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Author SHA1 Message Date
Ulrich Weigand 4a4d4ab7a4 [SystemZ] Fix wrong-code generation for certain always-false conditions
We've found another bug in the code generation logic conditions for a
certain class of always-false conditions, those of the form
   if ((a & 1) < 0)

These only reach the back end when compiling without optimization.

The bug was introduced by the choice of using TEST UNDER MASK
to implement a check for
   if ((a & MASK) < VAL)
as
   if ((a & MASK) == 0)

where VAL is less than the the lowest bit of MASK.  This is correct
in all cases except for VAL == 0, in which case the original
condition is always false, but the replacement isn't.

Fixed by excluding that particular case.

llvm-svn: 259381
2016-02-01 18:31:19 +00:00