libtf: optimize x86 fiber switching

by letting gcc figure out better how to represent stack pointers.
also uses labels to make the code more readable.

2 files changed, 25 insertions, 16 deletions

diff --git a/src/fiber.c b/src/fiber.c
index 6ddde1b..a7cb6bd 100644
--- a/src/fiber.c
+++ b/src/fiber.c
@@ -225,7 +225,7 @@ int tf_schedule(void)
 	if (unlikely(f->timeout_change)) {
 		if (f->timeout_change & TF_TIMEOUT_CHANGE_NEW_VALUE) {
 			if (tf_mtime_diff(f->timeout, tf_mtime()) <= 0) {
-				f->timeout_change = TF_TIMEOUT_CHANGE;
+				f->timeout_change = TF_TIMEOUT_CHANGE_NEEDED;
 				return TF_WAKEUP_TIMEOUT;
 			}
 			tf_heap_change(&f->heap_node, &sched->heap, f->timeout);
diff --git a/src/uctx.h b/src/uctx.h
index 03750e9..541fcf9 100644
--- a/src/uctx.h
+++ b/src/uctx.h
@@ -32,10 +32,32 @@ struct tf_uctx {
 
 #if defined(__i386__)
 
+#define switch_fiber(prev, next)			\
+	do {						\
+		unsigned eax, ebx, ecx, edx, esi, edi;	\
+		__asm__ __volatile__ (			\
+		"push	%%ebp				\n" \
+		"call	1f				\n" \
+		"1:					\n" \
+		"addl	$2f-1b, (%%esp)			\n" \
+		"movl	%%esp, %[prev_sp]		\n" \
+		"movl	%[next_sp], %%esp		\n" \
+		"ret					\n" \
+		"2:					\n" \
+		"pop	%%ebp				\n" \
+		: [prev_sp] "=m"(prev->current_sp),	\
+		  "=a"(eax), "=b"(ebx), "=c"(ecx),	\
+		  "=d"(edx), "=S"(esi), "=D"(edi)	\
+		: [next_sp] "m"(next->current_sp)	\
+		: "memory", "cc");			\
+	} while (0)
+
 #define STACK_GROWS_UP
 
 #else
-#error Your architecture is not supported. Send email to timo.teras@iki.fi.
+
+#error Your architecture is not supported. Contact timo.teras@iki.fi.
+
 #endif
 
 #if defined(STACK_GROWS_UP)
@@ -108,19 +130,6 @@ void tf_uctx_destroy(struct tf_fiber *fiber)
 	free(uctx->alloc);
 }
 
-#define switch_fiber(oldspptr, newsp)		\
-	__asm__ __volatile__ (			\
-		"push	%%ebp		;"	\
-		"call	.+5		;"	\
-		"add	$0x9,(%%esp)	;"	\
-		"mov	%%esp, (%0)	;"	\
-		"mov	%1, %%esp	;"	\
-		"ret			;"	\
-		"pop	%%ebp"			\
-		:				\
-		: "a"(oldspptr), "d"(newsp)	\
-		: "%ebx", "%ecx", "%esi", "%edi", "memory", "cc");
-
 static inline
 void tf_uctx_transfer(struct tf_fiber *from, struct tf_fiber *to)
 {
@@ -130,5 +139,5 @@ void tf_uctx_transfer(struct tf_fiber *from, struct tf_fiber *to)
 
 	/* Switch stack pointers */
 	TF_BUG_ON(*ufrom->stack_guard != STACK_GUARD);
-	switch_fiber(&ufrom->current_sp, uto->current_sp);
+	switch_fiber(ufrom, uto);
 }