[JITLink] Introduce target flags for Symbol and prepare ObjectLinkingLayer to account for them

AArch32 branch offsets explicitly encode the target instruction subset (Arm/Thumb) in their least significant bit. We want this bit set (or clear) in addreses we hand out, but the addresses in the LinkGraph should be the real/physical addresses.

This patch allows ELFLinkGraphBuilder's to set target-specific flags in jitlink::Symbol and prepares ObjectLinkingLayer to account for them.

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D146641

2 files changed, 28 insertions, 8 deletions

diff --git a/llvm/lib/ExecutionEngine/JITLink/ELFLinkGraphBuilder.h b/llvm/lib/ExecutionEngine/JITLink/ELFLinkGraphBuilder.h
index 26feb8e..9d2d495 100644
--- a/llvm/lib/ExecutionEngine/JITLink/ELFLinkGraphBuilder.h
+++ b/llvm/lib/ExecutionEngine/JITLink/ELFLinkGraphBuilder.h
@@ -112,6 +112,17 @@ protected:
   Expected<std::pair<Linkage, Scope>>
   getSymbolLinkageAndScope(const typename ELFT::Sym &Sym, StringRef Name);
 
+  /// Set the target flags on the given Symbol.
+  virtual TargetFlagsType makeTargetFlags(const typename ELFT::Sym &Sym) {
+    return TargetFlagsType{};
+  }
+
+  /// Get the physical offset of the symbol on the target platform.
+  virtual orc::ExecutorAddrDiff getRawOffset(const typename ELFT::Sym &Sym,
+                                             TargetFlagsType Flags) {
+    return Sym.getValue();
+  }
+
   Error prepare();
   Error graphifySections();
   Error graphifySymbols();
@@ -478,6 +489,9 @@ template <typename ELFT> Error ELFLinkGraphBuilder<ELFT>::graphifySymbols() {
                  << "\"\n";
         });
 
+        TargetFlagsType Flags = makeTargetFlags(Sym);
+        orc::ExecutorAddrDiff Offset = getRawOffset(Sym, Flags);
+
         // In RISCV, temporary symbols (Used to generate dwarf, eh_frame
         // sections...) will appear in object code's symbol table, and LLVM does
         // not use names on these temporary symbols (RISCV gnu toolchain uses
@@ -485,10 +499,13 @@ template <typename ELFT> Error ELFLinkGraphBuilder<ELFT>::graphifySymbols() {
         // anonymous symbol.
         auto &GSym =
             Name->empty()
-                ? G->addAnonymousSymbol(*B, Sym.getValue(), Sym.st_size,
+                ? G->addAnonymousSymbol(*B, Offset, Sym.st_size,
                                         false, false)
-                : G->addDefinedSymbol(*B, Sym.getValue(), *Name, Sym.st_size, L,
-                                      S, Sym.getType() == ELF::STT_FUNC, false);
+                : G->addDefinedSymbol(*B, Offset, *Name, Sym.st_size, L,
+                                      S, Sym.getType() == ELF::STT_FUNC,
+                                      false);
+
+        GSym.setTargetFlags(Flags);
         setGraphSymbol(SymIndex, GSym);
       }
     } else if (Sym.isUndefined() && Sym.isExternal()) {
diff --git a/llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp b/llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp
index e7356e5..2c270cd 100644
--- a/llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp
@@ -39,6 +39,10 @@ bool hasInitializerSection(jitlink::LinkGraph &G) {
   return false;
 }
 
+JITTargetAddress getJITSymbolPtrForSymbol(Symbol &Sym) {
+  return Sym.getAddress().getValue();
+}
+
 JITSymbolFlags getJITSymbolFlagsForSymbol(Symbol &Sym) {
   JITSymbolFlags Flags;
 
@@ -215,10 +219,9 @@ public:
     for (auto *Sym : G.defined_symbols())
       if (Sym->hasName() && Sym->getScope() != Scope::Local) {
         auto InternedName = ES.intern(Sym->getName());
+        auto Ptr = getJITSymbolPtrForSymbol(*Sym);
         auto Flags = getJITSymbolFlagsForSymbol(*Sym);
-
-        InternedResult[InternedName] =
-            JITEvaluatedSymbol(Sym->getAddress().getValue(), Flags);
+        InternedResult[InternedName] = JITEvaluatedSymbol(Ptr, Flags);
         if (AutoClaim && !MR->getSymbols().count(InternedName)) {
           assert(!ExtraSymbolsToClaim.count(InternedName) &&
                  "Duplicate symbol to claim?");
@@ -229,9 +232,9 @@ public:
     for (auto *Sym : G.absolute_symbols())
       if (Sym->hasName() && Sym->getScope() != Scope::Local) {
         auto InternedName = ES.intern(Sym->getName());
+        auto Ptr = getJITSymbolPtrForSymbol(*Sym);
         auto Flags = getJITSymbolFlagsForSymbol(*Sym);
-        InternedResult[InternedName] =
-            JITEvaluatedSymbol(Sym->getAddress().getValue(), Flags);
+        InternedResult[InternedName] = JITEvaluatedSymbol(Ptr, Flags);
         if (AutoClaim && !MR->getSymbols().count(InternedName)) {
           assert(!ExtraSymbolsToClaim.count(InternedName) &&
                  "Duplicate symbol to claim?");