MIPS: Only use .set mips* assembler directives when an instruction is not supported in the current ISA
Commit Message
Hi,
There are a few .set mips* assembler directives used in the MIPS specific sysdep
code that force an instruction to be assembled for a specific ISA. The reason for
these is to allow an instruction to be encoded when it might not be supported
in the current ISA. When the code is run the Linux kernel will trap and emulate
any unsupported instructions. Unfortunately, forcing a specific ISA means that
when assembling for a newer ISA, where the instruction has a different encoding,
the wrong encoding will be used.
The patch and ChangeLog below only makes use of the .set mips* assembler directive
when using an ISA below where the instruction was introduced.
I have built and tested the patch for: mips1, mips2 and mips32r2, and there are no
new regressions.
Ok to commit?
Many thanks,
Andrew
* sysdeps/mips/bits/atomic.h: Only use .set mips2 if the current ISA is below
mips2.
* sysdeps/mips/sys/tas.h: Likewise.
* sysdeps/mips/nptl/tls.h: Only use .set mips32r2 if the current ISA is below
mips32r2.
* sysdeps/mips/tls-macros.h (TLS_RDHWR): New define.
(TLS_IE): Updated to use the TLD_RDHWR macro.
(TLS_LE): Likewise.
Comments
On Fri, 4 Sep 2015, Andrew Bennett wrote:
> Ok to commit?
OK, though your ChangeLog entry should describe things in terms of the
named entities and preprocessor conditionals changed, e.g.:
* sysdeps/mips/sys/tas.h (_test_and_set) [__mips >= 2]: Do not use
.set mips2.
@@ -38,7 +38,7 @@ typedef uintptr_t uatomicptr_t;
typedef intmax_t atomic_max_t;
typedef uintmax_t uatomic_max_t;
-#if _MIPS_SIM == _ABIO32
+#if _MIPS_SIM == _ABIO32 && __mips < 2
#define MIPS_PUSH_MIPS2 ".set mips2\n\t"
#else
#define MIPS_PUSH_MIPS2
@@ -25,6 +25,8 @@
# include <stdbool.h>
# include <stddef.h>
# include <stdint.h>
+/* Get system call information. */
+# include <sysdep.h>
/* Type for the dtv. */
typedef union dtv
@@ -42,29 +44,37 @@ typedef union dtv
# define READ_THREAD_POINTER() (__builtin_thread_pointer ())
#else
/* Note: rd must be $v1 to be ABI-conformant. */
-# define READ_THREAD_POINTER() \
- ({ void *__result; \
- asm volatile (".set\tpush\n\t.set\tmips32r2\n\t" \
- "rdhwr\t%0, $29\n\t.set\tpop" : "=v" (__result)); \
- __result; })
+# if __mips_isa_rev >= 2
+# define READ_THREAD_POINTER() \
+ ({ void *__result; \
+ asm volatile ("rdhwr\t%0, $29" : "=v" (__result)); \
+ __result; })
+# else
+# define READ_THREAD_POINTER() \
+ ({ void *__result; \
+ asm volatile (".set\tpush\n\t.set\tmips32r2\n\t" \
+ "rdhwr\t%0, $29\n\t.set\tpop" : "=v" (__result)); \
+ __result; })
+# endif
#endif
#else /* __ASSEMBLER__ */
# include <tcb-offsets.h>
-# define READ_THREAD_POINTER(rd) \
- .set push; \
- .set mips32r2; \
- rdhwr rd, $29; \
- .set pop
+# if __mips_isa_rev >= 2
+# define READ_THREAD_POINTER(rd) rdhwr rd, $29
+# else
+# define READ_THREAD_POINTER(rd) \
+ .set push; \
+ .set mips32r2; \
+ rdhwr rd, $29; \
+ .set pop
+# endif
#endif /* __ASSEMBLER__ */
#ifndef __ASSEMBLER__
-/* Get system call information. */
-# include <sysdep.h>
-
/* The TP points to the start of the thread blocks. */
# define TLS_DTV_AT_TP 1
# define TLS_TCB_AT_TP 0
@@ -41,7 +41,7 @@ __NTH (_test_and_set (int *__p, int __v))
__asm__ __volatile__
("/* Inline test and set */\n"
".set push\n\t"
-#if _MIPS_SIM == _ABIO32
+#if _MIPS_SIM == _ABIO32 && __mips < 2
".set mips2\n\t"
#endif
"sync\n\t"
@@ -2,6 +2,7 @@
#include <sys/cdefs.h>
#include <sys/asm.h>
+#include <sysdep.h>
#define __STRING2(X) __STRING(X)
#define ADDU __STRING2(PTR_ADDU)
@@ -38,6 +39,14 @@
# define UNLOAD_GP
#endif
+# if __mips_isa_rev >= 2
+# define TLS_RDHWR "rdhwr\t%0,$29"
+# else
+# define TLS_RDHWR \
+ ".set push\n\t.set mips32r2\n\t" \
+ "rdhwr\t%0,$29\n\t.set pop"
+#endif
+
#ifndef __mips16
# define TLS_GD(x) \
({ void *__result, *__tmp; \
@@ -60,8 +69,7 @@
__result; })
# define TLS_IE(x) \
({ void *__result, *__tmp; \
- asm (".set push\n\t.set mips32r2\n\t" \
- "rdhwr\t%0,$29\n\t.set pop" \
+ asm (TLS_RDHWR \
: "=v" (__result)); \
asm (LOAD_GP LW " $3,%%gottprel(" #x ")($28)\n\t" \
ADDU " %0,%0,$3" \
@@ -71,8 +79,7 @@
__result; })
# define TLS_LE(x) \
({ void *__result; \
- asm (".set push\n\t.set mips32r2\n\t" \
- "rdhwr\t%0,$29\n\t.set pop" \
+ asm (TLS_RDHWR \
: "=v" (__result)); \
asm ("lui $3,%%tprel_hi(" #x ")\n\t" \
"addiu $3,$3,%%tprel_lo(" #x ")\n\t" \
@@ -19,6 +19,10 @@
#include <sgidefs.h>
#include <sysdeps/unix/sysdep.h>
+#ifndef __mips_isa_rev
+# define __mips_isa_rev 0
+#endif
+
#ifdef __ASSEMBLER__
#include <regdef.h>
@@ -78,8 +82,4 @@
# define L(label) .L ## label
#endif
-#ifndef __mips_isa_rev
-# define __mips_isa_rev 0
-#endif
-
#endif