[PATCH] D21330: Loop vectorization with FP induction variables

[Elena Demikhovsky via llvm-commits]

delena marked 3 inline comments as done.

================
Comment at: ../include/llvm/Transforms/Utils/LoopUtils.h:274
@@ -273,1 +273,3 @@
+    : StartValue(nullptr), IK(IK_NoInduction), Step(nullptr),
+    UnsafeAlgebraInst(nullptr), BinaryOp((Instruction::BinaryOps)0) {}
 
----------------
mkuper wrote:
> I think Instruction::BinaryOpsEnd may be better for an explicitly invalid BinaryOp. Not sure that's a good choice, but pretty sure 0 isn't.
Thanks, I'll fix.

================
Comment at: ../lib/Transforms/Vectorize/LoopVectorize.cpp:6405
@@ +6404,3 @@
+
+    // Floating point operations had to be 'fast' to enable the unrolling.
+    FastMathFlags Flags;
----------------
mkuper wrote:
> Are you sure about this? I mean, it's true for vectorizing, but is it true here as well?
> (I'm not saying it isn't, just making sure this is intentional)
Even if you have only unrolling, and VF is 1, the value of FP induction is calculated as:
 sitofp(PrimaryIV) * Increment.

  for (int i=0; i<N; i++) {
    fp_ind += fp_inc;
  }
is transferred to something like this:
  init = fp_inc;
  for (int i=0; i<N; i++) {
    fp_ind = init + i*fp_inc; 
  }
In this case we need unsafe math. 
I added tests for unrolling.


Repository:
  rL LLVM

https://reviews.llvm.org/D21330