[llvm] ad3e0e4 - [APInt] Add APInt::isOneBitSet helper.

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2023-01-03T16:10:29Z
New Revision: ad3e0e4b419461bbc56a79a33167e93141ba5859

URL: https://github.com/llvm/llvm-project/commit/ad3e0e4b419461bbc56a79a33167e93141ba5859
DIFF: https://github.com/llvm/llvm-project/commit/ad3e0e4b419461bbc56a79a33167e93141ba5859.diff

LOG: [APInt] Add APInt::isOneBitSet helper.

Equivalent tester for the APInt::getOneBitSet builder.

This should allow us to remove a number of cases where we're doing "Val == (1 << BitNo)" style code patterns.

Added: 
    

Modified: 
    llvm/include/llvm/ADT/APInt.h
    llvm/unittests/ADT/APIntTest.cpp

Removed: 
    


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diff  --git a/llvm/include/llvm/ADT/APInt.h b/llvm/include/llvm/ADT/APInt.h
index ab8bf3eb1fe1..4b0886835824 100644
--- a/llvm/include/llvm/ADT/APInt.h
+++ b/llvm/include/llvm/ADT/APInt.h
@@ -343,6 +343,13 @@ class [[nodiscard]] APInt {
   /// \returns true if this APInt is non-positive.
   bool isNonPositive() const { return !isStrictlyPositive(); }
 
+  /// Determine if this APInt Value only has the specified bit set.
+  ///
+  /// \returns true if this APInt only has the specified bit set.
+  bool isOneBitSet(unsigned BitNo) const {
+    return (*this)[BitNo] && countPopulation() == 1;
+  }
+
   /// Determine if all bits are set.  This is true for zero-width values.
   bool isAllOnes() const {
     if (BitWidth == 0)

diff  --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index e7632c088a9c..0377e05c11cd 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -1793,6 +1793,16 @@ TEST(APIntTest, isShiftedMask) {
   }
 }
 
+TEST(APIntTest, isOneBitSet) {
+  EXPECT_FALSE(APInt(5, 0x00).isOneBitSet(0));
+  EXPECT_FALSE(APInt(5, 0x02).isOneBitSet(0));
+  EXPECT_FALSE(APInt(5, 0x03).isOneBitSet(0));
+  EXPECT_TRUE(APInt(5, 0x02).isOneBitSet(1));
+  EXPECT_TRUE(APInt(32, (unsigned)(0xffu << 31)).isOneBitSet(31));
+
+  EXPECT_TRUE(APInt::getOneBitSet(255, 13).isOneBitSet(13));
+}
+
 TEST(APIntTest, isPowerOf2) {
   EXPECT_FALSE(APInt(5, 0x00).isPowerOf2());
   EXPECT_FALSE(APInt(32, 0x11).isPowerOf2());