[PATCH] D27749: [APFloat] Fix rotl/rotr when the shift amount is greater than the total bit width.

[Joey Gouly via Phabricator via llvm-commits]

joey updated this revision to Diff 83216.
joey added a comment.

Updated the code to use 'urem' to get the remainder, rather than calling getZExtValue.

Should the APInt rotateAmt need to have the same bitwidth as the APInt the rotl is being called on? urem and a few other methods need that.


Repository:
  rL LLVM

https://reviews.llvm.org/D27749

Files:
  lib/Support/APInt.cpp
  unittests/ADT/APIntTest.cpp


Index: unittests/ADT/APIntTest.cpp
===================================================================
--- unittests/ADT/APIntTest.cpp
+++ unittests/ADT/APIntTest.cpp
@@ -978,6 +978,9 @@
   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(33, 33)));
+
   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));
@@ -990,6 +993,9 @@
   EXPECT_EQ(APInt(8, 16),  APInt(8, 1).rotr(4));
   EXPECT_EQ(APInt(8, 1),   APInt(8, 1).rotr(8));
 
+  EXPECT_EQ(APInt(32, (1 << 31)), APInt(32, 1).rotr(33));
+  EXPECT_EQ(APInt(32, (1 << 31)), APInt(32, 1).rotr(APInt(32, 33)));
+
   APInt Big(256, "00004000800000000000000000003fff8000000000000000", 16);
   APInt Rot(256, "3fff80000000000000000000000000000000000040008000", 16);
   EXPECT_EQ(Rot, Big.rotr(144));
Index: lib/Support/APInt.cpp
===================================================================
--- lib/Support/APInt.cpp
+++ lib/Support/APInt.cpp
@@ -1245,7 +1245,9 @@
 }
 
 APInt APInt::rotl(const APInt &rotateAmt) const {
-  return rotl((unsigned)rotateAmt.getLimitedValue(BitWidth));
+  unsigned rotBitWidth = rotateAmt.getBitWidth();
+  APInt rem(rotateAmt.urem(APInt(rotBitWidth, BitWidth)));
+  return rotl((unsigned)rem.getLimitedValue(BitWidth));
 }
 
 APInt APInt::rotl(unsigned rotateAmt) const {
@@ -1256,7 +1258,9 @@
 }
 
 APInt APInt::rotr(const APInt &rotateAmt) const {
-  return rotr((unsigned)rotateAmt.getLimitedValue(BitWidth));
+  unsigned rotBitWidth = rotateAmt.getBitWidth();
+  APInt rem(rotateAmt.urem(APInt(rotBitWidth, BitWidth)));
+  return rotr((unsigned)rem.getLimitedValue(BitWidth));
 }
 
 APInt APInt::rotr(unsigned rotateAmt) const {


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