[PATCH] D40633: [PCG] Poor shuffle lane tracking (PR35454 )

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


================
Comment at: lib/Transforms/InstCombine/InstructionCombining.cpp:1465-1466
+  // recompute the shuffle instruction mask has very limited usage because, we
+  // can recompute the shuffle mask only in a case when the shuffle mask is a
+  // constant value, and secondly we can do this only in a situation when we
+  // need to change a shuffle instruction vector type from <4 x i32> to <16 x
----------------
The shuffle mask is always a constant:
"The shuffle mask operand is required to be a constant vector with either constant integer or undef values."
http://llvm.org/docs/LangRef.html#shufflevector-instruction


https://reviews.llvm.org/D40633