runtime: refactor/fix asmcgocall/asmcgocall_errno
Instead of making asmcgocall call asmcgocall_errno,
make both load args into registers and call a shared
assembly function.
On amd64, this costs 1 word in the asmcgocall_errno path
but saves 3 words in the asmcgocall path, and the latter
is what happens on critical nosplit paths on Windows.
On arm, this fixes build failures: asmcgocall was writing
the arguments for asmcgocall_errno into the wrong
place on the stack. Passing them in registers avoids the
decision entirely.
On 386, this isn't really needed, since the nosplit paths
have twice as many words to work with, but do it for consistency.
Update #8635
Fixes arm build (except GOARM=5).
TBR=iant
CC=golang-codereviews
https://golang.org/cl/134390043
diff --git a/misc/cgo/test/callback.go b/misc/cgo/test/callback.go
index 67d2714..98f653e 100644
--- a/misc/cgo/test/callback.go
+++ b/misc/cgo/test/callback.go
@@ -156,6 +156,7 @@
"runtime.cgocallbackg1",
"runtime.cgocallbackg",
"runtime.cgocallback_gofunc",
+ "asmcgocall",
"runtime.asmcgocall_errno",
"runtime.cgocall_errno",
"test._Cfunc_callback",
@@ -182,8 +183,12 @@
if strings.HasPrefix(fname, "_") {
fname = path.Base(f.Name()[1:])
}
- if fname != name[i] {
- t.Errorf("expected function name %s, got %s", name[i], fname)
+ namei := ""
+ if i < len(name) {
+ namei = name[i]
+ }
+ if fname != namei {
+ t.Errorf("stk[%d] = %q, want %q", i, fname, namei)
}
}
}
diff --git a/src/pkg/runtime/asm_386.s b/src/pkg/runtime/asm_386.s
index 2477726..aafe960 100644
--- a/src/pkg/runtime/asm_386.s
+++ b/src/pkg/runtime/asm_386.s
@@ -680,17 +680,21 @@
// Call fn(arg) on the scheduler stack,
// aligned appropriately for the gcc ABI.
// See cgocall.c for more details.
-TEXT runtime·asmcgocall(SB),NOSPLIT,$12-8
+TEXT runtime·asmcgocall(SB),NOSPLIT,$0-8
MOVL fn+0(FP), AX
MOVL arg+4(FP), BX
- MOVL AX, 0(SP)
- MOVL BX, 4(SP)
- CALL runtime·asmcgocall_errno(SB)
+ CALL asmcgocall<>(SB)
RET
TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-12
MOVL fn+0(FP), AX
MOVL arg+4(FP), BX
+ CALL asmcgocall<>(SB)
+ MOVL AX, ret+8(FP)
+ RET
+
+TEXT asmcgocall<>(SB),NOSPLIT,$0-12
+ // fn in AX, arg in BX
MOVL SP, DX
// Figure out if we need to switch to m->g0 stack.
@@ -720,7 +724,6 @@
MOVL 8(SP), DI
MOVL DI, g(CX)
MOVL 4(SP), SP
- MOVL AX, ret+8(FP)
RET
// cgocallback(void (*fn)(void*), void *frame, uintptr framesize)
diff --git a/src/pkg/runtime/asm_amd64.s b/src/pkg/runtime/asm_amd64.s
index d7e30de..5840b56 100644
--- a/src/pkg/runtime/asm_amd64.s
+++ b/src/pkg/runtime/asm_amd64.s
@@ -764,17 +764,21 @@
// Call fn(arg) on the scheduler stack,
// aligned appropriately for the gcc ABI.
// See cgocall.c for more details.
-TEXT runtime·asmcgocall(SB),NOSPLIT,$24-16
+TEXT runtime·asmcgocall(SB),NOSPLIT,$0-16
MOVQ fn+0(FP), AX
MOVQ arg+8(FP), BX
- MOVQ AX, 0(SP)
- MOVQ BX, 8(SP)
- CALL runtime·asmcgocall_errno(SB)
+ CALL asmcgocall<>(SB)
RET
TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-20
MOVQ fn+0(FP), AX
MOVQ arg+8(FP), BX
+ CALL asmcgocall<>(SB)
+ MOVL AX, ret+16(FP)
+ RET
+
+// asmcgocall common code. fn in AX, arg in BX. returns errno in AX.
+TEXT asmcgocall<>(SB),NOSPLIT,$0-0
MOVQ SP, DX
// Figure out if we need to switch to m->g0 stack.
@@ -813,7 +817,6 @@
MOVQ 48(SP), DI
MOVQ DI, g(CX)
MOVQ 40(SP), SP
- MOVL AX, ret+16(FP)
RET
// cgocallback(void (*fn)(void*), void *frame, uintptr framesize)
diff --git a/src/pkg/runtime/asm_arm.s b/src/pkg/runtime/asm_arm.s
index 26b58cf..49a8632 100644
--- a/src/pkg/runtime/asm_arm.s
+++ b/src/pkg/runtime/asm_arm.s
@@ -493,17 +493,21 @@
// Call fn(arg) on the scheduler stack,
// aligned appropriately for the gcc ABI.
// See cgocall.c for more details.
-TEXT runtime·asmcgocall(SB),NOSPLIT,$12-8
+TEXT runtime·asmcgocall(SB),NOSPLIT,$0-8
MOVW fn+0(FP), R1
- MOVW arg+4(FP), R2
- MOVW R1, 0(R13)
- MOVW R2, 4(R13)
- BL runtime·asmcgocall_errno(SB)
+ MOVW arg+4(FP), R0
+ BL asmcgocall<>(SB)
RET
TEXT runtime·asmcgocall_errno(SB),NOSPLIT,$0-12
MOVW fn+0(FP), R1
MOVW arg+4(FP), R0
+ BL asmcgocall<>(SB)
+ MOVW R0, ret+8(FP)
+ RET
+
+TEXT asmcgocall<>(SB),NOSPLIT,$0-0
+ // fn in R1, arg in R0.
MOVW R13, R2
MOVW g, R5
@@ -529,7 +533,6 @@
// Restore registers, g, stack pointer.
MOVW 20(R13), g
MOVW 16(R13), R13
- MOVW R0, ret+8(FP)
RET
// cgocallback(void (*fn)(void*), void *frame, uintptr framesize)
