runtime: Use getcontext, not setjmp, to save regs for GC.

From-SVN: r187777

libgo/runtime/proc.c

@@ -1239,9 +1239,7 @@ runtime_entersyscall(void)
 
 	// Save the registers in the g structure so that any pointers
 	// held in registers will be seen by the garbage collector.
-	// We could use getcontext here, but setjmp is more efficient
-	// because it doesn't need to save the signal mask.
-	setjmp(g->gcregs);
+	getcontext(&g->gcregs);
 
 	g->status = Gsyscall;
 
@@ -1299,7 +1297,7 @@ runtime_exitsyscall(void)
 		gp->gcstack = nil;
 #endif
 		gp->gcnext_sp = nil;
-		runtime_memclr(gp->gcregs, sizeof gp->gcregs);
+		runtime_memclr(&gp->gcregs, sizeof gp->gcregs);
 
 		if(m->profilehz > 0)
 			runtime_setprof(true);
@@ -1328,7 +1326,7 @@ runtime_exitsyscall(void)
 	gp->gcstack = nil;
 #endif
 	gp->gcnext_sp = nil;
-	runtime_memclr(gp->gcregs, sizeof gp->gcregs);
+	runtime_memclr(&gp->gcregs, sizeof gp->gcregs);
 }
 
 // Allocate a new g, with a stack big enough for stacksize bytes.

libgo/runtime/runtime.h

@@ -7,7 +7,6 @@
 #include "config.h"
 
 #include "go-assert.h"
-#include <setjmp.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -128,7 +127,7 @@ struct	G
 	void*	gcnext_segment;
 	void*	gcnext_sp;
 	void*	gcinitial_sp;
-	jmp_buf	gcregs;
+	ucontext_t gcregs;
 	byte*	entry;		// initial function
 	G*	alllink;	// on allg
 	void*	param;		// passed parameter on wakeup