[ARM] isTruncateFree fix

I implemented isTruncateFree in rL313533, this patch fixes the logic
to match my comment, as the previous logic was too general. Now the
only truncates that are free are i64 -> i32.

Differential Revision: https://reviews.llvm.org/D38234


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@314280 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed