[IR] Improve code in isIdenticalToWhenDefined (NFC) (llvm#151881)

Prefer llvm::equal() over std::equal().

Author: artagnon

llvm/lib/IR/Instruction.cpp

@@ -942,14 +942,13 @@ bool Instruction::isIdenticalToWhenDefined(const Instruction *I,
 
   // We have two instructions of identical opcode and #operands.  Check to see
   // if all operands are the same.
-  if (!std::equal(op_begin(), op_end(), I->op_begin()))
+  if (!equal(operands(), I->operands()))
     return false;
 
   // WARNING: this logic must be kept in sync with EliminateDuplicatePHINodes()!
-  if (const PHINode *thisPHI = dyn_cast<PHINode>(this)) {
-    const PHINode *otherPHI = cast<PHINode>(I);
-    return std::equal(thisPHI->block_begin(), thisPHI->block_end(),
-                      otherPHI->block_begin());
+  if (const PHINode *Phi = dyn_cast<PHINode>(this)) {
+    const PHINode *OtherPhi = cast<PHINode>(I);
+    return equal(Phi->blocks(), OtherPhi->blocks());
   }
 
   return this->hasSameSpecialState(I, /*IgnoreAlignment=*/false,