[APInt] Merge the multiword code from lshrInPlace and tcShiftRight into a single implementation

This merges the two different multiword shift right implementations into a single version located in tcShiftRight. lshrInPlace now calls tcShiftRight for the multiword case.

I retained the memmove fast path from lshrInPlace and used a memset for the zeroing. The for loop is basically tcShiftRight's implementation with the zeroing and the intra-shift of 0 removed.

Differential Revision: https://reviews.llvm.org/D32114

llvm-svn: 300503

1 files changed, 33 insertions, 5 deletions

diff --git a/llvm/unittests/ADT/APIntTest.cpp b/llvm/unittests/ADT/APIntTest.cpp
index d24d5800a40..0bd309dd087 100644
--- a/llvm/unittests/ADT/APIntTest.cpp
+++ b/llvm/unittests/ADT/APIntTest.cpp
@@ -37,11 +37,6 @@ TEST(APIntTest, i64_ArithmeticRightShiftNegative) {
   EXPECT_EQ(neg_one, neg_one.ashr(7));
 }
 
-TEST(APIntTest, i64_LogicalRightShiftNegative) {
-  const APInt neg_one(128, static_cast<uint64_t>(-1), true);
-  EXPECT_EQ(0, neg_one.lshr(257));
-}
-
 TEST(APIntTest, i128_NegativeCount) {
   APInt Minus3(128, static_cast<uint64_t>(-3), true);
   EXPECT_EQ(126u, Minus3.countLeadingOnes());
@@ -1996,4 +1991,37 @@ TEST(APIntTest, GCD) {
   EXPECT_EQ(C, HugePrime);
 }
 
+TEST(APIntTest, LogicalRightShift) {
+  APInt i256(APInt::getHighBitsSet(256, 2));
+
+  i256.lshrInPlace(1);
+  EXPECT_EQ(1U, i256.countLeadingZeros());
+  EXPECT_EQ(253U, i256.countTrailingZeros());
+  EXPECT_EQ(2U, i256.countPopulation());
+
+  i256.lshrInPlace(62);
+  EXPECT_EQ(63U, i256.countLeadingZeros());
+  EXPECT_EQ(191U, i256.countTrailingZeros());
+  EXPECT_EQ(2U, i256.countPopulation());
+
+  i256.lshrInPlace(65);
+  EXPECT_EQ(128U, i256.countLeadingZeros());
+  EXPECT_EQ(126U, i256.countTrailingZeros());
+  EXPECT_EQ(2U, i256.countPopulation());
+
+  i256.lshrInPlace(64);
+  EXPECT_EQ(192U, i256.countLeadingZeros());
+  EXPECT_EQ(62U, i256.countTrailingZeros());
+  EXPECT_EQ(2U, i256.countPopulation());
+
+  i256.lshrInPlace(63);
+  EXPECT_EQ(255U, i256.countLeadingZeros());
+  EXPECT_EQ(0U, i256.countTrailingZeros());
+  EXPECT_EQ(1U, i256.countPopulation());
+
+  // Ensure we handle large shifts of multi-word.
+  const APInt neg_one(128, static_cast<uint64_t>(-1), true);
+  EXPECT_EQ(0, neg_one.lshr(257));
+}
+
 } // end anonymous namespace