runtime: unify amd64 -buildmode=exe entry point code

All of the amd64 entry point code is the same except for Plan 9.
Unify it all into asm_amd64.s.

Change-Id: Id47ce3a7bb2bb0fd48f326a2d88ed18b17dee456
Reviewed-on: https://go-review.googlesource.com/69292
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/asm_amd64.s

@@ -7,6 +7,21 @@
 #include "funcdata.h"
 #include "textflag.h"
 
+// _rt0_amd64 is common startup code for most amd64 systems when using
+// internal linking. This is the entry point for the program from the
+// kernel for an ordinary -buildmode=exe program. The stack holds the
+// number of arguments and the C-style argv.
+TEXT _rt0_amd64(SB),NOSPLIT,$-8
+	MOVQ	0(SP), DI	// argc
+	LEAQ	8(SP), SI	// argv
+	JMP	runtime·rt0_go(SB)
+
+// main is common startup code for most amd64 systems when using
+// external linking. The C startup code will call the symbol "main"
+// passing argc and argv in the usual C ABI registers DI and SI.
+TEXT main(SB),NOSPLIT,$-8
+	JMP	runtime·rt0_go(SB)
+
 TEXT runtime·rt0_go(SB),NOSPLIT,$0
 	// copy arguments forward on an even stack
 	MOVQ	DI, AX		// argc

src/runtime/rt0_android_amd64.s

@@ -5,10 +5,7 @@
 #include "textflag.h"
 
 TEXT _rt0_amd64_android(SB),NOSPLIT,$-8
-	MOVQ	0(SP), DI // argc
-	LEAQ	8(SP), SI // argv
-	MOVQ	$main(SB), AX
-	JMP	AX
+	JMP	_rt0_amd64(SB)
 
 TEXT _rt0_amd64_android_lib(SB),NOSPLIT,$0
 	MOVQ	$1, DI // argc

src/runtime/rt0_darwin_amd64.s

@@ -5,10 +5,7 @@
 #include "textflag.h"
 
 TEXT _rt0_amd64_darwin(SB),NOSPLIT,$-8
-	LEAQ	8(SP), SI // argv
-	MOVQ	0(SP), DI // argc
-	MOVQ	$main(SB), AX
-	JMP	AX
+	JMP	_rt0_amd64(SB)
 
 // When linking with -shared, this symbol is called when the shared library
 // is loaded.
@@ -73,7 +70,3 @@ DATA _rt0_amd64_darwin_lib_argc<>(SB)/8, $0
 GLOBL _rt0_amd64_darwin_lib_argc<>(SB),NOPTR, $8
 DATA _rt0_amd64_darwin_lib_argv<>(SB)/8, $0
 GLOBL _rt0_amd64_darwin_lib_argv<>(SB),NOPTR, $8
-
-TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$runtime·rt0_go(SB), AX
-	JMP	AX

src/runtime/rt0_dragonfly_amd64.s

@@ -5,11 +5,4 @@
 #include "textflag.h"
 
 TEXT _rt0_amd64_dragonfly(SB),NOSPLIT,$-8
-	LEAQ	8(DI), SI // argv
-	MOVQ	0(DI), DI // argc
-	MOVQ	$main(SB), AX
-	JMP	AX
-
-TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$runtime·rt0_go(SB), AX
-	JMP	AX
+	JMP	_rt0_amd64(SB)

src/runtime/rt0_freebsd_amd64.s

@@ -4,12 +4,8 @@
 
 #include "textflag.h"
 
+// On FreeBSD argc/argv are passed in DI, not SP, so we can't use _rt0_amd64.
 TEXT _rt0_amd64_freebsd(SB),NOSPLIT,$-8
 	LEAQ	8(DI), SI // argv
 	MOVQ	0(DI), DI // argc
-	MOVQ	$main(SB), AX
-	JMP	AX
-
-TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$runtime·rt0_go(SB), AX
-	JMP	AX
+	JMP	runtime·rt0_go(SB)

src/runtime/rt0_linux_amd64.s

@@ -5,10 +5,7 @@
 #include "textflag.h"
 
 TEXT _rt0_amd64_linux(SB),NOSPLIT,$-8
-	LEAQ	8(SP), SI // argv
-	MOVQ	0(SP), DI // argc
-	MOVQ	$main(SB), AX
-	JMP	AX
+	JMP	_rt0_amd64(SB)
 
 // When building with -buildmode=c-shared, this symbol is called when the shared
 // library is loaded.
@@ -68,7 +65,3 @@ DATA _rt0_amd64_linux_lib_argc<>(SB)/8, $0
 GLOBL _rt0_amd64_linux_lib_argc<>(SB),NOPTR, $8
 DATA _rt0_amd64_linux_lib_argv<>(SB)/8, $0
 GLOBL _rt0_amd64_linux_lib_argv<>(SB),NOPTR, $8
-
-TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$runtime·rt0_go(SB), AX
-	JMP	AX

src/runtime/rt0_netbsd_amd64.s

@@ -5,11 +5,4 @@
 #include "textflag.h"
 
 TEXT _rt0_amd64_netbsd(SB),NOSPLIT,$-8
-	LEAQ	8(SP), SI // argv
-	MOVQ	0(SP), DI // argc
-	MOVQ	$main(SB), AX
-	JMP	AX
-
-TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$runtime·rt0_go(SB), AX
-	JMP	AX
+	JMP	_rt0_amd64(SB)

src/runtime/rt0_openbsd_amd64.s

@@ -5,11 +5,4 @@
 #include "textflag.h"
 
 TEXT _rt0_amd64_openbsd(SB),NOSPLIT,$-8
-	LEAQ	8(SP), SI // argv
-	MOVQ	0(SP), DI // argc
-	MOVQ	$main(SB), AX
-	JMP	AX
-
-TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$runtime·rt0_go(SB), AX
-	JMP	AX
+	JMP	_rt0_amd64(SB)

src/runtime/rt0_solaris_amd64.s

@@ -5,11 +5,4 @@
 #include "textflag.h"
 
 TEXT _rt0_amd64_solaris(SB),NOSPLIT,$-8
-	LEAQ	8(SP), SI // argv
-	MOVQ	0(SP), DI // argc
-	MOVQ	$main(SB), AX
-	JMP	AX
-
-TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$runtime·rt0_go(SB), AX
-	JMP	AX
+	JMP	_rt0_amd64(SB)

src/runtime/rt0_windows_amd64.s

@@ -7,10 +7,7 @@
 #include "textflag.h"
 
 TEXT _rt0_amd64_windows(SB),NOSPLIT,$-8
-	LEAQ	8(SP), SI // argv
-	MOVQ	0(SP), DI // argc
-	MOVQ	$main(SB), AX
-	JMP	AX
+	JMP	_rt0_amd64(SB)
 
 // When building with -buildmode=(c-shared or c-archive), this
 // symbol is called. For dynamic libraries it is called when the
@@ -42,7 +39,3 @@ TEXT _rt0_amd64_windows_lib_go(SB),NOSPLIT,$0
 	MOVQ	$0, SI
 	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX
-
-TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$runtime·rt0_go(SB), AX
-	JMP	AX