[PATCH] D18701: [ARM] Adding IEEE-754 SIMD detection to loop vectorizer

[Ashutosh Nema via llvm-commits]

ashutosh.nema added inline comments.

================
Comment at: lib/Transforms/Vectorize/LoopVectorize.cpp:4714
@@ +4713,3 @@
+      // non-IEEE-754 compliant SIMD units.
+      } else if (it->getType()->isFloatingPointTy() &&
+                (it->isBinaryOp() || it->isCast()) &&
----------------
rengolin wrote:
> ashutosh.nema wrote:
> > You may want to set unsafe flag for some of the intrinsics as well.
> > i.e. intrinsic like minnum, maxnum are floating point unsafe and 
> > follows IEEE-754 semantics. 
> > 
> Hum, that's a good point.
> 
> But I don't want to be listing specific intrinsics if the list is not *very* short, or completely target independent.
> 
> Maybe I should just be safe and do that for all FP operations except move, load and store?
Doing this for all operations except move, load and store would be conservative, this might miss eligible cases for vectorization.

If we list, then list should be for the safe intrinsic(those can be vectorized) and for others will mark ‘setPotentiallyUnsafe’.

Also need to handle function which are later going to be mapped to intrinsic (i.e. fmax, fmaxf).

llvm::getIntrinsicIDForCall returns intrinsic ID for vectorizable CallInst, in case it does not found it returns not_intrinsic.

Probably you can write a wrapper around this function and check safety.

llvm::isTriviallyVectorizable has a list of vectorizable intrinsics, might help during listing.


http://reviews.llvm.org/D18701