[PATCH] D13757: [x86] promote 'add nsw' to a wider type to allow more combines

[Zia Ansari via llvm-commits]

zansari added a comment.

Just another +1 on Quentin's comment regarding it being nice to see fewer extends in DAGCombine to expose more opportunities.

Given the explained complexity with that, these changes seem reasonable, to me. Just made one small comment/comment.

Thanks,
Zia.


================
Comment at: lib/Target/X86/X86ISelLowering.cpp:25702
@@ +25701,3 @@
+  // Don't make the 'add' bigger if there's no hope of combining it with some
+  // other 'add' or 'shl' instruction.
+  // TODO: It may be profitable to generate simpler LEA instructions in place
----------------
How about also SUB instructions to catch the simple constant merging case, similar to the one in add_nsw_consts?


http://reviews.llvm.org/D13757