Re: [PATCH] adjust vectorization expectations for ppc costmodel 76b

[Alexandre Oliva <oliva@adacore.com>]

On May 23, 2024, Alexandre Oliva <oliva@adacore.com> wrote:

> On Apr 29, 2024, "Kewen.Lin" <linkw@linux.ibm.com> wrote:
>> I think you can still push the patch as the testing just exposes
>> another issue.

> ACK, thanks, I've just confirmed that the problem I reported on
> ppc64el-linux-gnu didn't come up when testing on ppc64-vx7r2 with a
> non-power8 emulated cpu, so I'm going to install it.

I see I hadn't posted the latest version of the patch, with the updated
attribution and commit message.  Here it is.  I'm checking it in.

testsuite: adjust iteration count for ppc costmodel 76b

From: Alexandre Oliva <oliva@adacore.com>

For some hardware which doesn't support unaligned vector memory access,
test case costmodel-vect-76b.c expects to see cost modeling would make
the decision that it's not profitable for peeling, according to the
commit history, test case comments and the way to check.

For now, the existing loop bound 14 works well for Power7, but it does
not for some targets on which the cost of operation vec_perm can be
different from Power7, such as: Power6, it's 3 vs. 1.  This difference
further causes the difference (10 vs. 12) on the minimum iteration for
profitability and cause the failure.  To keep the original test point,
this patch is to tweak the loop bound to ensure it's not profitable
to be vectorized for !vect_no_align with peeling.


Co-Authored-By: Kewen Lin <linkw@linux.ibm.com>

for  gcc/testsuite/ChangeLog

	* gcc.dg/vect/costmodel/ppc/costmodel-vect-76b.c (N): Tweak.
---
 .../gcc.dg/vect/costmodel/ppc/costmodel-vect-76b.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/vect/costmodel/ppc/costmodel-vect-76b.c b/gcc/testsuite/gcc.dg/vect/costmodel/ppc/costmodel-vect-76b.c
index cbbfbb24658f8..e48b0ab759e75 100644
--- a/gcc/testsuite/gcc.dg/vect/costmodel/ppc/costmodel-vect-76b.c
+++ b/gcc/testsuite/gcc.dg/vect/costmodel/ppc/costmodel-vect-76b.c
@@ -6,7 +6,7 @@
 
 /* On Power7 without misalign vector support, this case is to check it's not
    profitable to perform vectorization by peeling to align the store.  */
-#define N 14
+#define N 13
 #define OFF 4
 
 /* Check handling of accesses for which the "initial condition" -


-- 
Alexandre Oliva, happy hacker            https://FSFLA.org/blogs/lxo/
   Free Software Activist                   GNU Toolchain Engineer
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