[PATCH] D34077: DAGCombine: Combine BUILD_VECTOR to TRUNCATE

[Zvi Rackover via Phabricator via llvm-commits]

zvi added a comment.

Right now this patch is not good for ARM, so here are the options:

1. Try to improve the ARM backend
2. Add a TLI hook for allowing the target to bail out
3. Do this only in the X86 lowering

I will start with checking the feasibility of  option 1.



================
Comment at: test/CodeGen/ARM/vpadd.ll:221
 ; CHECK-NEXT:    vld1.64 {d16, d17}, [r0]
-; CHECK-NEXT:    vpadd.i8 d16, d16, d17
+; CHECK-NEXT:    vorr d18, d16, d16
+; CHECK-NEXT:    vorr d19, d17, d17
----------------
This may be a similar issue to https://reviews.llvm.org/D32993#inline-286079.
Will look into this.


https://reviews.llvm.org/D34077