Re: induct regression in gcc 4.3.1

[Tim Prince <TimothyPrince at sbcglobal dot net>]

Jack Howarth wrote:
>      While generating .s files for induct.f90, I discovered that
> when I compile...
>
> gfortran -fassociative-math -fno-signed-zeros -O3 induct.f90
>
> or
>
> gfortran -fassociative-math -fno-trapping-math -O3 induct.f90
>
> I get the warning...
>
> f951: warning: -fassociative-math disabled; other options take precedence
>
> Only...
>
> gfortran -fassociative-math -fno-signed-zeros -fno-trapping-math -O3 induct.f90
>
> inhibits this message. This strongly suggests that the -fassociative-math 
> (which is only active in concert with -fno-signed-zeros -fno-trapping-math)
> is the cause of the performance regression in the code generated for
> induct.f90 for gcc 4.3.1 on Macintel.

So you see the same complaint about -fassociative-math as I.
In the spirit of flogging a dead horse,  I'll remind again that 
-ffast-math and -fassociative-math are supposed to enable dot_product 
vectorization.  So, how does your vectorization report for the regression 
case look?
tim@tim-t61:~/src/ph> gfortran -O3 -ftree-vectorizer-verbose=1 -ffast-math 
induct.f90

induct.f90:5761: note:
induct.f90:5142: note:
induct.f90:777: note:
induct.f90:5062: note: LOOP VECTORIZED.
induct.f90:5061: note: LOOP VECTORIZED.
induct.f90:5060: note: LOOP VECTORIZED.
induct.f90:5059: note: LOOP VECTORIZED.
induct.f90:5058: note: LOOP VECTORIZED.
induct.f90:5057: note: LOOP VECTORIZED.
induct.f90:4893: note: vectorizing stmts using SLP.
induct.f90:4893: note: LOOP VECTORIZED.
induct.f90:4840: note: vectorized 7 loops in function.

induct.f90:3566: note:
induct.f90:3566: note:
induct.f90:3289: note:
induct.f90:3141: note:
induct.f90:2220: note: LOOP VECTORIZED.
induct.f90:2159: note: vectorizing stmts using SLP.
induct.f90:2159: note: LOOP VECTORIZED.
induct.f90:2077: note: LOOP VECTORIZED.
induct.f90:2016: note: vectorizing stmts using SLP.
induct.f90:2016: note: LOOP VECTORIZED.
induct.f90:1824: note: vectorized 4 loops in function.

induct.f90:1772: note: LOOP VECTORIZED.
induct.f90:1741: note: vectorizing stmts using SLP.
induct.f90:1741: note: LOOP VECTORIZED.
induct.f90:1660: note: LOOP VECTORIZED.
induct.f90:1629: note: vectorizing stmts using SLP.
induct.f90:1629: note: LOOP VECTORIZED.
induct.f90:1441: note: vectorized 4 loops in function.

induct.f90:1264: note:
induct.f90:1000: note:
induct.f90:556: note:
induct.f90:3060: note: LOOP VECTORIZED.
induct.f90:3038: note: vectorizing stmts using SLP.
induct.f90:3038: note: LOOP VECTORIZED.
induct.f90:2918: note: LOOP VECTORIZED.
induct.f90:2896: note: vectorizing stmts using SLP.
induct.f90:2896: note: LOOP VECTORIZED.
induct.f90:2845: note: created 1 versioning for alias checks.

induct.f90:2845: note: vectorizing stmts using SLP.
induct.f90:2845: note: LOOP VECTORIZED.
induct.f90:2724: note: LOOP VECTORIZED.
induct.f90:2702: note: vectorizing stmts using SLP.
induct.f90:2702: note: LOOP VECTORIZED.
induct.f90:2582: note: LOOP VECTORIZED.
induct.f90:2560: note: vectorizing stmts using SLP.
induct.f90:2560: note: LOOP VECTORIZED.
induct.f90:2509: note: created 1 versioning for alias checks.

induct.f90:2509: note: vectorizing stmts using SLP.
induct.f90:2509: note: LOOP VECTORIZED.
induct.f90:2273: note: vectorized 10 loops in function.
....
cpu time to define res-q can/coil mutual inductances =  37.183
....
run on Core 2 Duo laptop 2.001Ghz
Target: x86_64-unknown-linux-gnu
Configured with: ../configure --prefix=/usr/local/gcc44 
--enable-languages='c c++ fortran'
Thread model: posix
gcc version 4.4.0 20080509 (experimental) (GCC)

Does anyone care about -ffast-math performance of induct.f90 for gfortran 
4.3.x, when it never approached the performance of gfortran 4.4?