On Fri, 2019-12-06 at 14:05 +0000, Sudakshina Das wrote: > Hi > > While looking at the vectorization for following example, we > realized > that even though vectorizable_shift function was distinguishing > vector > shifted by vector from vector shifted by scalar, while modeling the > cost > it would always add the cost of building a vector constant despite > not > needing it for vector shifted by scalar. > > This patch fixes this by using scalar_shift_arg to determine whether > we > need to build a vector for the second operand or not. This reduces > prologue cost as shown in the test. > > Build and regression tests pass on aarch64-none-elf and > x86_64-pc-linux-gnu-gcc. This gives a 3.42% boost to 525.x264_r in > Spec2017 for AArch64. > > gcc/ChangeLog: > > 2019-xx-xx Sudakshina Das <sudi....@arm.com> > Richard Sandiford <richard.sandif...@arm.com> > > * tree-vect-stmt.c (vectorizable_shift): Condition ndts for > vect_model_simple_cost call on scalar_shift_arg. > > gcc/testsuite/ChangeLog: > > 2019-xx-xx Sudakshina Das <sudi....@arm.com> > > * gcc.dg/vect/vect-shift-5.c: New test. It's a bit borderline, but it's really just twiddling a cost, so OK.
jeff
