Tool/software: Code Composer Studio
Looking to optimize c++ code that is a simple dot product of timeData
void Math::DotProduct(float* restrict timeData, float* restrict operand1, float* restrict operand2)
{
int i = 0;
float real = 0;
float imag = 0;
_nassert((int) timeData % 8 == 0);
_nassert((int) operand1 % 8 == 0);
_nassert((int) operand2 % 8 == 0);
#pragma MUST_ITERATE(8,,2)
for (i=0; i<m_nLen; i++) {
real += timeData[i] * operand1[i];
imag += timeData[i] * operand2[i];
}
m_real = real;
m_imag = imag;
}
Doing a multiply and add; the compiler optimized loop info:
;*----------------------------------------------------------------------------*
;* SOFTWARE PIPELINE INFORMATION
;*
;* Loop found in file : C:/Code/SineMsmt.cpp
;* Loop source line : 312
;* Loop opening brace source line : 312
;* Loop closing brace source line : 315
;* Loop Unroll Multiple : 2x
;* Known Minimum Trip Count : 2
;* Known Max Trip Count Factor : 1
;* Loop Carried Dependency Bound(^) : 4
;* Unpartitioned Resource Bound : 2
;* Partitioned Resource Bound(*) : 3
;* Resource Partition:
;* A-side B-side
;* .L units 0 0
;* .S units 0 0
;* .D units 2 1
;* .M units 2 2
;* .X cross paths 1 3*
;* .T address paths 3* 3*
;* Long read paths 0 0
;* Long write paths 0 0
;* Logical ops (.LS) 2 2 (.L or .S unit)
;* Addition ops (.LSD) 0 1 (.L or .S or .D unit)
;* Bound(.L .S .LS) 1 1
;* Bound(.L .S .D .LS .LSD) 2 2
;*
;* Searching for software pipeline schedule at ...
;* ii = 4 Schedule found with 4 iterations in parallel
;*
;* Register Usage Table:
;* +-----------------------------------------------------------------+
;* |AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA|BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB|
;* |00000000001111111111222222222233|00000000001111111111222222222233|
;* |01234567890123456789012345678901|01234567890123456789012345678901|
;* |--------------------------------+--------------------------------|
;* 0: | *** * * * | * |
;* 1: | * * | *** |
;* 2: | *** * | *** ** |
;* 3: | ****** ** | **** |
;* +-----------------------------------------------------------------+
;*
;* Done
;*
;* Loop will be splooped
;* Collapsed epilog stages : 0
;* Collapsed prolog stages : 0
;* Minimum required memory pad : 0 bytes
;*
;* For further improvement on this loop, try option -mh8
;*
;* Minimum safe trip count : 1 (after unrolling)
;* Min. prof. trip count (est.) : 3 (after unrolling)
;*
;* Mem bank conflicts/iter(est.) : { min 0.000, est 0.000, max 0.000 }
;* Mem bank perf. penalty (est.) : 0.0%
;*
;*
;* Total cycles (est.) : 12 + trip_cnt * 4
;*----------------------------------------------------------------------------*
;* SINGLE SCHEDULED ITERATION
;*
;* $C$C867:
;* 0 LDNDW .D2T2 *B6++(8),B5:B4 ; |313|
;* 1 LDNDW .D1T1 *A16++(8),A5:A4 ; |313|
;* 2 LDNDW .D1T1 *A3++(8),A7:A6 ; |314|
;* 3 NOP 3
;* 6 MPYSP .M2X A5,B5,B9 ; |313|
;* 7 MPYSP .M1 A4,A6,A17 ; |314|
;* || MPYSP .M2X A4,B4,B5 ; |313|
;* 8 MPYSP .M1 A5,A7,A4 ; |314|
;* 9 NOP 1
;* 10 ADDSP .L2 B9,B8,B8 ; |313| ^
;* 11 ADDSP .L2 B5,B7,B7 ; |313| ^
;* || ADDSP .L1 A17,A8,A8 ; |314| ^
;* 12 ADDSP .L1 A4,A9,A9 ; |314| ^
;* || SPBR $C$C867
;* 13 NOP 3
;* 16 ; BRANCHCC OCCURS {$C$C867} ; |312|
The ii is limited by the add functions, which depend on the previous loop.
Since this is a simple add function though, two (or more) totals can be done in parallel and summed later; loop ii+1 doesnt really depend on loop ii.
Is there any way to tell the compiler this, or get the compiler to use this to lower the Loop Carry Dependence Bound?
