[Bug tree-optimization/53773] New: Vectorizer generates non-canonical multiplies

["wschmidt at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53773

             Bug #: 53773
           Summary: Vectorizer generates non-canonical multiplies
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: wschmidt@gcc.gnu.org
                CC: bergner@vnet.ibm.com, rguenther@suse.de


There are two tests in the regression testsuite for which the vectorizer
generates GIMPLE multiplies that are not canonical.  Specifically, they
generate multiplies where rhs1 is a constant and rhs2 is an SSA name.  The two
tests are:

(1) gcc.dg/vect/pr50451.c
(2) gfortran.dg/pr17143.f90

For (1), the generated GIMPLE includes:

  integral_7 = 10 * integral_17;
  ...
  decimal_8 = 10 * decimal_18;

For (2):

  i.3_3 = 2 * prephitmp.9_23;

Probably best just to run these tests from the test suite to reproduce, but
here are the commands I used.

Example invocation for (1):

/home/wschmidt/gcc/build/gcc-mainline-slsrpt1a-debug/gcc/xgcc
-B/home/wschmidt/gcc/build/gcc-mainline-slsrpt1a-debug/gcc/
/home/wschmidt/gcc/gcc-mainline-slsrpt1a/gcc/testsuite/gcc.dg/vect/pr50451.c
-fno-diagnostics-show-caret -flto -maltivec -mvsx -mno-allow-movmisalign
-ftree-vectorize -fno-vect-cost-model -fno-common -O2 -fdump-tree-vect-details
-S -m64 -o pr50451.s

Example invocation for (2):

/home/wschmidt/gcc/install/gcc-mainline-slsrpt1a-debug/bin/gfortran
-B/home/wschmidt/gcc/build/gcc-mainline-slsrpt1a-debug/gcc/testsuite/gfortran3/../../
-B/home/wschmidt/gcc/build/gcc-mainline-slsrpt1a-debug/powerpc64-linux/32/libgfortran/
/home/wschmidt/gcc/gcc-mainline-slsrpt1a/gcc/testsuite/gfortran.dg/pr17143.f90
-fno-diagnostics-show-caret -O3 -fomit-frame-pointer -std=legacy
-B/home/wschmidt/gcc/build/gcc-mainline-slsrpt1a-debug/powerpc64-linux/32/libgfortran/.libs
-L/home/wschmidt/gcc/build/gcc-mainline-slsrpt1a-debug/powerpc64-linux/32/libgfortran/.libs
-L/home/wschmidt/gcc/build/gcc-mainline-slsrpt1a-debug/powerpc64-linux/32/libgfortran/.libs
-lm -m32 -o ./pr17143.exe