@//
@//  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_CToC_SC32_Sfs_s.s
@// OpenMAX DL: v1.0.2
@// Last Modified Revision:   6675
@// Last Modified Date:       Fri, 06 Jul 2007
@// 
@// (c) Copyright 2007-2008 ARM Limited. All Rights Reserved.
@// 
@// 
@//
@// Description:
@// Compute an inverse FFT for a complex signal
@// 

        
@// Include standard headers

#include "dl/api/armCOMM_s.h"
#include "dl/api/omxtypes_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   
        
@// 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

@// Neon registers

#define dX0	D0.S32
#define dShift	D1.S32



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

    @// Write function header
        M_START     omxSP_FFTInv_CToC_SC32_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]
                
        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
