[SCEVExpand] do not hoist divisions by zero (PR30935)

SCEVExpand computes the insertion point for the components of a SCEV to be code
generated.  When it comes to generating code for a division, SCEVexpand would
not be able to check (at compilation time) all the conditions necessary to avoid
a division by zero.  The patch disables hoisting of expressions containing
divisions by anything other than non-zero constants in order to avoid hoisting
these expressions past conditions that should hold before doing the division.

The patch passes check-all on x86_64-linux.

Differential Revision: https://reviews.llvm.org/D27216

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289412 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed