runtime: allocate at desired address when race detector is on

Currently, on all supported platforms, the race detector (LLVM
TSAN) expects the Go heap is at 0xc000000000 - 0xe000000000.
Move the raceenabled condition first, so we always allocate
there.

This means on Linux/ARM64 when race detector is on we will
allocate to 0xc000000000 - 0xe000000000, instead of 0x4000000000.
The old address is meant for 39-bit VMA. But the race detector
only supports 48-bit VMA anyway. So this is fine.

Change-Id: I51ac8eff68297b37c8c651a93145cc94f83a939d
Reviewed-on: https://go-review.googlesource.com/c/go/+/266372
Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 8 insertions, 8 deletions

diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index d0b8c668c3..0563f49d17 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -521,6 +521,14 @@ func mallocinit() {
 		for i := 0x7f; i >= 0; i-- {
 			var p uintptr
 			switch {
+			case raceenabled:
+				// The TSAN runtime requires the heap
+				// to be in the range [0x00c000000000,
+				// 0x00e000000000).
+				p = uintptr(i)<<32 | uintptrMask&(0x00c0<<32)
+				if p >= uintptrMask&0x00e000000000 {
+					continue
+				}
 			case GOARCH == "arm64" && GOOS == "ios":
 				p = uintptr(i)<<40 | uintptrMask&(0x0013<<28)
 			case GOARCH == "arm64":
@@ -532,14 +540,6 @@ func mallocinit() {
 					continue
 				}
 				p = uintptr(i)<<40 | uintptrMask&(0xa0<<52)
-			case raceenabled:
-				// The TSAN runtime requires the heap
-				// to be in the range [0x00c000000000,
-				// 0x00e000000000).
-				p = uintptr(i)<<32 | uintptrMask&(0x00c0<<32)
-				if p >= uintptrMask&0x00e000000000 {
-					continue
-				}
 			default:
 				p = uintptr(i)<<40 | uintptrMask&(0x00c0<<32)
 			}