[IVDescriptors] Identify min/max recurrences in single pass.

This patch ties to extend the approach from
llvm#141431 to all min/max
recurrence kinds.

This patch adds a new getMinMaxRecurrence that identifies all min/max
recurrences in a single pass. It starts at the backedge value of a phi
and tries to identify the kind of the min/max recurrences.

It then walks from the backedge value to its operands recursively until
it reaches out-of-loop values or the phi.

Then users of both the backedge value and all instructions in the chain
from backedge value to phi are checked.

This consolidates all logic to identify min/max recurrences to a single
function, and avoids the need to try to identify each min/max reduction
kind individually.

Author: fhahn

llvm/include/llvm/Analysis/IVDescriptors.h

@@ -155,14 +155,6 @@ class RecurrenceDescriptor {
   LLVM_ABI static bool areAllUsesIn(Instruction *I,
                                     SmallPtrSetImpl<Instruction *> &Set);
 
-  /// Returns a struct describing if the instruction is a llvm.(s/u)(min/max),
-  /// llvm.minnum/maxnum or a Select(ICmp(X, Y), X, Y) pair of instructions
-  /// corresponding to a min(X, Y) or max(X, Y), matching the recurrence kind \p
-  /// Kind. \p Prev specifies the description of an already processed select
-  /// instruction, so its corresponding cmp can be matched to it.
-  LLVM_ABI static InstDesc isMinMaxPattern(Instruction *I, RecurKind Kind,
-                                           const InstDesc &Prev);
-
   /// Returns a struct describing whether the instruction is either a
   ///   Select(ICmp(A, B), X, Y), or
   ///   Select(FCmp(A, B), X, Y)