From: Keith Randall <khr@golang.org>
Date: Wed, 3 Feb 2021 20:25:46 +0000 (-0800)
Subject: runtime: use BX instead of R15 in race detector
X-Git-Tag: go1.17beta1~1415
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=a4dac8bd22;p=gostls13.git

runtime: use BX instead of R15 in race detector

If the race detector were runnable in dynamic linking mode,
then R15 would get clobbered. I don't think it is, so maybe
not a problem, but can't hurt to clean it up.

It also lets CL 283474 pass cleanly when checking the whole stdlib
(together with CL 288452).

Change-Id: I5a5021ecc7e7b8bed1cd3a7067c39b24c09e0783
Reviewed-on: https://go-review.googlesource.com/c/go/+/289270
Trust: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
---

diff --git a/src/runtime/race_amd64.s b/src/runtime/race_amd64.s
index c3b7bbfbfe..e10c21c7f3 100644
--- a/src/runtime/race_amd64.s
+++ b/src/runtime/race_amd64.s
@@ -184,7 +184,7 @@ TEXT	runtime·racefuncenter(SB), NOSPLIT, $0-8
 // Common code for racefuncenter/racefuncenterfp
 // R11 = caller's return address
 TEXT	racefuncenter<>(SB), NOSPLIT, $0-0
-	MOVQ	DX, R15		// save function entry context (for closures)
+	MOVQ	DX, BX		// save function entry context (for closures)
 #ifndef GOEXPERIMENT_REGABI
 	get_tls(R12)
 	MOVQ	g(R12), R14
@@ -193,9 +193,9 @@ TEXT	racefuncenter<>(SB), NOSPLIT, $0-0
 	MOVQ	R11, RARG1
 	// void __tsan_func_enter(ThreadState *thr, void *pc);
 	MOVQ	$__tsan_func_enter(SB), AX
-	// racecall<> preserves R15
+	// racecall<> preserves BX
 	CALL	racecall<>(SB)
-	MOVQ	R15, DX	// restore function entry context
+	MOVQ	BX, DX	// restore function entry context
 	RET
 
 // func runtime·racefuncexit()
@@ -376,7 +376,7 @@ racecallatomic_ignore:
 	// Addr is outside the good range.
 	// Call __tsan_go_ignore_sync_begin to ignore synchronization during the atomic op.
 	// An attempt to synchronize on the address would cause crash.
-	MOVQ	AX, R15	// remember the original function
+	MOVQ	AX, BX	// remember the original function
 	MOVQ	$__tsan_go_ignore_sync_begin(SB), AX
 #ifndef GOEXPERIMENT_REGABI
 	get_tls(R12)
@@ -384,7 +384,7 @@ racecallatomic_ignore:
 #endif
 	MOVQ	g_racectx(R14), RARG0	// goroutine context
 	CALL	racecall<>(SB)
-	MOVQ	R15, AX	// restore the original function
+	MOVQ	BX, AX	// restore the original function
 	// Call the atomic function.
 	MOVQ	g_racectx(R14), RARG0	// goroutine context
 	MOVQ	8(SP), RARG1	// caller pc