[clang] [SCCP] [Transform] Adding ICMP folding for zext and sext in SCCPSolver (PR #67594)

[Marianne Mailhot-Sarrasin via cfe-commits]

================
@@ -193,6 +193,60 @@ static bool replaceSignedInst(SCCPSolver &Solver,
     NewInst = BinaryOperator::Create(NewOpcode, Op0, Op1, "", &Inst);
     break;
   }
+  case Instruction::ICmp: {
+    ICmpInst &ICmp = cast<ICmpInst>(Inst);
+  
+    ZExtInst *Op0_zext = dyn_cast<ZExtInst>(ICmp.getOperand(0));
+    SExtInst *Op0_sext = dyn_cast<SExtInst>(ICmp.getOperand(0));
+  
+    ZExtInst *Op1_zext = dyn_cast<ZExtInst>(ICmp.getOperand(1));
+    SExtInst *Op1_sext = dyn_cast<SExtInst>(ICmp.getOperand(1));
+  
+    CastInst *Op0;
+    CastInst *Op1;
+  
+    if (Op0_zext) Op0 = Op0_zext; else Op0 = Op0_sext;
+    if (Op1_zext) Op1 = Op1_zext; else Op1 = Op1_sext;
+  
+    bool reversed = false;
+  
+    if (!Op0 || !Op1){
+      // Op0 and Op1 must be defined
+      return false;
+    } 
+  
+    if (Op1_zext && (! Op0_zext)){
+      // We force Op0 to be a zext and reverse the arguments
+      //   at the end if we swap
+      reversed = true; 
+  
+      std::swap(Op0_zext, Op1_zext);
+      std::swap(Op0_sext, Op1_sext);
+      std::swap(Op0, Op1);
+    }
+  
+  
+    if(Op0->getType() != Op1->getType()){
----------------
mariannems wrote:

Its is always better to exit early. This check should ideally be done before potential swapping.

https://github.com/llvm/llvm-project/pull/67594