runtime/cgo: add linux/mips64x cgo support

MIPS N64 ABI passes arguments in registers R4-R11, return value in R2.
R16-R23, R28, R30 and F24-F31 are callee-save. gcc PIC code expects
to be called with indirect call through R25.

Change-Id: I24f582b4b58e1891ba9fd606509990f95cca8051
Reviewed-on: https://go-review.googlesource.com/19805Reviewed-by: Minux Ma <minux@golang.org>

src/runtime/cgo/asm_mips64x.s

+// Copyright 2016 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build mips64 mips64le
+
+#include "textflag.h"
+
+/*
+ * void crosscall2(void (*fn)(void*, int32), void*, int32)
+ * Save registers and call fn with two arguments.
+ */
+TEXT crosscall2(SB),NOSPLIT,$-8
+	/*
+	 * We still need to save all callee save register as before, and then
+	 *  push 2 args for fn (R5 and R6).
+	 * Also note that at procedure entry in gc world, 8(R29) will be the
+	 *  first arg.
+	 */
+	ADDV	$(-8*22), R29
+	MOVV	R5, (8*1)(R29)
+	MOVV	R6, (8*2)(R29)
+	MOVV	R16, (8*3)(R29)
+	MOVV	R17, (8*4)(R29)
+	MOVV	R18, (8*5)(R29)
+	MOVV	R19, (8*6)(R29)
+	MOVV	R20, (8*7)(R29)
+	MOVV	R21, (8*8)(R29)
+	MOVV	R22, (8*9)(R29)
+	MOVV	R23, (8*10)(R29)
+	MOVV	RSB, (8*11)(R29)
+	MOVV	g, (8*12)(R29)
+	MOVV	R31, (8*13)(R29)
+	MOVD	F24, (8*14)(R29)
+	MOVD	F25, (8*15)(R29)
+	MOVD	F26, (8*16)(R29)
+	MOVD	F27, (8*17)(R29)
+	MOVD	F28, (8*18)(R29)
+	MOVD	F29, (8*19)(R29)
+	MOVD	F30, (8*20)(R29)
+	MOVD	F31, (8*21)(R29)
+
+	// Initialize Go ABI environment
+	// prepare SB register = PC & 0xffffffff00000000
+	BGEZAL	R0, 1(PC)
+	SRLV	$32, R31, RSB
+	SLLV	$32, RSB
+	JAL	runtime·reginit(SB)
+	JAL	runtime·load_g(SB)
+	JAL	(R4)
+
+	MOVV	(8*1)(R29), R5
+	MOVV	(8*2)(R29), R6
+	MOVV	(8*3)(R29), R16
+	MOVV	(8*4)(R29), R17
+	MOVV	(8*5)(R29), R18
+	MOVV	(8*6)(R29), R19
+	MOVV	(8*7)(R29), R20
+	MOVV	(8*8)(R29), R21
+	MOVV	(8*9)(R29), R22
+	MOVV	(8*10)(R29), R23
+	MOVV	(8*11)(R29), RSB
+	MOVV	(8*12)(R29), g
+	MOVV	(8*13)(R29), R31
+	MOVD	(8*14)(R29), F24
+	MOVD	(8*15)(R29), F25
+	MOVD	(8*16)(R29), F26
+	MOVD	(8*17)(R29), F27
+	MOVD	(8*18)(R29), F28
+	MOVD	(8*19)(R29), F29
+	MOVD	(8*20)(R29), F30
+	MOVD	(8*21)(R29), F31
+	ADDV	$(8*22), R29
+	RET

src/runtime/cgo/gcc_linux_mips64x.c

+// Copyright 2016 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cgo
+// +build linux
+// +build mips64 mips64le
+
+#include <pthread.h>
+#include <string.h>
+#include <signal.h>
+#include "libcgo.h"
+
+static void *threadentry(void*);
+
+void (*x_cgo_inittls)(void **tlsg, void **tlsbase);
+void (*setg_gcc)(void*);
+
+void
+_cgo_sys_thread_start(ThreadStart *ts)
+{
+	pthread_attr_t attr;
+	sigset_t ign, oset;
+	pthread_t p;
+	size_t size;
+	int err;
+
+	sigfillset(&ign);
+	pthread_sigmask(SIG_SETMASK, &ign, &oset);
+
+	// Not sure why the memset is necessary here,
+	// but without it, we get a bogus stack size
+	// out of pthread_attr_getstacksize.  C'est la Linux.
+	memset(&attr, 0, sizeof attr);
+	pthread_attr_init(&attr);
+	size = 0;
+	pthread_attr_getstacksize(&attr, &size);
+	// Leave stacklo=0 and set stackhi=size; mstack will do the rest.
+	ts->g->stackhi = size;
+	err = pthread_create(&p, &attr, threadentry, ts);
+
+	pthread_sigmask(SIG_SETMASK, &oset, nil);
+
+	if (err != 0) {
+		fatalf("pthread_create failed: %s", strerror(err));
+	}
+}
+
+extern void crosscall1(void (*fn)(void), void (*setg_gcc)(void*), void *g);
+static void*
+threadentry(void *v)
+{
+	ThreadStart ts;
+
+	ts = *(ThreadStart*)v;
+	free(v);
+
+	crosscall1(ts.fn, setg_gcc, (void*)ts.g);
+	return nil;
+}
+
+void
+x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
+{
+	pthread_attr_t attr;
+	size_t size;
+
+	setg_gcc = setg;
+	pthread_attr_init(&attr);
+	pthread_attr_getstacksize(&attr, &size);
+	g->stacklo = (uintptr)&attr - size + 4096;
+	pthread_attr_destroy(&attr);
+
+	if (x_cgo_inittls) {
+		x_cgo_inittls(tlsg, tlsbase);
+	}
+}

src/runtime/cgo/gcc_mips64x.S

+// Copyright 2016 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build mips64 mips64le
+
+/*
+ * void crosscall1(void (*fn)(void), void (*setg_gcc)(void *g), void *g)
+ *
+ * Calling into the gc tool chain, where all registers are caller save.
+ * Called from standard MIPS N64 ABI, where $16-$23, $28, $30, and $f24-$f31
+ * are callee-save, so they must be saved explicitly, along with $31 (LR).
+ */
+.globl crosscall1
+.set noat
+crosscall1:
+	daddiu	$29, $29, -160
+	sd	$31, 0($29)
+	sd	$16, 8($29)
+	sd	$17, 16($29)
+	sd	$18, 24($29)
+	sd	$19, 32($29)
+	sd	$20, 40($29)
+	sd	$21, 48($29)
+	sd	$22, 56($29)
+	sd	$23, 64($29)
+	sd	$28, 72($29)
+	sd	$30, 80($29)
+	sdc1	$f24, 88($29)
+	sdc1	$f25, 96($29)
+	sdc1	$f26, 104($29)
+	sdc1	$f27, 112($29)
+	sdc1	$f28, 120($29)
+	sdc1	$f29, 128($29)
+	sdc1	$f30, 136($29)
+	sdc1	$f31, 144($29)
+
+	dla	$23,_cgo_reginit
+
+	// prepare SB register = pc & 0xffffffff00000000
+	bal	1f
+1:
+	dsrl	$28, $31, 32
+	dsll	$28, $28, 32
+
+	move	$20, $4 // save R4
+	jalr	$23	// call _cgo_reginit, set up Go ABI constant registers
+	move	$1, $6
+	jalr	$5	// call setg_gcc (clobbers R4)
+	jalr	$20	// call fn
+
+	ld	$16, 8($29)
+	ld	$17, 16($29)
+	ld	$18, 24($29)
+	ld	$19, 32($29)
+	ld	$20, 40($29)
+	ld	$21, 48($29)
+	ld	$22, 56($29)
+	ld	$23, 64($29)
+	ld	$28, 72($29)
+	ld	$30, 80($29)
+	ldc1	$f24, 88($29)
+	ldc1	$f25, 96($29)
+	ldc1	$f26, 104($29)
+	ldc1	$f27, 112($29)
+	ldc1	$f28, 120($29)
+	ldc1	$f29, 128($29)
+	ldc1	$f30, 136($29)
+	ldc1	$f31, 144($29)
+	ld	$31, 0($29)
+
+	daddiu	$29, $29, 160
+	jr	$31
+
+.set at
+
+#ifdef __ELF__
+.section .note.GNU-stack,"",%progbits
+#endif