COFF: De-virtualize and inline garbage collector functions.
isRoot, isLive and markLive functions are called very frequently.
Previously, they were virtual functions. This patch make them
non-virtual.
Also this patch checks chunk liveness before calling its mark().
Previously, we did that at beginning of markLive(), so the virtual
function would return immediately if it's live. That was inefficient.
llvm-svn: 239458
diff --git a/lld/COFF/Chunks.cpp b/lld/COFF/Chunks.cpp
index cce6846..c8b2262 100644
--- a/lld/COFF/Chunks.cpp
+++ b/lld/COFF/Chunks.cpp
@@ -30,9 +30,21 @@
: File(F), Header(H), SectionIndex(SI) {
// Initialize SectionName.
File->getCOFFObj()->getSectionName(Header, SectionName);
+
// Bit [20:24] contains section alignment.
unsigned Shift = ((Header->Characteristics & 0xF00000) >> 20) - 1;
Align = uint32_t(1) << Shift;
+
+ // When a new chunk is created, we don't if if it's going to make it
+ // to the final output. Initially all sections are unmarked in terms
+ // of garbage collection. The writer will call markLive() to mark
+ // all reachable section chunks.
+ Live = false;
+
+ // COMDAT sections are not GC root. Non-text sections are not
+ // subject of garbage collection (thus they are root).
+ if (!isCOMDAT() && !(Header->Characteristics & IMAGE_SCN_CNT_CODE))
+ Root = true;
}
void SectionChunk::writeTo(uint8_t *Buf) {
@@ -50,22 +62,7 @@
}
}
-// Returns true if this chunk should be considered as a GC root.
-bool SectionChunk::isRoot() {
- // COMDAT sections are live only when they are referenced by something else.
- if (isCOMDAT())
- return false;
-
- // Associative sections are live if their parent COMDATs are live,
- // and vice versa, so they are not considered live by themselves.
- if (IsAssocChild)
- return false;
-
- // Only code is subject of dead-stripping.
- return !(Header->Characteristics & IMAGE_SCN_CNT_CODE);
-}
-
-void SectionChunk::markLive() {
+void SectionChunk::mark() {
if (Live)
return;
Live = true;
@@ -84,8 +81,10 @@
}
void SectionChunk::addAssociative(SectionChunk *Child) {
- Child->IsAssocChild = true;
AssocChildren.push_back(Child);
+ // Associative sections are live if their parent COMDATs are live,
+ // and vice versa, so they are not considered live by themselves.
+ Child->Root = false;
}
static void add16(uint8_t *P, int16_t V) { write16le(P, read16le(P) + V); }