runtime: clean up windows a bit

Document the various hard-coded architecture checks
or remove them in favor of more general checks.
This should be a no-op now but will make the arm64 port
have fewer diffs.

This CL is part of a stack adding windows/arm64
support (#36439), intended to land in the Go 1.17 cycle.
This CL is, however, not windows/arm64-specific.
It is cleanup meant to make the port (and future ports) easier.

Change-Id: Ifd6b19e44e8c9ca4a0d2590f314928ce235821b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/288813
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

1 files changed, 6 insertions, 7 deletions

diff --git a/src/runtime/signal_windows.go b/src/runtime/signal_windows.go
index 18834b0ec5..cb1fbe9f81 100644
--- a/src/runtime/signal_windows.go
+++ b/src/runtime/signal_windows.go
@@ -5,6 +5,7 @@
 package runtime
 
 import (
+	"runtime/internal/sys"
 	"unsafe"
 )
 
@@ -132,16 +133,14 @@ func exceptionhandler(info *exceptionrecord, r *context, gp *g) int32 {
 	// overwrite the PC. (See issue #35773)
 	if r.ip() != 0 && r.ip() != funcPC(asyncPreempt) {
 		sp := unsafe.Pointer(r.sp())
-		sp = add(sp, ^(unsafe.Sizeof(uintptr(0)) - 1)) // sp--
+		delta := uintptr(sys.StackAlign)
+		sp = add(sp, -delta)
 		r.set_sp(uintptr(sp))
-		switch GOARCH {
-		default:
-			panic("unsupported architecture")
-		case "386", "amd64":
-			*((*uintptr)(sp)) = r.ip()
-		case "arm":
+		if usesLR {
 			*((*uintptr)(sp)) = r.lr()
 			r.set_lr(r.ip())
+		} else {
+			*((*uintptr)(sp)) = r.ip()
 		}
 	}
 	r.set_ip(funcPC(sigpanic))