[APInt] Add ashrInPlace method and implement ashr using it. Also fix a bug in the shift by BitWidth handling.

For single word, shift by BitWidth was always returning 0, but for multiword it was based on original sign. Now single word matches multi word.

llvm-svn: 301094

1 files changed, 19 insertions, 1 deletions

diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index 5d3afe9a159..6b889bf2dfd 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -288,7 +288,7 @@ TEST(APIntTest, i1) {
   EXPECT_EQ(zero, one.shl(1));
   EXPECT_EQ(one, one.shl(0));
   EXPECT_EQ(zero, one.lshr(1));
-  EXPECT_EQ(zero, one.ashr(1));
+  EXPECT_EQ(one, one.ashr(1));
 
   // Rotates.
   EXPECT_EQ(one, one.rotl(0));
@@ -2024,6 +2024,24 @@ TEST(APIntTest, LogicalRightShift) {
   EXPECT_EQ(0, neg_one.lshr(128));
 }
 
+TEST(APIntTest, ArithmeticRightShift) {
+  // Ensure we handle large shifts of multi-word.
+  const APInt signmin32(APInt::getSignedMinValue(32));
+  EXPECT_TRUE(signmin32.ashr(32).isAllOnesValue());
+
+  // Ensure we handle large shifts of multi-word.
+  const APInt umax32(APInt::getSignedMaxValue(32));
+  EXPECT_EQ(0, umax32.ashr(32));
+
+  // Ensure we handle large shifts of multi-word.
+  const APInt signmin128(APInt::getSignedMinValue(128));
+  EXPECT_TRUE(signmin128.ashr(128).isAllOnesValue());
+
+  // Ensure we handle large shifts of multi-word.
+  const APInt umax128(APInt::getSignedMaxValue(128));
+  EXPECT_EQ(0, umax128.ashr(128));
+}
+
 TEST(APIntTest, LeftShift) {
   APInt i256(APInt::getLowBitsSet(256, 2));