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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 01:13:33 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 01:13:33 +0000 |
commit | 086c044dc34dfc0f74fbe41f4ecb402b2cd34884 (patch) | |
tree | a4f824bd33cb075dd5aa3eb5a0a94af221bbe83a /media/kiss_fft/README.simd | |
parent | Adding debian version 124.0.1-1. (diff) | |
download | firefox-086c044dc34dfc0f74fbe41f4ecb402b2cd34884.tar.xz firefox-086c044dc34dfc0f74fbe41f4ecb402b2cd34884.zip |
Merging upstream version 125.0.1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'media/kiss_fft/README.simd')
-rw-r--r-- | media/kiss_fft/README.simd | 78 |
1 files changed, 0 insertions, 78 deletions
diff --git a/media/kiss_fft/README.simd b/media/kiss_fft/README.simd deleted file mode 100644 index b0fdac5506..0000000000 --- a/media/kiss_fft/README.simd +++ /dev/null @@ -1,78 +0,0 @@ -If you are reading this, it means you think you may be interested in using the SIMD extensions in kissfft -to do 4 *separate* FFTs at once. - -Beware! Beyond here there be dragons! - -This API is not easy to use, is not well documented, and breaks the KISS principle. - - -Still reading? Okay, you may get rewarded for your patience with a considerable speedup -(2-3x) on intel x86 machines with SSE if you are willing to jump through some hoops. - -The basic idea is to use the packed 4 float __m128 data type as a scalar element. -This means that the format is pretty convoluted. It performs 4 FFTs per fft call on signals A,B,C,D. - -For complex data, the data is interlaced as follows: -rA0,rB0,rC0,rD0, iA0,iB0,iC0,iD0, rA1,rB1,rC1,rD1, iA1,iB1,iC1,iD1 ... -where "rA0" is the real part of the zeroth sample for signal A - -Real-only data is laid out: -rA0,rB0,rC0,rD0, rA1,rB1,rC1,rD1, ... - -Compile with gcc flags something like --O3 -mpreferred-stack-boundary=4 -DUSE_SIMD=1 -msse - -Be aware of SIMD alignment. This is the most likely cause of segfaults. -The code within kissfft uses scratch variables on the stack. -With SIMD, these must have addresses on 16 byte boundaries. -Search on "SIMD alignment" for more info. - - - -Robin at Divide Concept was kind enough to share his code for formatting to/from the SIMD kissfft. -I have not run it -- use it at your own risk. It appears to do 4xN and Nx4 transpositions -(out of place). - -void SSETools::pack128(float* target, float* source, unsigned long size128) -{ - __m128* pDest = (__m128*)target; - __m128* pDestEnd = pDest+size128; - float* source0=source; - float* source1=source0+size128; - float* source2=source1+size128; - float* source3=source2+size128; - - while(pDest<pDestEnd) - { - *pDest=_mm_set_ps(*source3,*source2,*source1,*source0); - source0++; - source1++; - source2++; - source3++; - pDest++; - } -} - -void SSETools::unpack128(float* target, float* source, unsigned long size128) -{ - - float* pSrc = source; - float* pSrcEnd = pSrc+size128*4; - float* target0=target; - float* target1=target0+size128; - float* target2=target1+size128; - float* target3=target2+size128; - - while(pSrc<pSrcEnd) - { - *target0=pSrc[0]; - *target1=pSrc[1]; - *target2=pSrc[2]; - *target3=pSrc[3]; - target0++; - target1++; - target2++; - target3++; - pSrc+=4; - } -} |