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Patch to MIPS arch to allow overriding of HAL_*BIT_INDEX macros
- From: Daniel Helgason <dhelgason at shaw dot ca>
- To: ecos-patches at sourceware dot org
- Date: Wed, 10 Dec 2008 14:01:56 -0800
- Subject: Patch to MIPS arch to allow overriding of HAL_*BIT_INDEX macros
Some MIPS cores have an instruction to count leading zeros. This patch
allows MIPS variants and platforms to substitute their own methods to
compute bit indexes.
The attached file, mips_arch.patch, patches MIPS architecture files to
allow the HAL_LSBIT_INDEX and HAL_MSBIT_INDEX macros to be substituted
out. The current architecture macros will continue to be used if they
are not overridden.
The attached file, mips_mips32.patch, patches MIPS32 variant files to
override the HAL_LSBIT_INDEX and HAL_MSBIT_INDEX macros to use a more
efficient method to compute bit indexes.
Note: The MIPS64 variant, at least, should be patched in a similar
manner as the MIPS32 variant because it also has a 'CLZ' instruction.
--
+---------------------------------------------
| Daniel Helgason <dhelgason@shaw.ca>
Index: packages/hal/mips/arch/current/include/hal_arch.h
===================================================================
RCS file: /cvs/ecos/ecos/packages/hal/mips/arch/current/include/hal_arch.h,v
retrieving revision 1.18
diff -r1.18 hal_arch.h
128a129,130
> #ifndef CYGHWR_HAL_BIT_INDEXES_DEFINED
>
135a138,139
> #endif
>
Index: packages/hal/mips/arch/current/src/hal_misc.c
===================================================================
RCS file: /cvs/ecos/ecos/packages/hal/mips/arch/current/src/hal_misc.c,v
retrieving revision 1.30
diff -r1.30 hal_misc.c
301a302,304
>
> #ifndef CYGHWR_HAL_BIT_INDEXES_DEFINED
>
347a351,353
> #endif
>
>
Index: packages/hal/mips/mips32/current/include/var_arch.h
===================================================================
RCS file: /cvs/ecos/ecos/packages/hal/mips/mips32/current/include/var_arch.h,v
retrieving revision 1.5
diff -r1.5 var_arch.h
88a89,125
> // Bit manipulation macros
>
> #ifndef CYGHWR_HAL_BIT_INDEXES_DEFINED
>
> //--------------------------------------------------------
> // Determine the index of the ls bit of the supplied mask.
>
> #define HAL_LSBIT_INDEX(_index_, _mask_) \
> CYG_MACRO_START \
> unsigned _reg_; \
> \
> _reg_ = (_mask_); \
> _reg_ &= -_reg_; \
> asm volatile ("clz %0, %1\n" \
> : "=r" (_reg_) \
> : "r" (_reg_) ); \
> (_index_) = 31 - _reg_; \
> CYG_MACRO_END
>
> //--------------------------------------------------------
> // Determine the index of the ms bit of the supplied mask.
>
> #define HAL_MSBIT_INDEX(_index_, _mask_) \
> CYG_MACRO_START \
> unsigned _reg_; \
> \
> _reg_ = (_mask_); \
> asm volatile ("clz %0, %1\n" \
> : "=r" (_reg_) \
> : "r" (_reg_) ); \
> (_index_) = 31 - _reg_; \
> CYG_MACRO_END
>
> #define CYGHWR_HAL_BIT_INDEXES_DEFINED
> #endif
>
> //--------------------------------------------------------------------------