[llvm] 42595bd - [JITLink] Teach aarch64 GOT & PLT table managers to discover existing entries.
Lang Hames via llvm-commits
llvm-commits at lists.llvm.org
Tue Jan 14 00:55:03 PST 2025
Author: Lang Hames
Date: 2025-01-14T19:54:55+11:00
New Revision: 42595bdaefb6b066896c20b69ab66ff2a7fe8477
URL: https://github.com/llvm/llvm-project/commit/42595bdaefb6b066896c20b69ab66ff2a7fe8477
DIFF: https://github.com/llvm/llvm-project/commit/42595bdaefb6b066896c20b69ab66ff2a7fe8477.diff
LOG: [JITLink] Teach aarch64 GOT & PLT table managers to discover existing entries.
aarch64::GOTTableManager and aarch64::PLTTableManager will now look for
existing GOT and PLT sections and re-use existing entries if they're present.
This will be used for an upcoming MachO patch to enable compact unwind support.
Added:
llvm/unittests/ExecutionEngine/JITLink/AArch64Tests.cpp
Modified:
llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h
llvm/lib/ExecutionEngine/JITLink/ELF_aarch64.cpp
llvm/lib/ExecutionEngine/JITLink/MachO_arm64.cpp
llvm/lib/ExecutionEngine/JITLink/aarch64.cpp
llvm/unittests/ExecutionEngine/JITLink/CMakeLists.txt
Removed:
################################################################################
diff --git a/llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h b/llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h
index 62221caa71c9e9..e5e8ef1bab18be 100644
--- a/llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h
+++ b/llvm/include/llvm/ExecutionEngine/JITLink/aarch64.h
@@ -786,6 +786,11 @@ class GOTTableManager : public TableManager<GOTTableManager> {
public:
static StringRef getSectionName() { return "$__GOT"; }
+ GOTTableManager(LinkGraph &G) {
+ if ((GOTSection = G.findSectionByName(getSectionName())))
+ registerExistingEntries();
+ }
+
bool visitEdge(LinkGraph &G, Block *B, Edge &E) {
Edge::Kind KindToSet = Edge::Invalid;
const char *BlockWorkingMem = B->getContent().data();
@@ -848,16 +853,21 @@ class GOTTableManager : public TableManager<GOTTableManager> {
return *GOTSection;
}
+ void registerExistingEntries();
+
Section *GOTSection = nullptr;
};
/// Procedure Linkage Table Builder.
class PLTTableManager : public TableManager<PLTTableManager> {
public:
- PLTTableManager(GOTTableManager &GOT) : GOT(GOT) {}
-
static StringRef getSectionName() { return "$__STUBS"; }
+ PLTTableManager(LinkGraph &G, GOTTableManager &GOT) : GOT(GOT) {
+ if ((StubsSection = G.findSectionByName(getSectionName())))
+ registerExistingEntries();
+ }
+
bool visitEdge(LinkGraph &G, Block *B, Edge &E) {
if (E.getKind() == aarch64::Branch26PCRel && !E.getTarget().isDefined()) {
DEBUG_WITH_TYPE("jitlink", {
@@ -884,6 +894,8 @@ class PLTTableManager : public TableManager<PLTTableManager> {
return *StubsSection;
}
+ void registerExistingEntries();
+
GOTTableManager &GOT;
Section *StubsSection = nullptr;
};
diff --git a/llvm/lib/ExecutionEngine/JITLink/ELF_aarch64.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_aarch64.cpp
index 260a493f0ffd25..b617fe222df003 100644
--- a/llvm/lib/ExecutionEngine/JITLink/ELF_aarch64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/ELF_aarch64.cpp
@@ -659,8 +659,8 @@ const uint8_t TLSDescTableManager_ELF_aarch64::TLSDescEntryContent[16] = {
Error buildTables_ELF_aarch64(LinkGraph &G) {
LLVM_DEBUG(dbgs() << "Visiting edges in graph:\n");
- aarch64::GOTTableManager GOT;
- aarch64::PLTTableManager PLT(GOT);
+ aarch64::GOTTableManager GOT(G);
+ aarch64::PLTTableManager PLT(G, GOT);
TLSInfoTableManager_ELF_aarch64 TLSInfo;
TLSDescTableManager_ELF_aarch64 TLSDesc(TLSInfo);
visitExistingEdges(G, GOT, PLT, TLSDesc, TLSInfo);
diff --git a/llvm/lib/ExecutionEngine/JITLink/MachO_arm64.cpp b/llvm/lib/ExecutionEngine/JITLink/MachO_arm64.cpp
index 8b43dc97e49a81..29061fff9c2aea 100644
--- a/llvm/lib/ExecutionEngine/JITLink/MachO_arm64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/MachO_arm64.cpp
@@ -558,8 +558,8 @@ namespace jitlink {
Error buildTables_MachO_arm64(LinkGraph &G) {
LLVM_DEBUG(dbgs() << "Visiting edges in graph:\n");
- aarch64::GOTTableManager GOT;
- aarch64::PLTTableManager PLT(GOT);
+ aarch64::GOTTableManager GOT(G);
+ aarch64::PLTTableManager PLT(G, GOT);
visitExistingEdges(G, GOT, PLT);
return Error::success();
}
diff --git a/llvm/lib/ExecutionEngine/JITLink/aarch64.cpp b/llvm/lib/ExecutionEngine/JITLink/aarch64.cpp
index 968ed217d8a963..e2364ad786a42f 100644
--- a/llvm/lib/ExecutionEngine/JITLink/aarch64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/aarch64.cpp
@@ -202,6 +202,26 @@ static Error writeStoreRegSeq(AppendFtor &Append, unsigned DstLocReg,
return Append(Instr);
}
+void GOTTableManager::registerExistingEntries() {
+ for (auto *EntrySym : GOTSection->symbols()) {
+ assert(EntrySym->getBlock().edges_size() == 1 &&
+ "GOT block edge count != 1");
+ registerPreExistingEntry(EntrySym->getBlock().edges().begin()->getTarget(),
+ *EntrySym);
+ }
+}
+
+void PLTTableManager::registerExistingEntries() {
+ for (auto *EntrySym : StubsSection->symbols()) {
+ assert(EntrySym->getBlock().edges_size() == 2 &&
+ "PLT block edge count != 2");
+ auto &GOTSym = EntrySym->getBlock().edges().begin()->getTarget();
+ assert(GOTSym.getBlock().edges_size() == 1 && "GOT block edge count != 1");
+ registerPreExistingEntry(GOTSym.getBlock().edges().begin()->getTarget(),
+ *EntrySym);
+ }
+}
+
const char *getPointerSigningFunctionSectionName() { return "$__ptrauth_sign"; }
/// Creates a pointer signing function section, block, and symbol to reserve
diff --git a/llvm/unittests/ExecutionEngine/JITLink/AArch64Tests.cpp b/llvm/unittests/ExecutionEngine/JITLink/AArch64Tests.cpp
new file mode 100644
index 00000000000000..34918ead5b49b8
--- /dev/null
+++ b/llvm/unittests/ExecutionEngine/JITLink/AArch64Tests.cpp
@@ -0,0 +1,90 @@
+//===------- AArch64Tests.cpp - Unit tests for the AArch64 backend --------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <llvm/BinaryFormat/ELF.h>
+#include <llvm/ExecutionEngine/JITLink/aarch64.h>
+
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace llvm::jitlink;
+using namespace llvm::jitlink::aarch64;
+
+TEST(AArch64, EmptyLinkGraph) {
+ LinkGraph G("foo", std::make_shared<orc::SymbolStringPool>(),
+ Triple("arm64-apple-darwin"), SubtargetFeatures(),
+ getEdgeKindName);
+ EXPECT_EQ(G.getName(), "foo");
+ EXPECT_EQ(G.getTargetTriple().str(), "arm64-apple-darwin");
+ EXPECT_EQ(G.getPointerSize(), 8U);
+ EXPECT_EQ(G.getEndianness(), llvm::endianness::little);
+ EXPECT_TRUE(G.external_symbols().empty());
+ EXPECT_TRUE(G.absolute_symbols().empty());
+ EXPECT_TRUE(G.defined_symbols().empty());
+ EXPECT_TRUE(G.blocks().empty());
+}
+
+TEST(AArch64, GOTAndStubs) {
+ LinkGraph G("foo", std::make_shared<orc::SymbolStringPool>(),
+ Triple("arm64-apple-darwin"), SubtargetFeatures(),
+ getEdgeKindName);
+
+ auto &External = G.addExternalSymbol("external", 0, false);
+
+ // First table accesses. We expect the graph to be empty:
+ EXPECT_EQ(G.findSectionByName(GOTTableManager::getSectionName()), nullptr);
+ EXPECT_EQ(G.findSectionByName(PLTTableManager::getSectionName()), nullptr);
+
+ {
+ // Create first GOT and PLT table managers and request a PLT stub. This
+ // should force creation of both a PLT stub and GOT entry.
+ GOTTableManager GOT(G);
+ PLTTableManager PLT(G, GOT);
+
+ PLT.getEntryForTarget(G, External);
+ }
+
+ auto *GOTSec = G.findSectionByName(GOTTableManager::getSectionName());
+ EXPECT_NE(GOTSec, nullptr);
+ if (GOTSec) {
+ // Expect one entry in the GOT now.
+ EXPECT_EQ(GOTSec->symbols_size(), 1U);
+ EXPECT_EQ(GOTSec->blocks_size(), 1U);
+ }
+
+ auto *PLTSec = G.findSectionByName(PLTTableManager::getSectionName());
+ EXPECT_NE(PLTSec, nullptr);
+ if (PLTSec) {
+ // Expect one entry in the PLT.
+ EXPECT_EQ(PLTSec->symbols_size(), 1U);
+ EXPECT_EQ(PLTSec->blocks_size(), 1U);
+ }
+
+ {
+ // Create second GOT and PLT table managers and request a PLT stub. This
+ // should force creation of both a PLT stub and GOT entry.
+ GOTTableManager GOT(G);
+ PLTTableManager PLT(G, GOT);
+
+ PLT.getEntryForTarget(G, External);
+ }
+
+ EXPECT_EQ(G.findSectionByName(GOTTableManager::getSectionName()), GOTSec);
+ if (GOTSec) {
+ // Expect the same one entry in the GOT.
+ EXPECT_EQ(GOTSec->symbols_size(), 1U);
+ EXPECT_EQ(GOTSec->blocks_size(), 1U);
+ }
+
+ EXPECT_EQ(G.findSectionByName(PLTTableManager::getSectionName()), PLTSec);
+ if (PLTSec) {
+ // Expect the same one entry in the GOT.
+ EXPECT_EQ(PLTSec->symbols_size(), 1U);
+ EXPECT_EQ(PLTSec->blocks_size(), 1U);
+ }
+}
diff --git a/llvm/unittests/ExecutionEngine/JITLink/CMakeLists.txt b/llvm/unittests/ExecutionEngine/JITLink/CMakeLists.txt
index d1c7b799880a3b..bbf6b1bf1e0edb 100644
--- a/llvm/unittests/ExecutionEngine/JITLink/CMakeLists.txt
+++ b/llvm/unittests/ExecutionEngine/JITLink/CMakeLists.txt
@@ -10,6 +10,7 @@ set(LLVM_LINK_COMPONENTS
add_llvm_unittest(JITLinkTests
AArch32Tests.cpp
AArch32ErrorTests.cpp
+ AArch64Tests.cpp
EHFrameSupportTests.cpp
JITLinkTestUtils.cpp
LinkGraphTests.cpp
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