize < stackguard-StackSmall
 
-	offset := int64(framesize) - objabi.StackSmall
+	offset := int64(framesize) - abi.StackSmall
-	if framesize > objabi.StackBig {
+	if framesize > abi.StackBig {
 		// Such a large stack we need to protect against underflow.
 		// The runtime guarantees SP > objabi.StackBig, but
 		// framesize is large enough that SP-framesize may

src/cmd/internal/obj/wasm/wasmobj.go

@@ -11,6 +11,7 @@ import (
 	"cmd/internal/sys"
 	"encoding/binary"
 	"fmt"
+	"internal/abi"
 	"io"
 	"math"
 )
@@ -472,7 +473,7 @@ func preprocess(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
 	if needMoreStack {
 		p := pMorestack
 
-		if framesize <= objabi.StackSmall {
+		if framesize <= abi.StackSmall {
 			// small stack: SP <= stackguard
 			// Get SP
 			// Get g
@@ -500,7 +501,7 @@ func preprocess(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
 			p = appendp(p, AGet, regAddr(REGG))
 			p = appendp(p, AI32WrapI64)
 			p = appendp(p, AI32Load, constAddr(2*int64(ctxt.Arch.PtrSize))) // G.stackguard0
-			p = appendp(p, AI32Const, constAddr(framesize-objabi.StackSmall))
+			p = appendp(p, AI32Const, constAddr(framesize-abi.StackSmall))
 			p = appendp(p, AI32Add)
 			p = appendp(p, AI32LeU)
 		}

src/cmd/internal/obj/x86/obj6.go

@@ -642,7 +642,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 	}
 
 	// TODO(rsc): Remove 'ctxt.Arch.Family == sys.AMD64 &&'.
-	if ctxt.Arch.Family == sys.AMD64 && autoffset < objabi.StackSmall && !p.From.Sym.NoSplit() {
+	if ctxt.Arch.Family == sys.AMD64 && autoffset < abi.StackSmall && !p.From.Sym.NoSplit() {
 		leaf := true
 	LeafSearch:
 		for q := p; q != nil; q = q.Link {
@@ -656,7 +656,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 				}
 				fallthrough
 			case obj.ADUFFCOPY, obj.ADUFFZERO:
-				if autoffset >= objabi.StackSmall-8 {
+				if autoffset >= abi.StackSmall-8 {
 					leaf = false
 					break LeafSearch
 				}
@@ -1088,7 +1088,7 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
 	p, rg = loadG(ctxt, cursym, p, newprog)
 
 	var q1 *obj.Prog
-	if framesize <= objabi.StackSmall {
+	if framesize <= abi.StackSmall {
 		// small stack: SP <= stackguard
 		//	CMPQ SP, stackguard
 		p = obj.Appendp(p, newprog)
@@ -1108,7 +1108,7 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
 		// cleared, but we'll still call morestack, which will double the stack
 		// unnecessarily. See issue #35470.
 		p = ctxt.StartUnsafePoint(p, newprog)
-	} else if framesize <= objabi.StackBig {
+	} else if framesize <= abi.StackBig {
 		// large stack: SP-framesize <= stackguard-StackSmall
 		//	LEAQ -xxx(SP), tmp
 		//	CMPQ tmp, stackguard
@@ -1117,7 +1117,7 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
 		p.As = lea
 		p.From.Type = obj.TYPE_MEM
 		p.From.Reg = REG_SP
-		p.From.Offset = -(int64(framesize) - objabi.StackSmall)
+		p.From.Offset = -(int64(framesize) - abi.StackSmall)
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = tmp
 
@@ -1160,7 +1160,7 @@ func stacksplit(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, newprog obj.ProgA
 		p = obj.Appendp(p, newprog)
 		p.As = sub
 		p.From.Type = obj.TYPE_CONST
-		p.From.Offset = int64(framesize) - objabi.StackSmall
+		p.From.Offset = int64(framesize) - abi.StackSmall
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = tmp
 

src/cmd/internal/objabi/stack.go

@@ -4,21 +4,22 @@
 
 package objabi
 
-import "internal/buildcfg"
+import (
+	"internal/abi"
+	"internal/buildcfg"
+)
 
 // For the linkers. Must match Go definitions.
 
 const (
 	STACKSYSTEM = 0
 	StackSystem = STACKSYSTEM
-	StackBig    = 4096
-	StackSmall  = 128
 )
 
 func StackLimit(race bool) int {
 	// This arithmetic must match that in runtime/stack.go:{_StackGuard,_StackLimit}.
 	stackGuard := 928*stackGuardMultiplier(race) + StackSystem
-	stackLimit := stackGuard - StackSystem - StackSmall
+	stackLimit := stackGuard - StackSystem - abi.StackSmall
 	return stackLimit
 }
 

src/internal/abi/stack.go

@@ -0,0 +1,25 @@
+// Copyright 2023 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 abi
+
+const (
+	// We have three different sequences for stack bounds checks, depending on
+	// whether the stack frame of a function is small, big, or huge.
+
+	// After a stack split check the SP is allowed to be StackSmall bytes below
+	// the stack guard.
+	//
+	// Functions that need frames <= StackSmall can perform the stack check
+	// using a single comparison directly between the stack guard and the SP
+	// because we ensure that StackSmall bytes of stack space are available
+	// beyond the stack guard.
+	StackSmall = 128
+
+	// Functions that need frames <= StackBig can assume that neither
+	// SP-framesize nor stackGuard-StackSmall will underflow, and thus use a
+	// more efficient check. In order to ensure this, StackBig must be <= the
+	// size of the unmapped space at zero.
+	StackBig = 4096
+)

src/runtime/stack.go

@@ -85,13 +85,6 @@ const (
 	_FixedStack6 = _FixedStack5 | (_FixedStack5 >> 16)
 	_FixedStack  = _FixedStack6 + 1
 
-	// Functions that need frames bigger than this use an extra
-	// instruction to do the stack split check, to avoid overflow
-	// in case SP - framesize wraps below zero.
-	// This value can be no bigger than the size of the unmapped
-	// space at zero.
-	_StackBig = 4096
-
 	// The stack guard is a pointer this many bytes above the
 	// bottom of the stack.
 	//
@@ -101,15 +94,10 @@ const (
 	// This arithmetic must match that in cmd/internal/objabi/stack.go:StackLimit.
 	_StackGuard = 928*sys.StackGuardMultiplier + _StackSystem
 
-	// After a stack split check the SP is allowed to be this
-	// many bytes below the stack guard. This saves an instruction
-	// in the checking sequence for tiny frames.
-	_StackSmall = 128
-
 	// The maximum number of bytes that a chain of NOSPLIT
 	// functions can use.
 	// This arithmetic must match that in cmd/internal/objabi/stack.go:StackLimit.
-	_StackLimit = _StackGuard - _StackSystem - _StackSmall
+	_StackLimit = _StackGuard - _StackSystem - abi.StackSmall
 )
 
 const (