@//
@//  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 file was originally licensed as follows. It has been
@//  relicensed with permission from the copyright holders.
@//

@// 
@// File Name:  omxSP_FFTInv_CCSToR_S32_Sfs_s.s
@// OpenMAX DL: v1.0.2
@// Last Modified Revision:   7469
@// Last Modified Date:       Thu, 20 Sep 2007
@// 
@// (c) Copyright 2007-2008 ARM Limited. All Rights Reserved.
@// 
@// 
@//
@// Description:
@// Compute an inverse FFT for a complex signal
@// 


@// Include standard headers

#include "omxtypes_s.h"
#include "armCOMM_s.h"
        
        
@// Import symbols required from other files
@// (For example tables)
        
        .extern  armSP_FFTInv_CToC_SC32_Sfs_Radix2_fs_OutOfPlace_unsafe 
        .extern  armSP_FFTInv_CToC_SC32_Radix2_fs_OutOfPlace_unsafe
        .extern  armSP_FFTInv_CToC_SC32_Radix4_fs_OutOfPlace_unsafe 
        .extern  armSP_FFTInv_CToC_SC32_Radix8_fs_OutOfPlace_unsafe 
        .extern  armSP_FFTInv_CToC_SC32_Radix4_OutOfPlace_unsafe
        .extern  armSP_FFTInv_CToC_SC32_Sfs_Radix4_fs_OutOfPlace_unsafe 
        .extern  armSP_FFTInv_CToC_SC32_Sfs_Radix8_fs_OutOfPlace_unsafe 
        .extern  armSP_FFTInv_CToC_SC32_Sfs_Radix4_OutOfPlace_unsafe
        .extern  armSP_FFTInv_CToC_SC32_Sfs_Radix2_OutOfPlace_unsafe
        .extern  armSP_FFTInv_CToC_SC32_Radix2_OutOfPlace_unsafe
        .extern  armSP_FFTInv_CCSToR_S32_Sfs_preTwiddleRadix2_unsafe        
        .extern  armSP_FFTInv_CCSToR_S32_preTwiddleRadix2_unsafe        
        
        
@// Set debugging level        
@//DEBUG_ON    SETL {TRUE}


@// Guarding implementation by the processor name
    
    
      @// Guarding implementation by the processor name
    
@// Import symbols required from other files
@// (For example tables)
        .extern  armSP_FFTInv_CToC_SC32_Radix4_ls_OutOfPlace_unsafe     
        .extern  armSP_FFTInv_CToC_SC32_Radix2_ls_OutOfPlace_unsafe
        .extern  armSP_FFTInv_CToC_SC32_Sfs_Radix2_ls_OutOfPlace_unsafe
        .extern  armSP_FFTInv_CToC_SC32_Sfs_Radix4_ls_OutOfPlace_unsafe
        
    
@//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 comple 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.S32
#define dShift  D1.S32
#define dX1     D1.S32
#define dY0     D2.S32
#define dY1     D3.S32
#define dX0r    D0.S32            
#define dX0i    D1.S32
#define dX1r    D2.S32
#define dX1i    D3.S32
#define dW0r    D4.S32
#define dW0i    D5.S32
#define dW1r    D6.S32
#define dW1i    D7.S32
#define dT0     D8.S32
#define dT1     D9.S32
#define dT2     D10.S32
#define dT3     D11.S32
#define qT0     Q6.S64
#define qT1     Q7.S64
#define qT2     Q8.S64
#define qT3     Q9.S64
#define dY0r    D4.S32
#define dY0i    D5.S32
#define dY1r    D6.S32
#define dY1i    D7.S32
#define dzero   D20.S32

#define dY2     D4.S32
#define dY3     D5.S32
#define dW0     D6.S32
#define dW1     D7.S32
#define dW0Tmp  D10.S32
#define dW1Neg  D11.S32


    @// Allocate stack memory required by the function
        M_ALLOC4        diffOnStack, 4

    @// Write function header
        M_START     omxSP_FFTInv_CCSToR_S32_Sfs,r11,d15
        
@ Structure offsets for the FFTSpec             
        .set    ARMsFFTSpec_N, 0
        .set    ARMsFFTSpec_pBitRev, 4
        .set    ARMsFFTSpec_pTwiddle, 8
        .set    ARMsFFTSpec_pBuf, 12

        @// Define stack arguments
        
        @// 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]
        
        @//  N=1 Treat seperately  
        CMP     N,#1
        BGT     sizeGreaterThanOne
        VLD1    dX0[0],[pSrc]
        RSB     scale,scale,#0                        @// to use VRSHL for right shift by a variable
        VMOV    dShift[0],scale
        VRSHL   dX0,dShift
        VST1    dX0[0],[pDst]
                
        B       End
        
sizeGreaterThanOne:     
        
        @// Call the preTwiddle Radix2 stage before doing the compledIFFT
        
        @// The following conditional BL combination would work since 
        @// evenOddButterflyLoop in the first call would set Z flag to zero
        
        CMP     scale,#0
        BLEQ    armSP_FFTInv_CCSToR_S32_preTwiddleRadix2_unsafe
        BLGT    armSP_FFTInv_CCSToR_S32_Sfs_preTwiddleRadix2_unsafe
                
        
complexIFFT:    
        
        ASR     N,N,#1                             @// N/2 point complex IFFT 
        ADD     pSrc,pOut,N,LSL #3                 @// set pSrc as pOut1 
                        
        CLZ     order,N                             @// N = 2^order 
        RSB     order,order,#31     
        MOV     subFFTSize,#1
        @//MOV     subFFTNum,N
        
        ADD     scale,scale,order                   @// FFTInverse has a final scaling factor by N
        
        CMP     order,#3
        BGT     orderGreaterthan3                   @// order > 3
                
        CMP     order,#1
        BGE     orderGreaterthan0                   @// order > 0
        M_STR   scale, diffOnStack,LT               @// order = 0
        VLD1    dX0,[pSrc]
        VST1    dX0,[pDst]
        MOV     pSrc,pDst
        BLT     FFTEnd
        
orderGreaterthan0:      
        @// set the buffers appropriately for various orders
        CMP     order,#2
        MOVNE   argDst,pDst        
        MOVEQ   argDst,pOut
        MOVEQ   pOut,pDst                           @// Pass the first stage destination in RN5
        MOV     argTwiddle,pTwiddle
        @// Store the scale factor and scale at the end
        SUB     diff,scale,order
        M_STR   diff, diffOnStack
        BGE     orderGreaterthan1
        BLLT    armSP_FFTInv_CToC_SC32_Sfs_Radix2_fs_OutOfPlace_unsafe  @// order = 1
        B       FFTEnd

orderGreaterthan1:      
        MOV     tmpOrder,order                          @// tmpOrder = RN 4
        BL      armSP_FFTInv_CToC_SC32_Sfs_Radix2_fs_OutOfPlace_unsafe        
        CMP     tmpOrder,#2
        BLGT    armSP_FFTInv_CToC_SC32_Sfs_Radix2_OutOfPlace_unsafe
        BL      armSP_FFTInv_CToC_SC32_Sfs_Radix2_ls_OutOfPlace_unsafe
        B       FFTEnd
        

orderGreaterthan3:             
        @// check scale = 0 or scale = order
        SUBS    diff, scale, order                 @// scale > order 
        MOVGT   scale,order     
        BGE     specialScaleCase                   @// scale = 0 or scale = order 
        CMP     scale,#0
        BEQ     specialScaleCase
        B       generalScaleCase
        
specialScaleCase:                                           @//  scale = 0 or scale = order  and order >= 2     
        
        TST     order, #2                           @// Set input args to fft stages
        MOVNE   argDst,pDst        
        MOVEQ   argDst,pOut
        MOVEQ   pOut,pDst                           @// Pass the first stage destination in RN5
        MOV     argTwiddle,pTwiddle  

        CMP      diff,#0
        M_STR    diff, diffOnStack
        BGE      scaleEqualsOrder  
       
        @//check for even or odd order
        @// NOTE: The following combination of BL's would work fine eventhough the first
        @// BL would corrupt the flags. This is because the end of the "grpZeroSetLoop" loop inside 
        @// armSP_FFTInv_CToC_SC32_Radix4_fs_OutOfPlace_unsafe sets the Z flag to EQ
        
        TST     order,#0x00000001
        BLEQ    armSP_FFTInv_CToC_SC32_Radix4_fs_OutOfPlace_unsafe 
        BLNE    armSP_FFTInv_CToC_SC32_Radix8_fs_OutOfPlace_unsafe
        
        CMP        subFFTNum,#4
        BLT     FFTEnd
         

unscaledRadix4Loop:     
        BEQ        lastStageUnscaledRadix4
         BL        armSP_FFTInv_CToC_SC32_Radix4_OutOfPlace_unsafe
         CMP        subFFTNum,#4
         B        unscaledRadix4Loop
         
lastStageUnscaledRadix4:        
        BL      armSP_FFTInv_CToC_SC32_Radix4_ls_OutOfPlace_unsafe 
        B        FFTEnd        
         

scaleEqualsOrder:                
        @//check for even or odd order
        @// NOTE: The following combination of BL's would work fine eventhough the first
        @// BL would corrupt the flags. This is because the end of the "grpZeroSetLoop" loop inside 
        @// armSP_FFTInv_CToC_SC32_Radix4_fs_OutOfPlace_unsafe sets the Z flag to EQ
                
        TST     order,#0x00000001
        BLEQ    armSP_FFTInv_CToC_SC32_Sfs_Radix4_fs_OutOfPlace_unsafe 
        BLNE    armSP_FFTInv_CToC_SC32_Sfs_Radix8_fs_OutOfPlace_unsafe 
        
        CMP        subFFTNum,#4
        BLT     FFTEnd
        

scaledRadix4Loop:       
        BEQ        lastStageScaledRadix4
         BL        armSP_FFTInv_CToC_SC32_Sfs_Radix4_OutOfPlace_unsafe
         CMP        subFFTNum,#4
         B        scaledRadix4Loop         
         
lastStageScaledRadix4:  
        BL      armSP_FFTInv_CToC_SC32_Sfs_Radix4_ls_OutOfPlace_unsafe 
        B        FFTEnd        
        
generalScaleCase:                                               @// 0 < scale < order and order >= 2
        @// Determine the correct destination buffer
        SUB     diff,order,scale
        TST     diff,#0x01
        ADDEQ   count,scale,diff,LSR #1         @// count = scale + (order - scale)/2
        MOVNE   count,order
        TST     count,#0x01                     @// Is count even or odd ?
        
        MOVNE   argDst,pDst                     @// Set input args to fft stages
        MOVEQ   argDst,pOut
        MOVEQ   pOut,pDst                       @// Pass the first stage destination in RN5
        MOV     argTwiddle,pTwiddle  

        M_STR   diff, diffOnStack    
        
        MOV     argScale,scale                  @// Put scale in RN4 so as to save and restore
        BL      armSP_FFTInv_CToC_SC32_Sfs_Radix2_fs_OutOfPlace_unsafe     @// scaled first stage
        SUBS    argScale,argScale,#1
        
scaledRadix2Loop:               
        BLGT    armSP_FFTInv_CToC_SC32_Sfs_Radix2_OutOfPlace_unsafe
        SUBS    argScale,argScale,#1            @// save and restore scale (RN4) in the scaled stages
        BGT     scaledRadix2Loop
        
        
        M_LDR   diff, diffOnStack  
        @//check for even or odd order
        TST     diff,#0x00000001
        BEQ     generalUnscaledRadix4Loop
        B       unscaledRadix2Loop

generalUnscaledRadix4Loop:      
        CMP        subFFTNum,#4
         BEQ        generalLastStageUnscaledRadix4
         BL        armSP_FFTInv_CToC_SC32_Radix4_OutOfPlace_unsafe
         B        generalUnscaledRadix4Loop 
         
generalLastStageUnscaledRadix4: 
        BL      armSP_FFTInv_CToC_SC32_Radix4_ls_OutOfPlace_unsafe 
        B        End             
             

unscaledRadix2Loop:     
        CMP        subFFTNum,#2
         BEQ        generalLastStageUnscaledRadix2
         BL        armSP_FFTInv_CToC_SC32_Radix2_OutOfPlace_unsafe
         B        unscaledRadix2Loop        

generalLastStageUnscaledRadix2: 
        BL      armSP_FFTInv_CToC_SC32_Radix2_ls_OutOfPlace_unsafe 
        B        End             

       
FFTEnd:                                               @// Does only the scaling
        
        M_LDR   diff, diffOnStack  
        CMP     diff,#0
        BLE     End
        
        RSB     diff,diff,#0                        @// to use VRSHL for right shift by a variable
        VDUP    dShift,diff     
        
scaleFFTData:                                           @// N = subFFTSize  ; dataptr = pDst  ; scale = diff
        VLD1    {dX0},[pSrc]            @// pSrc contains pDst pointer
        SUBS    subFFTSize,subFFTSize,#1
        VRSHL   dX0,dShift
        VST1    {dX0},[pSrc]!
                
        BGT     scaleFFTData
        
                       
End:                            
        @// Set return value
        MOV     result, #OMX_Sts_NoErr       

        @// Write function tail
        M_END
        
    
        .end