From: Joey Gouly <joey.gouly@gmail.com>
Date: Tue, 7 Feb 2017 11:58:22 +0000 (+0000)
Subject: [APInt] Fix rotl/rotr when the shift amount is greater than the total bit width.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f83a9ee2dfc4808fdbf4dcd4555e2fb3776cedee;p=llvm

[APInt] Fix rotl/rotr when the shift amount is greater than the total bit width.

Review: https://reviews.llvm.org/D27749


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294295 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Support/APInt.cpp b/lib/Support/APInt.cpp
index 7b3be916f31..7e17e42dc91 100644
--- a/lib/Support/APInt.cpp
+++ b/lib/Support/APInt.cpp
@@ -1252,8 +1252,21 @@ APInt APInt::shlSlowCase(unsigned shiftAmt) const {
   return Result;
 }
 
+// Calculate the rotate amount modulo the bit width.
+static unsigned rotateModulo(unsigned BitWidth, const APInt &rotateAmt) {
+  unsigned rotBitWidth = rotateAmt.getBitWidth();
+  APInt rot = rotateAmt;
+  if (rotBitWidth < BitWidth) {
+    // Extend the rotate APInt, so that the urem doesn't divide by 0.
+    // e.g. APInt(1, 32) would give APInt(1, 0).
+    rot = rotateAmt.zext(BitWidth);
+  }
+  rot = rot.urem(APInt(rot.getBitWidth(), BitWidth));
+  return rot.getLimitedValue(BitWidth);
+}
+
 APInt APInt::rotl(const APInt &rotateAmt) const {
-  return rotl((unsigned)rotateAmt.getLimitedValue(BitWidth));
+  return rotl(rotateModulo(BitWidth, rotateAmt));
 }
 
 APInt APInt::rotl(unsigned rotateAmt) const {
@@ -1264,7 +1277,7 @@ APInt APInt::rotl(unsigned rotateAmt) const {
 }
 
 APInt APInt::rotr(const APInt &rotateAmt) const {
-  return rotr((unsigned)rotateAmt.getLimitedValue(BitWidth));
+  return rotr(rotateModulo(BitWidth, rotateAmt));
 }
 
 APInt APInt::rotr(unsigned rotateAmt) const {
diff --git a/unittests/ADT/APIntTest.cpp b/unittests/ADT/APIntTest.cpp
index 130bc256b2c..c939c3942d7 100644
--- a/unittests/ADT/APIntTest.cpp
+++ b/unittests/ADT/APIntTest.cpp
@@ -1060,6 +1060,29 @@ TEST(APIntTest, Rotate) {
   EXPECT_EQ(APInt(8, 1),  APInt(8, 16).rotl(4));
   EXPECT_EQ(APInt(8, 16), APInt(8, 16).rotl(8));
 
+  EXPECT_EQ(APInt(32, 2), APInt(32, 1).rotl(33));
+  EXPECT_EQ(APInt(32, 2), APInt(32, 1).rotl(APInt(32, 33)));
+
+  EXPECT_EQ(APInt(32, 2), APInt(32, 1).rotl(33));
+  EXPECT_EQ(APInt(32, 2), APInt(32, 1).rotl(APInt(32, 33)));
+  EXPECT_EQ(APInt(32, 2), APInt(32, 1).rotl(APInt(33, 33)));
+  EXPECT_EQ(APInt(32, (1 << 8)), APInt(32, 1).rotl(APInt(32, 40)));
+  EXPECT_EQ(APInt(32, (1 << 30)), APInt(32, 1).rotl(APInt(31, 30)));
+  EXPECT_EQ(APInt(32, (1 << 31)), APInt(32, 1).rotl(APInt(31, 31)));
+
+  EXPECT_EQ(APInt(32, 1), APInt(32, 1).rotl(APInt(1, 0)));
+  EXPECT_EQ(APInt(32, 2), APInt(32, 1).rotl(APInt(1, 1)));
+
+  EXPECT_EQ(APInt(32, 16), APInt(32, 1).rotl(APInt(3, 4)));
+
+  EXPECT_EQ(APInt(32, 1), APInt(32, 1).rotl(APInt(64, 64)));
+  EXPECT_EQ(APInt(32, 2), APInt(32, 1).rotl(APInt(64, 65)));
+
+  EXPECT_EQ(APInt(7, 24), APInt(7, 3).rotl(APInt(7, 3)));
+  EXPECT_EQ(APInt(7, 24), APInt(7, 3).rotl(APInt(7, 10)));
+  EXPECT_EQ(APInt(7, 24), APInt(7, 3).rotl(APInt(5, 10)));
+  EXPECT_EQ(APInt(7, 6), APInt(7, 3).rotl(APInt(12, 120)));
+
   EXPECT_EQ(APInt(8, 16), APInt(8, 16).rotr(0));
   EXPECT_EQ(APInt(8, 8),  APInt(8, 16).rotr(1));
   EXPECT_EQ(APInt(8, 4),  APInt(8, 16).rotr(2));
@@ -1072,9 +1095,36 @@ TEST(APIntTest, Rotate) {
   EXPECT_EQ(APInt(8, 16),  APInt(8, 1).rotr(4));
   EXPECT_EQ(APInt(8, 1),   APInt(8, 1).rotr(8));
 
-  APInt Big(256, "00004000800000000000000000003fff8000000000000000", 16);
-  APInt Rot(256, "3fff80000000000000000000000000000000000040008000", 16);
+  EXPECT_EQ(APInt(32, (1 << 31)), APInt(32, 1).rotr(33));
+  EXPECT_EQ(APInt(32, (1 << 31)), APInt(32, 1).rotr(APInt(32, 33)));
+
+  EXPECT_EQ(APInt(32, (1 << 31)), APInt(32, 1).rotr(33));
+  EXPECT_EQ(APInt(32, (1 << 31)), APInt(32, 1).rotr(APInt(32, 33)));
+  EXPECT_EQ(APInt(32, (1 << 31)), APInt(32, 1).rotr(APInt(33, 33)));
+  EXPECT_EQ(APInt(32, (1 << 24)), APInt(32, 1).rotr(APInt(32, 40)));
+
+  EXPECT_EQ(APInt(32, (1 << 2)), APInt(32, 1).rotr(APInt(31, 30)));
+  EXPECT_EQ(APInt(32, (1 << 1)), APInt(32, 1).rotr(APInt(31, 31)));
+
+  EXPECT_EQ(APInt(32, 1), APInt(32, 1).rotr(APInt(1, 0)));
+  EXPECT_EQ(APInt(32, (1 << 31)), APInt(32, 1).rotr(APInt(1, 1)));
+
+  EXPECT_EQ(APInt(32, (1 << 28)), APInt(32, 1).rotr(APInt(3, 4)));
+
+  EXPECT_EQ(APInt(32, 1), APInt(32, 1).rotr(APInt(64, 64)));
+  EXPECT_EQ(APInt(32, (1 << 31)), APInt(32, 1).rotr(APInt(64, 65)));
+
+  EXPECT_EQ(APInt(7, 48), APInt(7, 3).rotr(APInt(7, 3)));
+  EXPECT_EQ(APInt(7, 48), APInt(7, 3).rotr(APInt(7, 10)));
+  EXPECT_EQ(APInt(7, 48), APInt(7, 3).rotr(APInt(5, 10)));
+  EXPECT_EQ(APInt(7, 65), APInt(7, 3).rotr(APInt(12, 120)));
+
+  APInt Big(256, "00004000800000000000000000003fff8000000000000003", 16);
+  APInt Rot(256, "3fff80000000000000030000000000000000000040008000", 16);
   EXPECT_EQ(Rot, Big.rotr(144));
+
+  EXPECT_EQ(APInt(32, 8), APInt(32, 1).rotl(Big));
+  EXPECT_EQ(APInt(32, (1 << 29)), APInt(32, 1).rotr(Big));
 }
 
 TEST(APIntTest, Splat) {