Torok Edwin 99b1003c2e Fix PR4254.
The DAGCombiner created a negative shiftamount, stored in an
unsigned variable. Later the optimizer eliminated the shift entirely as being
undefined.
Example: (srl (shl X, 56) 48). ShiftAmt is 4294967288.
Fix it by checking that the shiftamount is positive, and storing in a signed
variable.

llvm-svn: 72331
2009-05-23 17:29:48 +00:00
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2009-05-23 17:29:48 +00:00
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