WordPos should be less than BITWORDS_PER_ELEMENT

[SwayamInSync]

Bits is declared as:

BitWord Bits[BITWORDS_PER_ELEMENT];

The change modifies an assert condition to ensure that WordPos is strictly less than BITWORDS_PER_ELEMENT rather than less than or equal to it.

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[llvmbot]

@llvm/pr-subscribers-llvm-adt

Author: Swayam (SwayamInSync)

Changes

Bits is declared as:

BitWord Bits[BITWORDS_PER_ELEMENT];

The change modifies an assert condition to ensure that WordPos is strictly less than BITWORDS_PER_ELEMENT rather than less than or equal to it.

---

Full diff: https://github.com/llvm/llvm-project/pull/142959.diff

1 Files Affected:

• (modified) llvm/include/llvm/ADT/SparseBitVector.h (+1-1)

diff --git a/llvm/include/llvm/ADT/SparseBitVector.h b/llvm/include/llvm/ADT/SparseBitVector.h
index 7151af6146e6e..3fec695c6e461 100644
--- a/llvm/include/llvm/ADT/SparseBitVector.h
+++ b/llvm/include/llvm/ADT/SparseBitVector.h
@@ -152,7 +152,7 @@ template <unsigned ElementSize = 128> struct SparseBitVectorElement {
     unsigned WordPos = Curr / BITWORD_SIZE;
     unsigned BitPos = Curr % BITWORD_SIZE;
     BitWord Copy = Bits[WordPos];
-    assert(WordPos <= BITWORDS_PER_ELEMENT
+    assert(WordPos < BITWORDS_PER_ELEMENT
            && "Word Position outside of element");
 
     // Mask off previous bits.

[kuhar]

Do we have any tests that exercises this?

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⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff HEAD~1 HEAD --extensions h -- llvm/include/llvm/ADT/SparseBitVector.h

View the diff from clang-format here.

diff --git a/llvm/include/llvm/ADT/SparseBitVector.h b/llvm/include/llvm/ADT/SparseBitVector.h
index 3fec695c6..b353fe406 100644
--- a/llvm/include/llvm/ADT/SparseBitVector.h
+++ b/llvm/include/llvm/ADT/SparseBitVector.h
@@ -152,8 +152,8 @@ public:
     unsigned WordPos = Curr / BITWORD_SIZE;
     unsigned BitPos = Curr % BITWORD_SIZE;
     BitWord Copy = Bits[WordPos];
-    assert(WordPos < BITWORDS_PER_ELEMENT
-           && "Word Position outside of element");
+    assert(WordPos < BITWORDS_PER_ELEMENT &&
+           "Word Position outside of element");
 
     // Mask off previous bits.
     Copy &= ~0UL << BitPos;

[SwayamInSync]

I didn't find any specific tests for this but building clang warns about this and the assertion statement is covering it illegally as per the declaration

[kuhar]

Actually, the surrounding code is weird. Doesn't this use variable length arrays since WordPos depends on the function argument?