[PATCH] D43363: [APInt] Fix extractBits to correctly handle Result.isSingleWord() case.

[Tim Shen via Phabricator via llvm-commits]

timshen created this revision.
timshen added a reviewer: RKSimon.
Herald added subscribers: hiraditya, sanjoy.

extractBits assumes that `!this->isSingleWord() implies !Result.isSingleWord()`, which may not necessarily be true. Handle both cases.


https://reviews.llvm.org/D43363

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


Index: llvm/unittests/ADT/APIntTest.cpp
===================================================================
--- llvm/unittests/ADT/APIntTest.cpp
+++ llvm/unittests/ADT/APIntTest.cpp
@@ -1768,6 +1768,13 @@
             i257.extractBits(128, 1).getSExtValue());
   EXPECT_EQ(static_cast<int64_t>(0xFFFFFFFFFF80007Full),
             i257.extractBits(129, 1).getSExtValue());
+
+  EXPECT_EQ(APInt(48, 0),
+            APInt(144, "281474976710655", 10).extractBits(48, 48));
+  EXPECT_EQ(APInt(48, 0x0000ffffffffffffull),
+            APInt(144, "281474976710655", 10).extractBits(48, 0));
+  EXPECT_EQ(APInt(48, 0x00007fffffffffffull),
+            APInt(144, "281474976710655", 10).extractBits(48, 1));
 }
 
 TEST(APIntTest, getLowBitsSet) {
Index: llvm/lib/Support/APInt.cpp
===================================================================
--- llvm/lib/Support/APInt.cpp
+++ llvm/lib/Support/APInt.cpp
@@ -428,11 +428,12 @@
   unsigned NumSrcWords = getNumWords();
   unsigned NumDstWords = Result.getNumWords();
 
+  uint64_t *DestPtr = Result.isSingleWord() ? &Result.U.VAL : Result.U.pVal;
   for (unsigned word = 0; word < NumDstWords; ++word) {
     uint64_t w0 = U.pVal[loWord + word];
     uint64_t w1 =
         (loWord + word + 1) < NumSrcWords ? U.pVal[loWord + word + 1] : 0;
-    Result.U.pVal[word] = (w0 >> loBit) | (w1 << (APINT_BITS_PER_WORD - loBit));
+    DestPtr[word] = (w0 >> loBit) | (w1 << (APINT_BITS_PER_WORD - loBit));
   }
 
   return Result.clearUnusedBits();


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