Arnold Schwaighofer
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f9cea17f75
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LoopVectorizer: integer division is not a reduction operation
Don't classify idiv/udiv as a reduction operation. Integer division is lossy.
For example : (1 / 2) * 4 != 4/2.
Example:
int a[] = { 2, 5, 2, 2}
int x = 80;
for()
x /= a[i];
Scalar:
x /= 2 // = 40
x /= 5 // = 8
x /= 2 // = 4
x /= 2 // = 2
Vectorized:
<80, 1> / <2,5> //= <40,0>
<40, 0> / <2,2> //= <20,0>
20*0 = 0
radar://13640654
llvm-svn: 179381
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2013-04-12 15:15:19 +00:00 |