Reland [VPlan] Expand WidenInt inductions with nuw/nsw (#168354)

Changes: The previous patch had to be reverted to a mismatching-OpType
assert in cse. The reduced-test has now been added corresponding to a
RVV pointer-induction, and the pointer-induction case has been updated
to use createOverflowingBinaryOp.

While at it, record VPIRFlags in VPWidenInductionRecipe.

1 files changed, 12 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index cbfbc29360b0..10bd6cd47115 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7639,6 +7639,10 @@ createWidenInductionRecipes(VPInstruction *PhiR,
   assert(Plan.getLiveIn(IndDesc.getStartValue()) == Start &&
          "Start VPValue must match IndDesc's start value");
 
+  // It is always safe to copy over the NoWrap and FastMath flags. In
+  // particular, when folding tail by masking, the masked-off lanes are never
+  // used, so it is safe.
+  VPIRFlags Flags = vputils::getFlagsFromIndDesc(IndDesc);
   VPValue *Step =
       vputils::getOrCreateVPValueForSCEVExpr(Plan, IndDesc.getStep());
 
@@ -7651,7 +7655,7 @@ createWidenInductionRecipes(VPInstruction *PhiR,
 
   PHINode *Phi = cast<PHINode>(PhiR->getUnderlyingInstr());
   return new VPWidenIntOrFpInductionRecipe(Phi, Start, Step, &Plan.getVF(),
-                                           IndDesc, PhiR->getDebugLoc());
+                                           IndDesc, Flags, PhiR->getDebugLoc());
 }
 
 VPHeaderPHIRecipe *
@@ -7705,10 +7709,15 @@ VPRecipeBuilder::tryToOptimizeInductionTruncate(VPInstruction *VPI,
   PHINode *Phi = WidenIV->getPHINode();
   VPValue *Start = WidenIV->getStartValue();
   const InductionDescriptor &IndDesc = WidenIV->getInductionDescriptor();
+
+  // It is always safe to copy over the NoWrap and FastMath flags. In
+  // particular, when folding tail by masking, the masked-off lanes are never
+  // used, so it is safe.
+  VPIRFlags Flags = vputils::getFlagsFromIndDesc(IndDesc);
   VPValue *Step =
       vputils::getOrCreateVPValueForSCEVExpr(Plan, IndDesc.getStep());
-  return new VPWidenIntOrFpInductionRecipe(Phi, Start, Step, &Plan.getVF(),
-                                           IndDesc, I, VPI->getDebugLoc());
+  return new VPWidenIntOrFpInductionRecipe(
+      Phi, Start, Step, &Plan.getVF(), IndDesc, I, Flags, VPI->getDebugLoc());
 }
 
 VPSingleDefRecipe *VPRecipeBuilder::tryToWidenCall(VPInstruction *VPI,