[VP] vp intrinsics are not speculatable

VP intrinsics show UB if the %evl parameter is out of bounds - they must
not carry the speculatable attribute.  The out-of-bounds UB disappears
when the %evl parameter is expanded into the mask or expansion replaces
the entire VP intrinsic with non-VP code.

This patch
- Removes the speculatable attribute on all VP intrinsics.
- Generalizes the isSafeToSpeculativelyExecute function to let VP
  expansion know whether the VP intrinsic replacement will be
  speculatable.  VP expansion may only discard %evl where this is the
  case.

Reviewed By: frasercrmck

Differential Revision: https://reviews.llvm.org/D125296

1 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/ExpandVectorPredication.cpp b/llvm/lib/CodeGen/ExpandVectorPredication.cpp
index aa52914..fbb89a7 100644
--- a/llvm/lib/CodeGen/ExpandVectorPredication.cpp
+++ b/llvm/lib/CodeGen/ExpandVectorPredication.cpp
@@ -118,10 +118,10 @@ static bool maySpeculateLanes(VPIntrinsic &VPI) {
   if (isa<VPReductionIntrinsic>(VPI))
     return false;
   // Fallback to whether the intrinsic is speculatable.
-  // FIXME: Check whether the replacing non-VP code will be speculatable
-  //        instead. VP intrinsics themselves are never speculatable because of
-  //        UB if %evl is greater than the runtime vector length.
-  return isSafeToSpeculativelyExecute(cast<Operator>(&VPI));
+  Optional<unsigned> OpcOpt = VPI.getFunctionalOpcode();
+  unsigned FunctionalOpc = OpcOpt.getValueOr((unsigned)Instruction::Call);
+  return isSafeToSpeculativelyExecuteWithOpcode(FunctionalOpc,
+                                                cast<Operator>(&VPI));
 }
 
 //// } Helpers
@@ -481,7 +481,7 @@ struct TransformJob {
 };
 
 void sanitizeStrategy(VPIntrinsic &VPI, VPLegalization &LegalizeStrat) {
-  // Speculatable instructions do not strictly need predication.
+  // Operations with speculatable lanes do not strictly need predication.
   if (maySpeculateLanes(VPI)) {
     // Converting a speculatable VP intrinsic means dropping %mask and %evl.
     // No need to expand %evl into the %mask only to ignore that code.