ELF: ICF: Include contents of referenced sections in initial partitioning hash. NFCI.
On my machine this reduced median link time of lld-speed-test/chrome
from 2.68s to 2.41s. It also reduces link time of Chrome for Android
with a prototype compiler change that causes the compiler to create
large numbers of identical (modulo relocations) sections from >15
minutes to a few seconds.
Differential Revision: https://reviews.llvm.org/D54773
git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@347594 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/ELF/ICF.cpp b/ELF/ICF.cpp
index 176c627..8446661 100644
--- a/ELF/ICF.cpp
+++ b/ELF/ICF.cpp
@@ -119,6 +119,9 @@
void forEachClass(llvm::function_ref<void(size_t, size_t)> Fn);
+ template <class RelTy>
+ void combineRelocHashes(InputSection *IS, ArrayRef<RelTy> Rels);
+
std::vector<InputSection *> Sections;
// We repeat the main loop while `Repeat` is true.
@@ -423,6 +426,22 @@
++Cnt;
}
+// Combine the hashes of the sections referenced by the given section into its
+// hash.
+template <class ELFT>
+template <class RelTy>
+void ICF<ELFT>::combineRelocHashes(InputSection *IS, ArrayRef<RelTy> Rels) {
+ uint32_t Hash = IS->Class[1];
+ for (RelTy Rel : Rels) {
+ Symbol &S = IS->template getFile<ELFT>()->getRelocTargetSym(Rel);
+ if (auto *D = dyn_cast<Defined>(&S))
+ if (auto *RelSec = dyn_cast_or_null<InputSection>(D->Section))
+ Hash ^= RelSec->Class[1];
+ }
+ // Set MSB to 1 to avoid collisions with non-hash IDs.
+ IS->Class[0] = Hash | (1U << 31);
+}
+
static void print(const Twine &S) {
if (Config->PrintIcfSections)
message(S);
@@ -438,8 +457,14 @@
// Initially, we use hash values to partition sections.
parallelForEach(Sections, [&](InputSection *S) {
- // Set MSB to 1 to avoid collisions with non-hash IDs.
- S->Class[0] = xxHash64(S->data()) | (1U << 31);
+ S->Class[1] = xxHash64(S->data());
+ });
+
+ parallelForEach(Sections, [&](InputSection *S) {
+ if (S->AreRelocsRela)
+ combineRelocHashes(S, S->template relas<ELFT>());
+ else
+ combineRelocHashes(S, S->template rels<ELFT>());
});
// From now on, sections in Sections vector are ordered so that sections
