Workaround for compiling LINT. Large kernels (like LINT) can have

branch targets that are too far apart for the BRADDR relocation.
This is caused by the branch prediction optimizationi in the atomic
inlines here, because they jump across sections.
The workaround is to suppress jumping to a different section when
compiling LINT. To generate correct code in that case, the section
directives are replaced by a branch and a label to deal with the
fall-through case. Reasonably good C compilers will optimize this
away anyway, so the end result isn't really that bad.

1 files changed, 32 insertions, 20 deletions

diff --git a/sys/alpha/include/atomic.h b/sys/alpha/include/atomic.h
index ba92cd6..1d1354a 100644
--- a/sys/alpha/include/atomic.h
+++ b/sys/alpha/include/atomic.h
@@ -32,6 +32,18 @@
 #include <machine/alpha_cpu.h>
 
 /*
+ * Quick and dirty workaround for compiling LINT. The kernel is too
+ * large to jump between sections without linker stubs/trampolines.
+ */
+#ifdef COMPILING_LINT
+#define	__COLD_SECTION	"br 3f\n"
+#define	__HOT_SECTION	"3:\n"
+#else
+#define	__COLD_SECTION	".section .text3,\"ax\"\n"
+#define	__HOT_SECTION	".previous\n"
+#endif
+
+/*
  * Various simple arithmetic on memory which is atomic in the presence
  * of interrupts and SMP safe.
  */
@@ -56,9 +68,9 @@ static __inline void atomic_set_32(volatile u_int32_t *p, u_int32_t v)
 		"bis %0, %3, %0\n\t"		/* calculate new value */
 		"stl_c %0, %1\n\t"		/* attempt to store */
 		"beq %0, 2f\n\t"		/* spin if failed */
-		".section .text3,\"ax\"\n"	/* improve branch prediction */
+		__COLD_SECTION			/* improve branch prediction */
 		"2:\tbr 1b\n"			/* try again */
-		".previous\n"
+		__HOT_SECTION
 		: "=&r" (temp), "=m" (*p)
 		: "m" (*p), "r" (v)
 		: "memory");
@@ -75,9 +87,9 @@ static __inline void atomic_clear_32(volatile u_int32_t *p, u_int32_t v)
 		"bic %0, %2, %0\n\t"		/* calculate new value */
 		"stl_c %0, %1\n\t"		/* attempt to store */
 		"beq %0, 2f\n\t"		/* spin if failed */
-		".section .text3,\"ax\"\n"	/* improve branch prediction */
+		__COLD_SECTION			/* improve branch prediction */
 		"2:\tbr 1b\n"			/* try again */
-		".previous\n"
+		__HOT_SECTION
 		: "=&r" (temp), "+m" (*p)
 		: "r" (v)
 		: "memory");
@@ -94,9 +106,9 @@ static __inline void atomic_add_32(volatile u_int32_t *p, u_int32_t v)
 		"addl %0, %2, %0\n\t"		/* calculate new value */
 		"stl_c %0, %1\n\t"		/* attempt to store */
 		"beq %0, 2f\n\t"		/* spin if failed */
-		".section .text3,\"ax\"\n"	/* improve branch prediction */
+		__COLD_SECTION			/* improve branch prediction */
 		"2:\tbr 1b\n"			/* try again */
-		".previous\n"
+		__HOT_SECTION
 		: "=&r" (temp), "+m" (*p)
 		: "r" (v)
 		: "memory");
@@ -113,9 +125,9 @@ static __inline void atomic_subtract_32(volatile u_int32_t *p, u_int32_t v)
 		"subl %0, %2, %0\n\t"		/* calculate new value */
 		"stl_c %0, %1\n\t"		/* attempt to store */
 		"beq %0, 2f\n\t"		/* spin if failed */
-		".section .text3,\"ax\"\n"	/* improve branch prediction */
+		__COLD_SECTION			/* improve branch prediction */
 		"2:\tbr 1b\n"			/* try again */
-		".previous\n"
+		__HOT_SECTION
 		: "=&r" (temp), "+m" (*p)
 		: "r" (v)
 		: "memory");
@@ -154,9 +166,9 @@ static __inline void atomic_set_64(volatile u_int64_t *p, u_int64_t v)
 		"bis %0, %2, %0\n\t"		/* calculate new value */
 		"stq_c %0, %1\n\t"		/* attempt to store */
 		"beq %0, 2f\n\t"		/* spin if failed */
-		".section .text3,\"ax\"\n"	/* improve branch prediction */
+		__COLD_SECTION			/* improve branch prediction */
 		"2:\tbr 1b\n"			/* try again */
-		".previous\n"
+		__HOT_SECTION
 		: "=&r" (temp), "+m" (*p)
 		: "r" (v)
 		: "memory");
@@ -173,9 +185,9 @@ static __inline void atomic_clear_64(volatile u_int64_t *p, u_int64_t v)
 		"bic %0, %2, %0\n\t"		/* calculate new value */
 		"stq_c %0, %1\n\t"		/* attempt to store */
 		"beq %0, 2f\n\t"		/* spin if failed */
-		".section .text3,\"ax\"\n"	/* improve branch prediction */
+		__COLD_SECTION			/* improve branch prediction */
 		"2:\tbr 1b\n"			/* try again */
-		".previous\n"
+		__HOT_SECTION
 		: "=&r" (temp), "+m" (*p)
 		: "r" (v)
 		: "memory");
@@ -192,9 +204,9 @@ static __inline void atomic_add_64(volatile u_int64_t *p, u_int64_t v)
 		"addq %0, %2, %0\n\t"		/* calculate new value */
 		"stq_c %0, %1\n\t"		/* attempt to store */
 		"beq %0, 2f\n\t"		/* spin if failed */
-		".section .text3,\"ax\"\n"	/* improve branch prediction */
+		__COLD_SECTION			/* improve branch prediction */
 		"2:\tbr 1b\n"			/* try again */
-		".previous\n"
+		__HOT_SECTION
 		: "=&r" (temp), "+m" (*p)
 		: "r" (v)
 		: "memory");
@@ -211,9 +223,9 @@ static __inline void atomic_subtract_64(volatile u_int64_t *p, u_int64_t v)
 		"subq %0, %2, %0\n\t"		/* calculate new value */
 		"stq_c %0, %1\n\t"		/* attempt to store */
 		"beq %0, 2f\n\t"		/* spin if failed */
-		".section .text3,\"ax\"\n"	/* improve branch prediction */
+		__COLD_SECTION			/* improve branch prediction */
 		"2:\tbr 1b\n"			/* try again */
-		".previous\n"
+		__HOT_SECTION
 		: "=&r" (temp), "+m" (*p)
 		: "r" (v)
 		: "memory");
@@ -375,9 +387,9 @@ atomic_cmpset_32(volatile u_int32_t* p, u_int32_t cmpval, u_int32_t newval)
 		"stl_c %0, %1\n\t"		/* attempt to store */
 		"beq %0, 3f\n\t"		/* if it failed, spin */
 		"2:\n"				/* done */
-		".section .text3,\"ax\"\n"	/* improve branch prediction */
+		__COLD_SECTION			/* improve branch prediction */
 		"3:\tbr 1b\n"			/* try again */
-		".previous\n"
+		__HOT_SECTION
 		: "=&r" (ret), "+m" (*p)
 		: "r" ((long)(int)cmpval), "r" (newval)
 		: "memory");
@@ -405,9 +417,9 @@ atomic_cmpset_64(volatile u_int64_t* p, u_int64_t cmpval, u_int64_t newval)
 		"stq_c %0, %1\n\t"		/* attempt to store */
 		"beq %0, 3f\n\t"		/* if it failed, spin */
 		"2:\n"				/* done */
-		".section .text3,\"ax\"\n"	/* improve branch prediction */
+		__COLD_SECTION			/* improve branch prediction */
 		"3:\tbr 1b\n"			/* try again */
-		".previous\n"
+		__HOT_SECTION
 		: "=&r" (ret), "+m" (*p)
 		: "r" (cmpval), "r" (newval)
 		: "memory");