[PATCH] D46957: [x86] Lower some trunc + shuffle patterns to vpmov[q|d][b|w]

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


================
Comment at: lib/Target/X86/X86ISelLowering.cpp:9418
+    // These should refer to the second vectors elements
+    while (I < N) {
+      if (Mask[I] != Size + I * delta)
----------------
RKSimon wrote:
> Can you use the shuffle mask helpers for any/all of these - isUndefOrInRange etc?
If you tweak isSequentialOrUndefInRange to take an increment argument (default = 1) then you could remove this loop.


================
Comment at: lib/Target/X86/X86ISelLowering.cpp:9429
+  while (I < Size) {
+    if (isInRange(Mask[I], TruncatedVectorStart, TruncatedVectorStart + Size))
+      return false;
----------------
GBuella wrote:
> RKSimon wrote:
> > Why can't you permit UNDEFs in the shuffle mask?
> I do permit undef here. The condition of the branch is what I don't permit.
Then why don't you use isUndefOrZeroOrInRange()?
```
if (!isUndefOrZeroOrInRange(Mask.slice(Split, Size), TruncatedVectorStart, TruncatedVectorStart + Size))
  return false;
```


https://reviews.llvm.org/D46957