add support for mips and mips64 r6 isa

mips32r6 and mips64r6 are actually new isas at both the asm source and
opcode levels (pre-r6 code cannot run on r6) and thus need to be
treated as a new subarch. the following changes are made, some of
which yield code generation improvements for non-r6 targets too:

- add subarch logic in configure script and reloc.h files for dynamic
  linker name.

- suppress use of .set mips2 asm directives (used to allow mips2
  atomic instructions on baseline mips1 builds; the kernel has to
  emulate them on mips1) except when actually needed. they cause wrong
  instruction encodings on r6, and pessimize inlining on at least some
  compilers.

- only hard-code sync instruction encoding on mips1.

- use "ZC" constraint instead of "m" constraint for llsc memory
  operands on r6, where the ll/sc instructions no longer accept full
  16-bit offsets.

- only hard-code rdhwr instruction encoding with .word on targets
  (pre-r2) where it may need trap-and-emulate by the kernel.
  otherwise, just use the instruction mnemonic, and allow an arbitrary
  destination register to be used.

1 files changed, 7 insertions, 1 deletions

diff --git a/arch/mips64/reloc.h b/arch/mips64/reloc.h
index 5933147c..bbd9bd9d 100644
--- a/arch/mips64/reloc.h
+++ b/arch/mips64/reloc.h
@@ -4,6 +4,12 @@
 #define _GNU_SOURCE
 #include <endian.h>
 
+#if __mips_isa_rev >= 6
+#define ISA_SUFFIX "r6"
+#else
+#define ISA_SUFFIX ""
+#endif
+
 #if __BYTE_ORDER == __LITTLE_ENDIAN
 #define ENDIAN_SUFFIX "el"
 #else
@@ -16,7 +22,7 @@
 #define FP_SUFFIX ""
 #endif
 
-#define LDSO_ARCH "mips64" ENDIAN_SUFFIX FP_SUFFIX
+#define LDSO_ARCH "mips64" ISA_SUFFIX ENDIAN_SUFFIX FP_SUFFIX
 
 #define TPOFF_K (-0x7000)