[ConstantRange] Fix off by 1 bugs in UIToFP and SIToFP handling.

We were passing the min and max values of the range to the ConstantRange constructor, but the constructor expects the upper bound to 1 more than the max value so we need to add 1. We also need to use getNonEmpty so that passing 0, 0 to the constructor creates a full range rather than an empty range. And passing smin, smax+1 doesn't cause an assertion. I believe this fixes at least some of the reason #79158 was reverted.

Author: topperc

llvm/lib/IR/ConstantRange.cpp

@@ -746,7 +746,7 @@ ConstantRange ConstantRange::castOp(Instruction::CastOps CastOp,
  Min = Min.zext(ResultBitWidth);
  Max = Max.zext(ResultBitWidth);
  }
- return ConstantRange(std::move(Min), std::move(Max));
+ return getNonEmpty(std::move(Min), std::move(Max) + 1);
  }
  case Instruction::SIToFP: {
  // TODO: use input range if available
@@ -757,7 +757,7 @@ ConstantRange ConstantRange::castOp(Instruction::CastOps CastOp,
  SMin = SMin.sext(ResultBitWidth);
  SMax = SMax.sext(ResultBitWidth);
  }
- return ConstantRange(std::move(SMin), std::move(SMax));
+ return getNonEmpty(std::move(SMin), std::move(SMax) + 1);
  }
  case Instruction::FPTrunc:
  case Instruction::FPExt:

llvm/test/Transforms/Float2Int/pr79158.ll

@@ -6,8 +6,9 @@ define i32 @pr79158(i32 %x.i.0.x.i.0.x.0.x.0.x.0..i) {
 ; CHECK-SAME: i32 [[X_I_0_X_I_0_X_0_X_0_X_0__I:%.*]]) {
 ; CHECK-NEXT: entry:
 ; CHECK-NEXT: [[CMP_I:%.*]] = icmp sgt i32 [[X_I_0_X_I_0_X_0_X_0_X_0__I]], 0
-; CHECK-NEXT: [[TMP0:%.*]] = zext i1 [[CMP_I]] to i32
-; CHECK-NEXT: [[MUL_I1:%.*]] = mul i32 [[TMP0]], 2147483647
+; CHECK-NEXT: [[TMP0:%.*]] = zext i1 [[CMP_I]] to i64
+; CHECK-NEXT: [[MUL_I2:%.*]] = mul i64 [[TMP0]], 4294967295
+; CHECK-NEXT: [[MUL_I1:%.*]] = trunc i64 [[MUL_I2]] to i32
 ; CHECK-NEXT: ret i32 [[MUL_I1]]
 ;
 entry:

llvm/unittests/IR/ConstantRangeTest.cpp

@@ -2479,6 +2479,24 @@ TEST_F(ConstantRangeTest, castOps) {
  ConstantRange IntToPtr = A.castOp(Instruction::IntToPtr, 64);
  EXPECT_EQ(64u, IntToPtr.getBitWidth());
  EXPECT_TRUE(IntToPtr.isFullSet());
+
+ ConstantRange UIToFP = A.castOp(Instruction::UIToFP, 16);
+ EXPECT_EQ(16u, UIToFP.getBitWidth());
+ EXPECT_TRUE(UIToFP.isFullSet());
+
+ ConstantRange UIToFP2 = A.castOp(Instruction::UIToFP, 64);
+ ConstantRange B(APInt(64, 0), APInt(64, 65536));
+ EXPECT_EQ(64u, UIToFP2.getBitWidth());
+ EXPECT_EQ(B, UIToFP2);
+
+ ConstantRange SIToFP = A.castOp(Instruction::SIToFP, 16);
+ EXPECT_EQ(16u, SIToFP.getBitWidth());
+ EXPECT_TRUE(SIToFP.isFullSet());
+
+ ConstantRange SIToFP2 = A.castOp(Instruction::SIToFP, 64);
+ ConstantRange C(APInt(64, -32768), APInt(64, 32768));
+ EXPECT_EQ(64u, SIToFP2.getBitWidth());
+ EXPECT_EQ(C, SIToFP2);
 }
 
 TEST_F(ConstantRangeTest, binaryAnd) {