[Analysis][LV] Handle FMinNum/FMaxNum in RecurrenceDescriptor::getOpcode

[uyoyo0]

Modify RecurrenceDescriptor::getOpcode to handle RecurKind::FMinNum and RecurKind::FMaxNum by returning Instruction::FCmp, matching FMin/FMax.

Without these cases, querying the opcode for minNum/maxNum reductions can hit llvm_unreachable in code that inspects the recurrence kind. Also added IVDescriptorsTest.GetOpcodeForFMinMaxNum (gtest) to verify the mapping.

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[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: Uyiosa Iyekekpolor (uyoyo0)

Changes

Modify RecurrenceDescriptor::getOpcode to handle RecurKind::FMinNum and RecurKind::FMaxNum by returning Instruction::FCmp, matching FMin/FMax.

Without these cases, querying the opcode for minNum/maxNum reductions can hit llvm_unreachable in code that inspects the recurrence kind. Also added IVDescriptorsTest.GetOpcodeForFMinMaxNum (gtest) to verify the mapping.

---

Full diff: https://github.com/llvm/llvm-project/pull/152794.diff

2 Files Affected:

• (modified) llvm/lib/Analysis/IVDescriptors.cpp (+2)
• (modified) llvm/unittests/Analysis/IVDescriptorsTest.cpp (+9)

diff --git a/llvm/lib/Analysis/IVDescriptors.cpp b/llvm/lib/Analysis/IVDescriptors.cpp
index 8be5de3bf356f..efb6a5e97bc2b 100644
--- a/llvm/lib/Analysis/IVDescriptors.cpp
+++ b/llvm/lib/Analysis/IVDescriptors.cpp
@@ -1228,6 +1228,8 @@ unsigned RecurrenceDescriptor::getOpcode(RecurKind Kind) {
     return Instruction::ICmp;
   case RecurKind::FMax:
   case RecurKind::FMin:
+  case RecurKind::FMaxNum:
+  case RecurKind::FMinNum:
   case RecurKind::FMaximum:
   case RecurKind::FMinimum:
   case RecurKind::FMaximumNum:
diff --git a/llvm/unittests/Analysis/IVDescriptorsTest.cpp b/llvm/unittests/Analysis/IVDescriptorsTest.cpp
index 453800abf9cab..bc237296a36b1 100644
--- a/llvm/unittests/Analysis/IVDescriptorsTest.cpp
+++ b/llvm/unittests/Analysis/IVDescriptorsTest.cpp
@@ -259,3 +259,12 @@ for.end:
         EXPECT_EQ(Kind, RecurKind::FMax);
       });
 }
+
+TEST(IVDescriptorsTest, GetOpcodeForFMinMaxNum) {
+  using RK = RecurKind;
+  // Ensure the "num" variants map to the same opcode as the plain ones.
+  EXPECT_EQ(RecurrenceDescriptor::getOpcode(RK::FMinNum),
+    RecurrenceDescriptor::getOpcode(RK::FMin));
+  EXPECT_EQ(RecurrenceDescriptor::getOpcode(RK::FMinNum),
+    RecurrenceDescriptor::getOpcode(RK::FMin));
+}

[fhahn]

This is very likely to be incorrect.

There's not really a corresponding opcode and treating them the same as FMax/FMin will be incorrect. It would probably be better to update your code not to query getOpcode for those recurrence kinds.

[uyoyo0]

Thank you for the review and explanation.