Originally committed to x264 in 1637239a by Henrik Gramner who has
agreed to re-license it as LGPL. Original commit message follows.
x86: Avoid some bypass delays and false dependencies
A bypass delay of 1-3 clock cycles may occur on some CPUs when transitioning
between int and float domains, so try to avoid that if possible.
When allocating stack space with an alignment requirement that is larger
than the current stack alignment we need to store a copy of the original
stack pointer in order to be able to restore it later.
If we chose to use another register for this purpose we should not pick
eax/rax since it can be overwritten as a return value.
libavutil/x86/float_dsp_init.c(144) : warning C4028: formal parameter 1 different from declaration
libavutil/x86/float_dsp_init.c(144) : warning C4028: formal parameter 2 different from declaration
Allows emulation to work when dst is equal to src2 as long as the
instruction is commutative, e.g. `addps m0, m1, m0`.
Signed-off-by: Anton Khirnov <anton@khirnov.net>
The yasm/nasm preprocessor only checks the first token, which means that
parameters such as `dword [rax]` are treated as identifiers, which is
generally not what we want.
Signed-off-by: Anton Khirnov <anton@khirnov.net>
Those instructions are not commutative since they only change the first
element in the vector and leave the rest unmodified.
Signed-off-by: Anton Khirnov <anton@khirnov.net>
The yasm/nasm preprocessor only checks the first token, which means that
parameters such as `dword [rax]` are treated as identifiers, which is
generally not what we want.
Some debuggers/profilers use this metadata to determine which function a
given instruction is in; without it they get can confused by local labels
(if you haven't stripped those). On the other hand, some tools are still
confused even with this metadata. e.g. this fixes `gdb`, but not `perf`.
Currently only implemented for ELF.
Signed-off-by: Anton Khirnov <anton@khirnov.net>
The REP_RET workaround is only needed on old AMD cpus, and the labels clutter
up the symbol table and confuse debugging/profiling tools, so use EQU to
create SHN_ABS symbols instead of creating local labels. Furthermore, skip
the workaround completely in functions that definitely won't run on such cpus.
Note that EQU is just creating a local label when using nasm instead of yasm.
This is probably a bug, but at least it doesn't break anything.
Signed-off-by: Anton Khirnov <anton@khirnov.net>
When allocating stack space with a larger alignment than the known stack
alignment a temporary register is used for storing the stack pointer.
Ensure that this isn't one of the registers used for passing arguments.
Signed-off-by: Anton Khirnov <anton@khirnov.net>
* Correctly handle FMA instructions with memory operands.
* Print a warning if FMA instructions are used without the correct cpuflag.
* Simplify the instantiation code.
* Clarify documentation.
Only the last operand in FMA3 instructions can be a memory operand. When
converting FMA4 instructions to FMA3 instructions we can utilize the fact
that multiply is a commutative operation and reorder operands if necessary
to ensure that a memory operand is used only as the last operand.
Signed-off-by: Anton Khirnov <anton@khirnov.net>
Some debuggers/profilers use this metadata to determine which function a
given instruction is in; without it they get can confused by local labels
(if you haven't stripped those). On the other hand, some tools are still
confused even with this metadata. e.g. this fixes `gdb`, but not `perf`.
Currently only implemented for ELF.
The REP_RET workaround is only needed on old AMD cpus, and the labels clutter
up the symbol table and confuse debugging/profiling tools, so use EQU to
create SHN_ABS symbols instead of creating local labels. Furthermore, skip
the workaround completely in functions that definitely won't run on such cpus.
Note that EQU is just creating a local label when using nasm instead of yasm.
This is probably a bug, but at least it doesn't break anything.
When allocating stack space with a larger alignment than the known stack
alignment a temporary register is used for storing the stack pointer.
Ensure that this isn't one of the registers used for passing arguments.
* Correctly handle FMA instructions with memory operands.
* Print a warning if FMA instructions are used without the correct cpuflag.
* Simplify the instantiation code.
* Clarify documentation.
Only the last operand in FMA3 instructions can be a memory operand. When
converting FMA4 instructions to FMA3 instructions we can utilize the fact
that multiply is a commutative operation and reorder operands if necessary
to ensure that a memory operand is used only as the last operand.
James Almer
James Darnley
Henrik Gramner
Diego Biurrun
Michael Niedermayer
Alexandra Hájková
Anton Khirnov
Fiona Glaser
Ronald S. Bultje
Matthieu Bouron
Matt Oliver
Anton Mitrofanov
Vittorio Giovara
Timothy Gu
Geza Lore