Hi there, It seems from PR61320 that the bswap pass causes some problems when it replaces an OR expression by an unaligned access. Although it's not clear yet why the unaligned load does not go through the extract_bit_field codepath, it is necessary to provide a solution as this prevent sparc from bootstrapping. This patch takes the simple approach of cancelling the bswap optimization when the load that would replace the OR expression would be an unaligned load and the target has SLOW_UNALIGNED_ACCESS. In the long run this patch should be reverted as soon as the root cause of the current problem is found.
The patch also rewrite the test to take into account the fact that the
optimization is
not done for some target. It also add some alignment hint so that more tests
can be
run even on STRICT_ALIGNMENT targets.
ChangeLog changes are:
*** gcc/ChangeLog ***
2014-06-03 Thomas Preud'homme <thomas.preudho...@arm.com>
PR tree-optimization/61320
* tree-ssa-math-opts.c (bswap_replace): Cancel bswap optimization when
load is unaligned and would be slow for this target.
*** gcc/testsuite/ChangeLog ***
2014-06-03 Thomas Preud'homme <thomas.preudho...@arm.com>
* gcc.dg/optimize-bswaphi-1.c: Make variables global when possible to
enforce correct alignment and make the test work better on
STRICT_ALIGNMENT targets. Also adjust dg-final selectors when alignment
cannot be controlled (read_*_3 ()).
* gcc.dg/optimize-bswapsi-2.c: Likewise.
* gcc.dg/optimize-bswapdi-3.c: Likewise.
Bootstrapped on x86_64-linux-gnu and no regression found in the testsuite.
Patch is
in attachment. It applies on top of the one for PR61306 in the email titled
"[PATCH] Fix PR61306: improve handling of sign and cast in bswap" but can be
trivially modified to apply directly on trunk should that patch (PR61306) need
to be
improved.
Is this ok for trunk?
Best regards,
Thomas
PR61320.1.0.diff
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