From: Cherry Zhang <cherryyz@google.com>
Date: Fri, 3 Apr 2020 02:47:29 +0000 (-0400)
Subject: cmd/link: in stack bound check, don't check a call repetitively
X-Git-Tag: go1.15beta1~670
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=e18a5ba0ca142c64aa03c6fb500d69cbbaab1bb6;p=gostls13.git

cmd/link: in stack bound check, don't check a call repetitively

In stack bound check pass, check a call once, not over and over
again. Fix an accidental quadratic behavior...

In particular, switching to the new linker caused MIPS builders
noticeably slower. This CL fixes it.

Change-Id: Idd00c79e80af6278652c92a1d9d7bb2d194e9490
Reviewed-on: https://go-review.googlesource.com/c/go/+/227078
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Austin Clements <austin@google.com>
---

diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index 3f21fc54ef..f7b8e04ddf 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -2360,6 +2360,7 @@ func (sc *stkChk) check(up *chain, depth int) int {
 	relocs := ldr.Relocs(s)
 	var ch1 chain
 	pcsp := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
+	ri := 0
 	for pcsp.Init(info.Pcsp()); !pcsp.Done; pcsp.Next() {
 		// pcsp.value is in effect for [pcsp.pc, pcsp.nextpc).
 
@@ -2370,8 +2371,8 @@ func (sc *stkChk) check(up *chain, depth int) int {
 		}
 
 		// Process calls in this span.
-		for i := 0; i < relocs.Count(); i++ {
-			r := relocs.At2(i)
+		for ; ri < relocs.Count(); ri++ {
+			r := relocs.At2(ri)
 			if uint32(r.Off()) >= pcsp.NextPC {
 				break
 			}