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libavutils: Add parse_r helper for MIPS

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That helper grab from kernel code can allow us to inline
newer instructions (not implemented by the assembler) in
a elegant manner.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Shiyou Yin <yinshiyou-hf@loongson.cn>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Jiaxun Yang 2020-07-18 23:35:38 +08:00 committed by Michael Niedermayer
parent d57d6def73
commit d5380f068d
1 changed files with 42 additions and 0 deletions
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42
libavutil/mips/asmdefs.h
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@ -55,4 +55,46 @@
# define PTR_SLL "sll " # define PTR_SLL "sll "
#endif #endif
/*
* parse_r var, r - Helper assembler macro for parsing register names.
*
* This converts the register name in $n form provided in \r to the
* corresponding register number, which is assigned to the variable \var. It is
* needed to allow explicit encoding of instructions in inline assembly where
* registers are chosen by the compiler in $n form, allowing us to avoid using
* fixed register numbers.
*
* It also allows newer instructions (not implemented by the assembler) to be
* transparently implemented using assembler macros, instead of needing separate
* cases depending on toolchain support.
*
* Simple usage example:
* __asm__ __volatile__("parse_r __rt, %0\n\t"
* ".insn\n\t"
* "# di %0\n\t"
* ".word (0x41606000 | (__rt << 16))"
* : "=r" (status);
*/
/* Match an individual register number and assign to \var */
#define _IFC_REG(n) \
".ifc \\r, $" #n "\n\t" \
"\\var = " #n "\n\t" \
".endif\n\t"
__asm__(".macro parse_r var r\n\t"
"\\var = -1\n\t"
_IFC_REG(0) _IFC_REG(1) _IFC_REG(2) _IFC_REG(3)
_IFC_REG(4) _IFC_REG(5) _IFC_REG(6) _IFC_REG(7)
_IFC_REG(8) _IFC_REG(9) _IFC_REG(10) _IFC_REG(11)
_IFC_REG(12) _IFC_REG(13) _IFC_REG(14) _IFC_REG(15)
_IFC_REG(16) _IFC_REG(17) _IFC_REG(18) _IFC_REG(19)
_IFC_REG(20) _IFC_REG(21) _IFC_REG(22) _IFC_REG(23)
_IFC_REG(24) _IFC_REG(25) _IFC_REG(26) _IFC_REG(27)
_IFC_REG(28) _IFC_REG(29) _IFC_REG(30) _IFC_REG(31)
".iflt \\var\n\t"
".error \"Unable to parse register name \\r\"\n\t"
".endif\n\t"
".endm");
#endif /* AVCODEC_MIPS_ASMDEFS_H */ #endif /* AVCODEC_MIPS_ASMDEFS_H */