[APInt] provide a safe API for zext value and sext value.

Currently, APInt::getSExtValue and getZExtValue crashes on values with more than 64 bits.
Users may accidently crash the compiler with this setting when the integer may be i128.
As shown in https://github.com/llvm/llvm-project/issues/59316

In this patch we provide a trySExtValue and tryZExtValue to return an Optional, the user
needs to explictly unwrap it and condsier the possibility where there my no value in it.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D139683

1 files changed, 21 insertions, 0 deletions

diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index 3055581..09c9c8d 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -3134,4 +3134,25 @@ TEST(APIntTest, DenseMap) {
   Map.find(ZeroWidthInt);
 }
 
+TEST(APIntTest, TryExt) {
+  APInt small(32, 42);
+  APInt large(128, {0xffff, 0xffff});
+  ASSERT_TRUE(small.tryZExtValue().has_value());
+  ASSERT_TRUE(small.trySExtValue().has_value());
+  ASSERT_FALSE(large.tryZExtValue().has_value());
+  ASSERT_FALSE(large.trySExtValue().has_value());
+  ASSERT_EQ(small.trySExtValue().value_or(41), 42);
+  ASSERT_EQ(large.trySExtValue().value_or(41), 41);
+
+  APInt negOne32(32, 0);
+  negOne32.setAllBits();
+  ASSERT_EQ(negOne32.trySExtValue().value_or(42), -1);
+  APInt negOne64(64, 0);
+  negOne64.setAllBits();
+  ASSERT_EQ(negOne64.trySExtValue().value_or(42), -1);
+  APInt negOne128(128, 0);
+  negOne128.setAllBits();
+  ASSERT_EQ(negOne128.trySExtValue().value_or(42), 42);
+}
+
 } // end anonymous namespace