On 12/17/24 8:27 AM, Robin Dapp wrote:
Hi,
in PR117682 we build an interleaving pattern
{ 1, 201, 209, 25, 161, 105, 113, 185, 65, 9,
17, 89, 225, 169, 177, 249, 129, 73, 81, 153,
33, 233, 241, 57, 193, 137, 145, 217, 97, 41,
49, 121 };
with negative step expecting wraparound semantics due to -fwrapv.
For building interleaved patterns we have an optimization that
does e.g.
{1, 209, ...} = { 1, 0, 209, 0, ...}
and
{201, 25, ...} >> 8 = { 0, 201, 0, 25, ...}
and IORs those.
The optimization only works if the lowpart bits are zero. When
overflowing e.g. with a negative step we cannot guarantee this.
This patch makes us fall back to the generic merge handling for negative
steps.
I'm not 100% certain we're good even for positive steps. If the
step or the vector length is large enough we'd still overflow and
have non-zero lower bits. I haven't seen this happen during my
testing, though and the patch doesn't make things worse, so...
Regtested on rv64gcv_zvl512b. Let's see what the CI says.
Regards
Robin
PR target/117682
gcc/ChangeLog:
* config/riscv/riscv-v.cc (expand_const_vector): Fall back to
merging if either step is negative.
gcc/testsuite/ChangeLog:
* gcc.target/riscv/rvv/autovec/pr117682.c: New test.
Pre-commit testing showed a build failure. No really useful error
messages in the log and I'm not 100% convinced its your patch.
g++ -fno-PIE -c -g -O2 -DIN_GCC -DCROSS_DIRECTORY_STRUCTURE
-fno-exceptions -fno-rtti -fasynchronous-unwind-tables -W -Wall
-Wno-error=narrowing -Wwrite-strings -Wcast-qual -Wmissing-format-attribute
-Wconditionally-supported -Woverloaded-virtual -pedantic -Wno-long-long
-Wno-variadic-macros -Wno-overlength-strings -DHAVE_CONFIG_H -fno-PIE -I. -I.
-I../../../gcc/gcc -I../../../gcc/gcc/. -I../../../gcc/gcc/../include
-I../../../gcc/gcc/../libcpp/include -I../../../gcc/gcc/../libcody
-I../../../gcc/gcc/../libdecnumber -I../../../gcc/gcc/../libdecnumber/dpd
-I../libdecnumber -I../../../gcc/gcc/../libbacktrace -o gimple-match-4.o -MT
gimple-match-4.o -MMD -MP -MF ./.deps/gimple-match-4.TPo gimple-match-4.cc
make[2]: Leaving directory
'/home/runner/work/gcc-precommit-ci/gcc-precommit-ci/riscv-gnu-toolchain/build/build-gcc-linux-stage1/gcc'
g++: fatal error: Killed signal terminated program cc1plus
compilation terminated.
make[2]: *** [Makefile:1208: gimple-match-4.o] Error 1
Note how we didn't get a backtrace. Hard to know if it's really your
patch or not given the lack of data here.
jeff
