[InstCombine] Folding of shifts by the sum of positive values
This patch introduces the combine:
(C1 shift (A add C2)) -> ((C1 shift C2) shift A)
iff A and C2 are both positive
If both A and C2 are know to be positive then we can safely split into 2 shifts, permitting the folding of the Inner shift.
Fix for the spec benchmark case mentioned by @nadav on PR15141 (assuming we can prove that the inputs as positive).
Differential Revision: https://reviews.llvm.org/D26000
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285696 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed