From: Keith Randall <khr@golang.org>
Date: Thu, 25 Feb 2016 19:40:51 +0000 (-0800)
Subject: [dev.ssa] cmd/compile: shrink stack guard
X-Git-Tag: go1.7beta1~1623^2^2~18
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=d3f15ff6bc353d94b7249f33bb030ee1f7ee887e;p=gostls13.git

[dev.ssa] cmd/compile: shrink stack guard

Our stack frame sizes look pretty good now.  Lower the stack
guard from 1024 to 720.
Tip is currently using 720.
We could go lower (to 640 at least) except PPC doesn't like that.

Change-Id: Ie5f96c0e822435638223f1e8a2bd1a1eed68e6aa
Reviewed-on: https://go-review.googlesource.com/19922
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
---

diff --git a/src/cmd/internal/obj/stack.go b/src/cmd/internal/obj/stack.go
index 1a2ee12291..80f6c6c164 100644
--- a/src/cmd/internal/obj/stack.go
+++ b/src/cmd/internal/obj/stack.go
@@ -11,7 +11,7 @@ const (
 	STACKSYSTEM = 0
 	StackSystem = STACKSYSTEM
 	StackBig    = 4096
-	StackGuard  = 1024*stackGuardMultiplier + StackSystem
+	StackGuard  = 720*stackGuardMultiplier + StackSystem
 	StackSmall  = 128
 	StackLimit  = StackGuard - StackSystem - StackSmall
 )
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index ba1a1bb143..81059965d9 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -90,7 +90,7 @@ const (
 
 	// The stack guard is a pointer this many bytes above the
 	// bottom of the stack.
-	_StackGuard = 1024*sys.StackGuardMultiplier + _StackSystem
+	_StackGuard = 720*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
diff --git a/test/nosplit.go b/test/nosplit.go
index 2bf7077808..082fc3b0e6 100644
--- a/test/nosplit.go
+++ b/test/nosplit.go
@@ -302,13 +302,13 @@ TestCases:
 				// Instead of rewriting the test cases above, adjust
 				// the first stack frame to use up the extra bytes.
 				if i == 0 {
-					size += (1024 - 128) - 128
+					size += (720 - 128) - 128
 					// Noopt builds have a larger stackguard.
 					// See ../src/cmd/dist/buildruntime.go:stackGuardMultiplier
 					// This increase is included in obj.StackGuard
 					for _, s := range strings.Split(os.Getenv("GO_GCFLAGS"), " ") {
 						if s == "-N" {
-							size += 1024
+							size += 720
 						}
 					}
 				}