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Subject: [Bug tree-optimization/66280] [4.8/4.9 Regression]  ICE: in vect_get_vec_def_for_operand, at tree-vect-stmts.c:1472
Date: Tue, 16 Jun 2015 13:10:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66280

--- Comment #14 from Richard Biener <rguenth at gcc dot gnu.org> ---
Backporting the fix from comment#8 to the 4.9 branch makes us run into PR64829.

spawn /home/abuild/rguenther/gcc49-g/gcc/xgcc
-B/home/abuild/rguenther/gcc49-g/gcc/
/space/rguenther/src/svn/gcc-4_9-branch/gcc/testsuite/gcc.dg/vect/slp-widen-mult-half.c
-fno-diagnostics-show-caret -fdiagnostics-color=never -msse2 -ftree-vectorize
-fno-vect-cost-model -fno-common -O2 -fdump-tree-vect-details -lm -march=native
-o ./slp-widen-mult-half.exe^M
/space/rguenther/src/svn/gcc-4_9-branch/gcc/testsuite/gcc.dg/vect/slp-widen-mult-half.c:
In function 'foo':^M
/space/rguenther/src/svn/gcc-4_9-branch/gcc/testsuite/gcc.dg/vect/slp-widen-mult-half.c:15:1:
internal compiler error: in vect_detect_hybrid_slp_stmts, at
tree-vect-slp.c:1790^M
0xdff124 vect_detect_hybrid_slp_stmts^M
        /space/rguenther/src/svn/gcc-4_9-branch/gcc/tree-vect-slp.c:1790^M
0xdff2d7 vect_detect_hybrid_slp_stmts^M
        /space/rguenther/src/svn/gcc-4_9-branch/gcc/tree-vect-slp.c:1815^M
0xdff2d7 vect_detect_hybrid_slp_stmts^M

...

while we could simply remove the assert from the backport I think that is
not a good idea (well, strictly speaking we need to adjust the stmt walking
for that "bug")

Backporting the fix for PR64829 is non-trivial due to unrelated changes.

So I am at the moment not considering backports to 4.9 (and it's too late for
4.8).