[clang] [flang] [libc] [libcxx] [lld] [lldb] [llvm] [mlir] [LV] Vectorize maxnum/minnum w/o fast-math flags. (PR #148239)

[Florian Hahn via cfe-commits]

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@@ -652,3 +652,146 @@ void VPlanTransforms::attachCheckBlock(VPlan &Plan, Value *Cond,
     Term->addMetadata(LLVMContext::MD_prof, BranchWeights);
   }
 }
+
+bool VPlanTransforms::handleMaxMinNumReductionsWithoutFastMath(VPlan &Plan) {
+  VPRegionBlock *LoopRegion = Plan.getVectorLoopRegion();
+  VPReductionPHIRecipe *RedPhiR = nullptr;
+  bool HasUnsupportedPhi = false;
+
+  auto GetMinMaxCompareValue = [](VPReductionPHIRecipe *RedPhiR) -> VPValue * {
+    auto *MinMaxR = dyn_cast<VPRecipeWithIRFlags>(
+        RedPhiR->getBackedgeValue()->getDefiningRecipe());
+    if (!MinMaxR)
+      return nullptr;
+
+    auto *RepR = dyn_cast<VPReplicateRecipe>(MinMaxR);
+    if (!isa<VPWidenIntrinsicRecipe>(MinMaxR) &&
+        !(RepR && (isa<IntrinsicInst>(RepR->getUnderlyingInstr()))))
+      return nullptr;
+
+#ifndef NDEBUG
+    Intrinsic::ID RdxIntrinsicId =
+        RedPhiR->getRecurrenceKind() == RecurKind::FMaxNum ? Intrinsic::maxnum
+                                                           : Intrinsic::minnum;
+    assert((isa<VPWidenIntrinsicRecipe>(MinMaxR) &&
+            cast<VPWidenIntrinsicRecipe>(MinMaxR)->getVectorIntrinsicID() ==
+                RdxIntrinsicId) ||
+           (RepR &&
+            cast<IntrinsicInst>(RepR->getUnderlyingInstr())->getIntrinsicID() ==
+                RdxIntrinsicId) &&
+               "Intrinsic did not match recurrence kind");
+#endif
+
+    if (MinMaxR->getOperand(0) == RedPhiR)
+      return MinMaxR->getOperand(1);
+
+    assert(MinMaxR->getOperand(1) == RedPhiR &&
+           "Reduction phi operand expected");
+    return MinMaxR->getOperand(0);
+  };
+
+  for (auto &R : LoopRegion->getEntryBasicBlock()->phis()) {
+    // TODO: Also support fixed-order recurrence phis.
+    HasUnsupportedPhi |=
+        !isa<VPCanonicalIVPHIRecipe, VPWidenIntOrFpInductionRecipe,
+             VPReductionPHIRecipe>(&R);
+    auto *Cur = dyn_cast<VPReductionPHIRecipe>(&R);
+    if (!Cur)
+      continue;
----------------
fhahn wrote:

Updated thanks!

https://github.com/llvm/llvm-project/pull/148239