blob: f375991f7dd55d0f9126e92dc733b784441e8fa7 [file] [log] [blame]
@// Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
@// Use of this source code is governed by a BSD-style license
@// that can be found in the LICENSE file in the root of the source
@// tree. An additional intellectual property rights grant can be found
@// in the file PATENTS. All contributing project authors may
@// be found in the AUTHORS file in the root of the source tree.
@// This is a modification of
@// armSP_FFTInv_CCSToR_S32_preTwiddleRadix2_unsafe_s.s to support float
@// instead of SC32.
@// Description:
@// Compute the "preTwiddleRadix2" stage prior to the call to the complexFFT
@// It does a Z(k) = Feven(k) + jW^(-k) FOdd(k); k=0,1,2,...N/2-1 computation
@// Include standard headers
#include "dl/api/armCOMM_s.h"
#include "dl/api/omxtypes_s.h"
@// Import symbols required from other files
@// (For example tables)
@// Set debugging level
@// Guarding implementation by the processor name
@// Guarding implementation by the processor name
@//Input Registers
#define pSrc r0
#define pDst r1
#define pFFTSpec r2
#define scale r3
@// Output registers
#define result r0
@//Local Scratch Registers
#define argTwiddle r1
#define argDst r2
#define argScale r4
#define tmpOrder r4
#define pTwiddle r4
#define pOut r5
#define subFFTSize r7
#define subFFTNum r6
#define N r6
#define order r14
#define diff r9
@// Total num of radix stages required to complete the FFT
#define count r8
#define x0r r4
#define x0i r5
#define diffMinusOne r2
#define round r3
#define pOut1 r2
#define size r7
#define step r8
#define step1 r9
#define twStep r10
#define pTwiddleTmp r11
#define argTwiddle1 r12
#define zero r14
@// Neon registers
#define dX0 D0.F32
#define dShift D1.F32
#define dX1 D1.F32
#define dY0 D2.F32
#define dY1 D3.F32
#define dX0r D0.F32
#define dX0i D1.F32
#define dX1r D2.F32
#define dX1i D3.F32
#define dW0r D4.F32
#define dW0i D5.F32
#define dW1r D6.F32
#define dW1i D7.F32
#define dT0 D8.F32
#define dT1 D9.F32
#define dT2 D10.F32
#define dT3 D11.F32
#define qT0 D12.F32
#define qT1 D14.F32
#define qT2 D16.F32
#define qT3 D18.F32
#define dY0r D4.F32
#define dY0i D5.F32
#define dY1r D6.F32
#define dY1i D7.F32
#define dY2 D4.F32
#define dY3 D5.F32
#define dW0 D6.F32
#define dW1 D7.F32
#define dW0Tmp D10.F32
#define dW1Neg D11.F32
#define half D13.F32
@ Structure offsets for the FFTSpec
.set ARMsFFTSpec_N, 0
.set ARMsFFTSpec_pBitRev, 4
.set ARMsFFTSpec_pTwiddle, 8
.set ARMsFFTSpec_pBuf, 12
.MACRO FFTSTAGE scaled, inverse, name
@// Read the size from structure and take log
LDR N, [pFFTSpec, #ARMsFFTSpec_N]
@// Read other structure parameters
LDR pTwiddle, [pFFTSpec, #ARMsFFTSpec_pTwiddle]
LDR pOut, [pFFTSpec, #ARMsFFTSpec_pBuf]
VMOV half, 0.5
MOV size,N,ASR #1 @// preserve the contents of N
MOV step,N,LSL #2 @// step = N/2 * 8 bytes
@// Z(k) = 1/2 {[F(k) + F'(N/2-k)] +j*W^(-k) [F(k) - F'(N/2-k)]}
@// Note: W^(k) is stored as negated value and also need to
@// conjugate the values from the table
@// Z(0) : no need of twiddle multiply
@// Z(0) = 1/2 { [F(0) + F'(N/2)] +j [F(0) - F'(N/2)] }
VLD1 dX0,[pSrc],step
ADD pOut1,pOut,step @// pOut1 = pOut+ N/2*8 bytes
VLD1 dX1,[pSrc]!
@// twStep = 3N/8 * 8 bytes pointing to W^1
SUB twStep,step,size,LSL #1
MOV step1,size,LSL #2 @// step1 = N/4 * 8 = N/2*4 bytes
SUB step1,step1,#8 @// (N/4-1)*8 bytes
VADD dY0,dX0,dX1 @// [b+d | a+c]
VSUB dY1,dX0,dX1 @// [b-d | a-c]
VMUL dY0, dY0, half[0]
VMUL dY1, dY1, half[0]
@// dY0= [a-c | a+c] ;dY1= [b-d | b+d]
VZIP dY0,dY1
VSUB dX0,dY0,dY1
SUBS size,size,#2
VADD dX1,dY0,dY1
SUB pSrc,pSrc,step
VST1 dX0[0],[pOut1]!
ADD pTwiddleTmp,pTwiddle,#8 @// W^2
VST1 dX1[1],[pOut1]!
ADD argTwiddle1,pTwiddle,twStep @// W^1
BLT decrementScale\name
BEQ lastElement\name
@// Z(k) = 1/2[F(k) + F'(N/2-k)] +j*W^(-k) [F(k) - F'(N/2-k)]
@// Note: W^k is stored as negative values in the table and also
@// need to conjugate the values from the table.
@// Process 4 elements at a time. E.g: Z(1),Z(2) and Z(N/2-2),Z(N/2-1)
@// since both of them require F(1),F(2) and F(N/2-2),F(N/2-1)
SUB step,step,#24
evenOddButterflyLoop\name :
VLD1 dW0r,[argTwiddle1],step1
VLD1 dW1r,[argTwiddle1]!
VLD2 {dX0r,dX0i},[pSrc],step
SUB argTwiddle1,argTwiddle1,step1
VLD2 {dX1r,dX1i},[pSrc]!
SUB step1,step1,#8 @// (N/4-2)*8 bytes
VLD1 dW0i,[pTwiddleTmp],step1
VLD1 dW1i,[pTwiddleTmp]!
SUB pSrc,pSrc,step
SUB pTwiddleTmp,pTwiddleTmp,step1
VREV64 dX1r,dX1r
VREV64 dX1i,dX1i
SUBS size,size,#4
VSUB dT2,dX0r,dX1r @// a-c
VADD dT3,dX0i,dX1i @// b+d
VADD dT0,dX0r,dX1r @// a+c
VSUB dT1,dX0i,dX1i @// b-d
SUB step1,step1,#8
VMUL dT2, dT2, half[0]
VMUL dT3, dT3, half[0]
VMUL dT0, dT0, half[0]
VMUL dT1, dT1, half[0]
VZIP dW1r,dW1i
VZIP dW0r,dW0i
VMUL dX1r,dW1r,dT2
VMUL dX1i,dW1r,dT3
VMUL dX0r,dW0r,dT2
VMUL dX0i,dW0r,dT3
VMLS dX1r,dW1i,dT3
VMLA dX1i,dW1i,dT2
VMLA dX0r,dW0i,dT3
VMLS dX0i,dW0i,dT2
VADD dY1r,dT0,dX1i @// F(N/2 -1)
VSUB dY1i,dX1r,dT1
VREV64 dY1r,dY1r
VREV64 dY1i,dY1i
VADD dY0r,dT0,dX0i @// F(1)
VSUB dY0i,dT1,dX0r
VST2 {dY0r,dY0i},[pOut1],step
VST2 {dY1r,dY1i},[pOut1]!
SUB pOut1,pOut1,step
SUB step,step,#32 @// (N/2-4)*8 bytes
BGT evenOddButterflyLoop\name
@// set both the ptrs to the last element
SUB pSrc,pSrc,#8
SUB pOut1,pOut1,#8
@// Last element can be expanded as follows
@// 1/2[Z(k) + Z'(k)] - j w^-k [Z(k) - Z'(k)] (since W^k is stored as
@// -ve)
@// 1/2[(a+jb) + (a-jb)] - j w^-k [(a+jb) - (a-jb)]
@// 1/2[2a+j0] - j (c-jd) [0+j2b]
@// (a+bc, -bd)
@// Since (c,d) = (0,1) for the last element, result is just (a,-b)
lastElement\name :
VLD1 dX0r,[pSrc]
VST1 dX0r[0],[pOut1]!
VNEG dX0r,dX0r
VST1 dX0r[1],[pOut1]
decrementScale\name :
M_START armSP_FFTInv_CCSToR_F32_preTwiddleRadix2_unsafe,r4