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On 15/12/17 11:57, Sudakshina Das wrote:
Hi
This patch fixes the inconsistent behavior observed at -O3 for the
unordered comparisons. According to the online docs
(https://gcc.gnu.org/onlinedocs/gcc-7.2.0/gccint/Unary-and-Binary-Expressions.html),
all of the following should not raise an FP exception:
- UNGE_EXPR
- UNGT_EXPR
- UNLE_EXPR
- UNLT_EXPR
- UNEQ_EXPR
Also ORDERED_EXPR and UNORDERED_EXPR should only return zero or one.
The aarch64-simd.md handling of these were generating exception raising
instructions such as fcmgt. This patch changes the instructions that are
emitted to in order to not give out the exceptions. We first check each
operand for NaNs and force any elements containing NaN to zero before
using them in the compare.
Example: UN<cc> (a, b) -> UNORDERED (a, b) | (cm<cc> (isnan (a) ? 0.0 :
a, isnan (b) ? 0.0 : b))
The ORDERED_EXPR is now handled as (cmeq (a, a) & cmeq (b, b)) and
UNORDERED_EXPR as ~ORDERED_EXPR and UNEQ as (~ORDERED_EXPR | cmeq (a,b)).
Testing done: Checked for regressions on bootstrapped
aarch64-none-linux-gnu and added a new test case.
Is this ok for trunk? This will probably need a back-port to
gcc-7-branch as well.
Thanks
Sudi
ChangeLog Entries:
*** gcc/ChangeLog ***
2017-12-15 Sudakshina Das <sudi....@arm.com>
PR target/81647
* config/aarch64/aarch64-simd.md (vec_cmp<mode><v_int_equiv>):
Modify instructions for
UNLT, UNLE, UNGT, UNGE, UNEQ, UNORDERED and ORDERED.
*** gcc/testsuite/ChangeLog ***
2017-12-15 Sudakshina Das <sudi....@arm.com>
PR target/81647
* gcc.target/aarch64/pr81647.c: New.
