[ELF] Use SmallVector for MergeInputSection::pieces. NFC
sizeof(pieces) decreases from 24 to 16 on ELF64.
One BumpPtrAllocator can store more MergeInputSections.
The lld executable becomes smaller.
diff --git a/lld/ELF/InputSection.h b/lld/ELF/InputSection.h
index 7ddc439..70bbe49 100644
--- a/lld/ELF/InputSection.h
+++ b/lld/ELF/InputSection.h
@@ -278,7 +278,7 @@
// Splittable sections are handled as a sequence of data
// rather than a single large blob of data.
- std::vector<SectionPiece> pieces;
+ SmallVector<SectionPiece, 0> pieces;
// Returns I'th piece's data. This function is very hot when
// string merging is enabled, so we want to inline.
