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git.ipfire.org Git - thirdparty/gcc.git/commit
middle-end: simplify complex if expressions where comparisons are inverse of one another.
This optimizes the following sequence
((a < b) & c) | ((a >= b) & d)
into
(a < b ? c : d) & 1
for scalar and on vector we can omit the & 1.
Also recognizes
(-(a < b) & c) | (-(a >= b) & d)
into
a < b ? c : d
This changes the code generation from
zoo2:
cmp w0, w1
cset w0, lt
cset w1, ge
and w0, w0, w2
and w1, w1, w3
orr w0, w0, w1
ret
into
cmp w0, w1
csel w0, w2, w3, lt
and w0, w0, 1
ret
and significantly reduces the number of selects we have to do in the vector
code.
gcc/ChangeLog:
* match.pd: Add new rule.
gcc/testsuite/ChangeLog:
* gcc.target/aarch64/if-compare_1.c: New test.
* gcc.target/aarch64/if-compare_2.c: New test.