Transform/Float2Int: Don't rely on hack support for floating point type in ConstantRange

[jvesely]

Summary

Don't rely on ConstantRange treating float operations using integer ranges.
Opencode custom FPto{SI,UI} operations.

Floating point support for ConstantRange is added in D78220

llvm/lib/Transforms/Scalar/Float2Int.cpp

while (!Worklist.empty()) {
 
     switch (I->getOpcode()) {
       // FIXME: Handle select and phi nodes.
     default:
       // Path terminated uncleanly.
       seen(I, badRange());
       break;
 
-    case Instruction::UIToFP:
+    case Instruction::UIToFP: {
+      // Path terminated cleanly - use the type of the integer input to seed
+      // the analysis.
+      unsigned BW = I->getOperand(0)->getType()->getPrimitiveSizeInBits();
+      APInt Min = APInt::getMinValue(BW).zextOrSelf(MaxIntegerBW + 1);
+      APInt Max = APInt::getMaxValue(BW).zextOrSelf(MaxIntegerBW + 1);
+      seen(I, validateRange(ConstantRange(std::move(Min), std::move(Max))));
+      continue;
+    }
     case Instruction::SIToFP: {
       // Path terminated cleanly - use the type of the integer input to seed
       // the analysis.
       unsigned BW = I->getOperand(0)->getType()->getPrimitiveSizeInBits();
-      auto Input = ConstantRange::getFull(BW);
-      auto CastOp = (Instruction::CastOps)I->getOpcode();
-      seen(I, validateRange(Input.castOp(CastOp, MaxIntegerBW+1)));
+      APInt Min = APInt::getSignedMinValue(BW).sextOrSelf(MaxIntegerBW + 1);
+      APInt Max = APInt::getSignedMaxValue(BW).sextOrSelf(MaxIntegerBW + 1);
+      seen(I, validateRange(ConstantRange(std::move(Min), std::move(Max))));
       continue;
     }
 
     case Instruction::FNeg:
     case Instruction::FAdd:
     case Instruction::FSub:
     case Instruction::FMul:
     case Instruction::FPToUI:
case Instruction::FNeg:
       };
       break;
 
     case Instruction::FAdd:
     case Instruction::FSub:
     case Instruction::FMul:
       Op = [I](ArrayRef<ConstantRange> Ops) {
         assert(Ops.size() == 2 && "its a binary operator!");
-        auto BinOp = (Instruction::BinaryOps) I->getOpcode();
+        auto BinOp = mapBinOpcode(I->getOpcode());
         return Ops[0].binaryOp(BinOp, Ops[1]);
       };
       break;
 
     //
     // Root-only instructions - we'll only see these if they're the
     //                          first node in a walk.
     //
     case Instruction::FPToUI:
     case Instruction::FPToSI:
-      Op = [I](ArrayRef<ConstantRange> Ops) {
+      Op = [I, this](ArrayRef<ConstantRange> Ops) {
         assert(Ops.size() == 1 && "FPTo[US]I is a unary operator!");
         // Note: We're ignoring the casts output size here as that's what the
         // caller expects.
-        auto CastOp = (Instruction::CastOps)I->getOpcode();
-        return Ops[0].castOp(CastOp, MaxIntegerBW+1);
+  if (Ops[0].getBitWidth() == MaxIntegerBW+1)
+          return Ops[0];
+        return badRange();
       };
       break;
 
     case Instruction::FCmp:
       Op = [](ArrayRef<ConstantRange> Ops) {
         assert(Ops.size() == 2 && "FCmp is a binary operator!");
         return Ops[0].unionWith(Ops[1]);
       };