diff options
| author | Paul Burton <paul.burton@imgtec.com> | 2014-09-11 08:30:20 +0100 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2014-11-24 07:45:07 +0100 |
| commit | 4227a2d4efc9c84f35826dc4d1e6dc183f6c1c05 (patch) | |
| tree | bea7e276a3dc164bc215f0a5feb4604305ff0547 /arch/mips/include/asm/thread_info.h | |
| parent | d175ed2bd6544474dcc99d74f8155c2ba44e8db2 (diff) | |
| download | linux-4227a2d4efc9c84f35826dc4d1e6dc183f6c1c05.tar.gz | |
MIPS: Support for hybrid FPRs
Hybrid FPRs is a scheme where scalar FP registers are 64b wide, but
accesses to odd indexed single registers use bits 63:32 of the
preceeding even indexed 64b register. In this mode all FP code
except that built for the plain FP64 ABI can execute correctly. Most
notably a combination of FP64A & FP32 code can execute correctly,
allowing for existing FP32 binaries to be linked with new FP64A binaries
that can make use of 64 bit FP & MSA.
Hybrid FPRs are implemented by setting both the FR & FRE bits, trapping
& emulating single precision FP instructions (via Reserved Instruction
exceptions) whilst allowing others to execute natively. It therefore has
a penalty in terms of execution speed, and should only be used when no
fully native mode can be. As more binaries are recompiled to use either
the FPXX or FP64(A) ABIs, the need for hybrid FPRs should diminish.
However in the short to mid term it allows for a gradual transition
towards that world, rather than a complete ABI break which is not
feasible for some users & not desirable for many.
A task will be executed using the hybrid FPR scheme when its
TIF_HYBRID_FPREGS flag is set & TIF_32BIT_FPREGS is clear. A further
patch will set the flags as necessary, this patch simply adds the
infrastructure necessary for the hybrid FPR mode to work.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/7683/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/include/asm/thread_info.h')
| -rw-r--r-- | arch/mips/include/asm/thread_info.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/mips/include/asm/thread_info.h b/arch/mips/include/asm/thread_info.h index 7de865805deb..99eea59604e9 100644 --- a/arch/mips/include/asm/thread_info.h +++ b/arch/mips/include/asm/thread_info.h @@ -116,6 +116,7 @@ static inline struct thread_info *current_thread_info(void) #define TIF_LOAD_WATCH 25 /* If set, load watch registers */ #define TIF_SYSCALL_TRACEPOINT 26 /* syscall tracepoint instrumentation */ #define TIF_32BIT_FPREGS 27 /* 32-bit floating point registers */ +#define TIF_HYBRID_FPREGS 28 /* 64b FP registers, odd singles in bits 63:32 of even doubles */ #define TIF_USEDMSA 29 /* MSA has been used this quantum */ #define TIF_MSA_CTX_LIVE 30 /* MSA context must be preserved */ #define TIF_SYSCALL_TRACE 31 /* syscall trace active */ @@ -135,6 +136,7 @@ static inline struct thread_info *current_thread_info(void) #define _TIF_FPUBOUND (1<<TIF_FPUBOUND) #define _TIF_LOAD_WATCH (1<<TIF_LOAD_WATCH) #define _TIF_32BIT_FPREGS (1<<TIF_32BIT_FPREGS) +#define _TIF_HYBRID_FPREGS (1<<TIF_HYBRID_FPREGS) #define _TIF_USEDMSA (1<<TIF_USEDMSA) #define _TIF_MSA_CTX_LIVE (1<<TIF_MSA_CTX_LIVE) #define _TIF_SYSCALL_TRACEPOINT (1<<TIF_SYSCALL_TRACEPOINT) |