[llvm-bugs] [Bug 32997] New: [Polly - AST Generation] Use != for upper loop bound
llvm-bugs at lists.llvm.org
Wed May 10 23:32:31 PDT 2017
Bug ID: 32997
Summary: [Polly - AST Generation] Use != for upper loop bound
Assignee: polly-dev at googlegroups.com
Reporter: tobias at grosser.es
CC: llvm-bugs at lists.llvm.org
Currently the isl AST generator derives
for (long i = LB; i <= UB; i++)
for most loops. An alternative would be to generate
for (long i = LB; i != UB + 1; i++)
In the second version a value of LB that is strictly larger than UB + 1 will
cause i to eventually overflow. As we know this is not valid (and we annotate i
in Polly with NSW), the IR carries the information that such an overflow can
and consequently that LB must be smaller or equal to UB + 1.
LLVM and its -indvars pass prefers the second alternative precisely for this
We should consider to generate IR with the above type.
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