Discard the recent work of detecting the optimization pattern to

stop reprocessing, and instead use the current list of 'InsertedInsts'
to keep track of processed instructions.
The work of detecting the pattern needs to detect 4 patterns for
cases when one/both of the parameters are constant.
So the new solution is simpler and more secure.

Author: hassnaaHamdi

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -6405,36 +6405,6 @@ bool CodeGenPrepare::optimizeMulWithOverflow(Instruction *I, bool IsSigned,
   if (!TLI->shouldOptimizeMulOverflowIntrinsic())
     return false;
 
-  // Check if we had already optimized this intrinsic by detecting the pattern of the changes we had made:
-  // Check if we are testing the high bits of the operands:
-  if (BasicBlock *BrBB = I->getParent()->getSinglePredecessor()) {
-    if (BranchInst *Br = dyn_cast<BranchInst>(BrBB->getTerminator()); Br && Br->isConditional()) {
-      if (IsSigned) {
-        // Check: cmp(or(xor(trunc(lshr(x))), xor(trunc(lshr(x)))))
-        if (match(Br->getCondition(),
-                  m_Cmp(m_Or(m_Xor(m_Trunc(m_LShr(m_Specific(I->getOperand(0)), m_Value())), m_Value()),
-                             m_Xor(m_Trunc(m_LShr(m_Specific(I->getOperand(1)), m_Value())), m_Value())),
-                        m_Value()))) {
-          LLVM_DEBUG(dbgs() << "CGP: pattern detected - bail out\n");
-          // Pattern detected, bail out.
-          return false;
-        }
-      }
-      else
-      {
-        // Check: or(cmp(trunc(lshr(x)), cmp(trunc(lshr(y))))
-        if (match(Br->getCondition(),
-                  m_Or(m_Cmp(m_Trunc(m_LShr(m_Specific(I->getOperand(0)), m_Value())), m_Value()),
-                       m_Cmp(m_Trunc(m_LShr(m_Specific(I->getOperand(1)), m_Value())), m_Value())))) {
-          LLVM_DEBUG(dbgs() << "CGP: pattern detected - bail out\n");
-          // Pattern detected, bail out.
-          return false;
-        }
-      }
-
-    }
-  }
-
   if (TLI->getTypeAction(
           I->getContext(),
           TLI->getValueType(*DL, I->getType()->getContainedType(0))) !=
@@ -6459,6 +6429,8 @@ bool CodeGenPrepare::optimizeMulWithOverflow(Instruction *I, bool IsSigned,
   if (!I->getType()->isStructTy() || I->getType()->getStructNumElements() != 2)
     return false;
 
+  // Keep track of the instruction to stop reoptimizing it again.
+  InsertedInsts.insert(I);
   // ----------------------------
 
   // For the simple case where IR just checks the overflow flag, new blocks