[PATCH] MIPS: Only use .set mips* assembler directives when an instruction is not supported in the current ISA

[Andrew Bennett <Andrew dot Bennett at imgtec dot com>]

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.



diff --git a/sysdeps/mips/bits/atomic.h b/sysdeps/mips/bits/atomic.h
index a391881..3754489 100644
--- a/sysdeps/mips/bits/atomic.h
+++ b/sysdeps/mips/bits/atomic.h
@@ -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
diff --git a/sysdeps/mips/nptl/tls.h b/sysdeps/mips/nptl/tls.h
index ef11457..e69c397 100644
--- a/sysdeps/mips/nptl/tls.h
+++ b/sysdeps/mips/nptl/tls.h
@@ -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
diff --git a/sysdeps/mips/sys/tas.h b/sysdeps/mips/sys/tas.h
index e14b5f0..2820ff6 100644
--- a/sysdeps/mips/sys/tas.h
+++ b/sysdeps/mips/sys/tas.h
@@ -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"
diff --git a/sysdeps/mips/tls-macros.h b/sysdeps/mips/tls-macros.h
index 3e87e42..a6fdfbc 100644
--- a/sysdeps/mips/tls-macros.h
+++ b/sysdeps/mips/tls-macros.h
@@ -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"		\
diff --git a/sysdeps/unix/mips/sysdep.h b/sysdeps/unix/mips/sysdep.h
index 4fd58f7..08595cc 100644
--- a/sysdeps/unix/mips/sysdep.h
+++ b/sysdeps/unix/mips/sysdep.h
@@ -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