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, 2 insertions, 1 deletions

diff --git a/src/runtime/syscall_windows.go b/src/runtime/syscall_windows.go
index add40bb0b3..6052cc333c 100644
--- a/src/runtime/syscall_windows.go
+++ b/src/runtime/syscall_windows.go
@@ -116,13 +116,14 @@ func compileCallback(fn eface, cdecl bool) (code uintptr) {
 			// registers and the stack.
 			panic("compileCallback: argument size is larger than uintptr")
 		}
-		if k := t.kind & kindMask; (GOARCH == "amd64" || GOARCH == "arm") && (k == kindFloat32 || k == kindFloat64) {
+		if k := t.kind & kindMask; GOARCH != "386" && (k == kindFloat32 || k == kindFloat64) {
 			// In fastcall, floating-point arguments in
 			// the first four positions are passed in
 			// floating-point registers, which we don't
 			// currently spill. arm passes floating-point
 			// arguments in VFP registers, which we also
 			// don't support.
+			// So basically we only support 386.
 			panic("compileCallback: float arguments not supported")
 		}