[llvm] [IVDescriptors][NFC] Remove the number check of cmp select pattern for min/max reduction. (PR #118943)

[Mel Chen via llvm-commits]

https://github.com/Mel-Chen created https://github.com/llvm/llvm-project/pull/118943

In RecurrenceDescriptor::isMinMaxPattern, only cmp-select patterns that match the form select(cmp(X, Y), X, Y) are recognized as min/max patterns. This ensures that both the cmp and select instructions are visited, eliminating the need for confirmation via NumCmpSelectPatternInst.

>From e6bb1c4d2c1c4d581797a3b1657c3c7dac1c2289 Mon Sep 17 00:00:00 2001
From: Mel Chen <mel.chen at sifive.com>
Date: Thu, 5 Dec 2024 23:41:48 -0800
Subject: [PATCH] [IVDescriptors][NFC] Remove the number check of cmp select
 pattern for min/max reduction.

---
 llvm/lib/Analysis/IVDescriptors.cpp | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/llvm/lib/Analysis/IVDescriptors.cpp b/llvm/lib/Analysis/IVDescriptors.cpp
index e1eb219cf977e1..27ba1dd9f9e047 100644
--- a/llvm/lib/Analysis/IVDescriptors.cpp
+++ b/llvm/lib/Analysis/IVDescriptors.cpp
@@ -244,9 +244,9 @@ bool RecurrenceDescriptor::AddReductionVar(
   // must include the original PHI.
   bool FoundStartPHI = false;
 
-  // To recognize min/max patterns formed by a icmp select sequence, we store
-  // the number of instruction we saw from the recognized min/max pattern,
-  //  to make sure we only see exactly the two instructions.
+  // Tracks the number of instructions (either cmp or select) observed in an
+  // AnyOf recurrence pattern to ensure it matches the expected instruction
+  // sequence.
   unsigned NumCmpSelectPatternInst = 0;
   InstDesc ReduxDesc(false, nullptr);
 
@@ -415,11 +415,9 @@ bool RecurrenceDescriptor::AddReductionVar(
     if (IsAPhi && Cur != Phi && !areAllUsesIn(Cur, VisitedInsts))
       return false;
 
-    if ((isIntMinMaxRecurrenceKind(Kind) || Kind == RecurKind::IAnyOf) &&
-        (isa<ICmpInst>(Cur) || isa<SelectInst>(Cur)))
+    if (Kind == RecurKind::IAnyOf && isa<ICmpInst, SelectInst>(Cur))
       ++NumCmpSelectPatternInst;
-    if ((isFPMinMaxRecurrenceKind(Kind) || Kind == RecurKind::FAnyOf) &&
-        (isa<FCmpInst>(Cur) || isa<SelectInst>(Cur)))
+    if (Kind == RecurKind::FAnyOf && isa<FCmpInst, SelectInst>(Cur))
       ++NumCmpSelectPatternInst;
 
     // Check  whether we found a reduction operator.
@@ -497,13 +495,6 @@ bool RecurrenceDescriptor::AddReductionVar(
     Worklist.append(NonPHIs.begin(), NonPHIs.end());
   }
 
-  // This means we have seen one but not the other instruction of the
-  // pattern or more than just a select and cmp. Zero implies that we saw a
-  // llvm.min/max intrinsic, which is always OK.
-  if (isMinMaxRecurrenceKind(Kind) && NumCmpSelectPatternInst != 2 &&
-      NumCmpSelectPatternInst != 0)
-    return false;
-
   if (isAnyOfRecurrenceKind(Kind) && NumCmpSelectPatternInst != 1)
     return false;