[Bug middle-end/64448] New: New middle-end pattern breaks vector BIF folding on AArch64.
belagod at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Tue Dec 30 18:12:00 GMT 2014
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64448
Bug ID: 64448
Summary: New middle-end pattern breaks vector BIF folding on
AArch64.
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: belagod at gcc dot gnu.org
This new pattern
Author: mpolacek <mpolacek@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Wed Dec 17 11:48:33 2014 +0000
PR middle-end/63568
match.pd: Add (x & ~m) | (y & m) -> ((x ^ y) & m) ^ x pattern.
gcc.dg/pr63568.c: New test.
breaks BSL folding to a BIF on AArch64.
Causes this regression:
FAIL: gcc.target/aarch64/vbslq_u64_1.c scan-assembler-times bif\\tv 1
The code now generated is:
vbslq_dummy_u32:
eor v0.16b, v1.16b, v0.16b
and v0.16b, v0.16b, v2.16b
eor v0.16b, v1.16b, v0.16b
ret
.size vbslq_dummy_u32, .-vbslq_dummy_
instead of:
vbslq_dummy_u32:
bif v0.16b, v1.16b, v2.16b
ret
.size vbslq_dummy_u32, .-vbslq_dummy_u32
Optimized tree when folding happens:
vbslq_dummy_u32 (uint32x4_t a, uint32x4_t b, uint32x4_t mask)
{
__Uint32x4_t _3;
__Uint32x4_t _4;
__Uint32x4_t _6;
uint32x4_t _7;
<bb 2>:
_3 = mask_1(D) & a_2(D);
_4 = ~mask_1(D);
_6 = _4 & b_5(D);
_7 = _3 | _6;
return _7;
}
Optimized tree where folding does not happen:
vbslq_dummy_u32 (uint32x4_t a, uint32x4_t b, uint32x4_t mask)
{
__Uint32x4_t _3;
__Uint32x4_t _5;
uint32x4_t _6;
<bb 2>:
_3 = b_1(D) ^ a_2(D);
_5 = _3 & mask_4(D);
_6 = b_1(D) ^ _5;
return _6;
}
This will probably need another idiom to be caught by the BSL -> BIF folder.
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