[PATCH] D27241: Bitcode: Correctly handle Fixed and VBR arrays in BitstreamCursor::skipRecord().

[Peter Collingbourne via Phabricator via llvm-commits]

pcc created this revision.
pcc added a reviewer: mehdi_amini.
pcc added a subscriber: llvm-commits.

The assertions were wrong; we need to call getEncodingData() on the element,
not the array. While here, simplify the skipRecord() implementation for Fixed
and Char6 arrays. This is tested by the code I added to llvm-bcanalyzer
which makes sure that we can skip any record.


https://reviews.llvm.org/D27241

Files:
  llvm/lib/Bitcode/Reader/BitstreamReader.cpp
  llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp


Index: llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
===================================================================
--- llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
+++ llvm/tools/llvm-bcanalyzer/llvm-bcanalyzer.cpp
@@ -567,7 +567,7 @@
     ++BlockStats.NumRecords;
 
     StringRef Blob;
-    unsigned CurrentRecordPos = Stream.getCurrentByteNo();
+    unsigned CurrentRecordPos = Stream.GetCurrentBitNo();
     unsigned Code = Stream.readRecord(Entry.ID, Record, &Blob);
 
     // Increment the # occurrences of this code.
@@ -608,7 +608,7 @@
           SHA1 Hasher;
           StringRef Hash;
           {
-            int BlockSize = CurrentRecordPos - BlockEntryPos;
+            int BlockSize = (CurrentRecordPos / 8) - BlockEntryPos;
             auto Ptr = Stream.getPointerToByte(BlockEntryPos, BlockSize);
             Hasher.update(ArrayRef<uint8_t>(Ptr, BlockSize));
             Hash = Hasher.result();
@@ -675,6 +675,10 @@
 
       outs() << "\n";
     }
+
+    // Make sure that we can skip the current record.
+    Stream.JumpToBit(CurrentRecordPos);
+    Stream.skipRecord(Entry.ID);
   }
 }
 
Index: llvm/lib/Bitcode/Reader/BitstreamReader.cpp
===================================================================
--- llvm/lib/Bitcode/Reader/BitstreamReader.cpp
+++ llvm/lib/Bitcode/Reader/BitstreamReader.cpp
@@ -131,18 +131,16 @@
       default:
         report_fatal_error("Array element type can't be an Array or a Blob");
       case BitCodeAbbrevOp::Fixed:
-        assert((unsigned)Op.getEncodingData() <= MaxChunkSize);
-        for (; NumElts; --NumElts)
-          Read((unsigned)EltEnc.getEncodingData());
+        assert((unsigned)EltEnc.getEncodingData() <= MaxChunkSize);
+        JumpToBit(GetCurrentBitNo() + NumElts * EltEnc.getEncodingData());
         break;
       case BitCodeAbbrevOp::VBR:
-        assert((unsigned)Op.getEncodingData() <= MaxChunkSize);
+        assert((unsigned)EltEnc.getEncodingData() <= MaxChunkSize);
         for (; NumElts; --NumElts)
           ReadVBR64((unsigned)EltEnc.getEncodingData());
         break;
       case BitCodeAbbrevOp::Char6:
-        for (; NumElts; --NumElts)
-          Read(6);
+        JumpToBit(GetCurrentBitNo() + NumElts * 6);
         break;
       }
       continue;


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