[llvm] [ConstantRange] Fix off by 1 bugs in UIToFP and SIToFP handling. (PR #86041)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/86041

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.

CC: @AtariDreams 

>From 3054d11dc1f6edd7f4227c4a7999a017bc0a9280 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Wed, 20 Mar 2024 16:36:44 -0700
Subject: [PATCH] [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.
---
 llvm/lib/IR/ConstantRange.cpp           |  4 ++--
 llvm/unittests/IR/ConstantRangeTest.cpp | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index 3394a1ec8dc476..59e7a9f5eb1114 100644
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/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:
diff --git a/llvm/unittests/IR/ConstantRangeTest.cpp b/llvm/unittests/IR/ConstantRangeTest.cpp
index 34a162a5514e95..8ec120d70e99f6 100644
--- a/llvm/unittests/IR/ConstantRangeTest.cpp
+++ b/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) {