[lld] r315401 - Inline addRegular into addSymbol.
Rui Ueyama via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 10 18:03:37 PDT 2017
Author: ruiu
Date: Tue Oct 10 18:03:37 2017
New Revision: 315401
URL: http://llvm.org/viewvc/llvm-project?rev=315401&view=rev
Log:
Inline addRegular into addSymbol.
Because addRegular's functionality is tightly coupled with
addSymbol, and the former is called only once, it makes sense
to merge the two functions. This patch also adds comments.
Modified:
lld/trunk/ELF/LinkerScript.cpp
lld/trunk/ELF/LinkerScript.h
Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=315401&r1=315400&r2=315401&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Tue Oct 10 18:03:37 2017
@@ -79,25 +79,6 @@ uint64_t ExprValue::getSectionOffset() c
return getValue() - getSecAddr();
}
-static SymbolBody *addRegular(SymbolAssignment *Cmd) {
- Symbol *Sym;
- uint8_t Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
- std::tie(Sym, std::ignore) = Symtab->insert(Cmd->Name, /*Type*/ 0, Visibility,
- /*CanOmitFromDynSym*/ false,
- /*File*/ nullptr);
- Sym->Binding = STB_GLOBAL;
- ExprValue Value = Cmd->Expression();
- SectionBase *Sec = Value.isAbsolute() ? nullptr : Value.Sec;
-
- // We want to set symbol values early if we can. This allows us to use symbols
- // as variables in linker scripts. Doing so allows us to write expressions
- // like this: `alignment = 16; . = ALIGN(., alignment)`
- uint64_t SymValue = Value.Sec ? 0 : Value.getValue();
- replaceBody<DefinedRegular>(Sym, nullptr, Cmd->Name, /*IsLocal=*/false,
- Visibility, STT_NOTYPE, SymValue, 0, Sec);
- return Sym->body();
-}
-
OutputSection *LinkerScript::createOutputSection(StringRef Name,
StringRef Location) {
OutputSection *&SecRef = NameToOutputSection[Name];
@@ -127,14 +108,55 @@ void LinkerScript::setDot(Expr E, const
error(Loc + ": unable to move location counter backward for: " +
CurAddressState->OutSec->Name);
Dot = Val;
+
// Update to location counter means update to section size.
if (InSec)
CurAddressState->OutSec->Size = Dot - CurAddressState->OutSec->Addr;
}
-// Sets value of a symbol. Two kinds of symbols are processed: synthetic
-// symbols, whose value is an offset from beginning of section and regular
-// symbols whose value is absolute.
+// This function is called from processCommands, while we are
+// fixing the output section layout.
+void LinkerScript::addSymbol(SymbolAssignment *Cmd) {
+ if (Cmd->Name == ".")
+ return;
+
+ // If a symbol was in PROVIDE(), we need to define it only when
+ // it is a referenced undefined symbol.
+ SymbolBody *B = Symtab->find(Cmd->Name);
+ if (Cmd->Provide && (!B || B->isDefined()))
+ return;
+
+ // Define a symbol.
+ Symbol *Sym;
+ uint8_t Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
+ std::tie(Sym, std::ignore) = Symtab->insert(Cmd->Name, /*Type*/ 0, Visibility,
+ /*CanOmitFromDynSym*/ false,
+ /*File*/ nullptr);
+ Sym->Binding = STB_GLOBAL;
+ ExprValue Value = Cmd->Expression();
+ SectionBase *Sec = Value.isAbsolute() ? nullptr : Value.Sec;
+
+ // When this function is called, section addresses have not been
+ // fixed yet. So, we may or may not know the value of the RHS
+ // expression.
+ //
+ // For example, if an expression is `x = 42`, we know x is always 42.
+ // However, if an expression is `x = .`, there's no way to know its
+ // value at the moment.
+ //
+ // We want to set symbol values early if we can. This allows us to
+ // use symbols as variables in linker scripts. Doing so allows us to
+ // write expressions like this: `alignment = 16; . = ALIGN(., alignment)`.
+ uint64_t SymValue = Value.Sec ? 0 : Value.getValue();
+
+ replaceBody<DefinedRegular>(Sym, nullptr, Cmd->Name, /*IsLocal=*/false,
+ Visibility, STT_NOTYPE, SymValue, 0, Sec);
+ Cmd->Sym = cast<DefinedRegular>(Sym->body());
+}
+
+// This function is called from assignAddresses, while we are
+// fixing the output section addresses. This function is supposed
+// to set the final value for a given symbol assignment.
void LinkerScript::assignSymbol(SymbolAssignment *Cmd, bool InSec) {
if (Cmd->Name == ".") {
setDot(Cmd->Expression, Cmd->Location, InSec);
@@ -144,30 +166,16 @@ void LinkerScript::assignSymbol(SymbolAs
if (!Cmd->Sym)
return;
- auto *Sym = cast<DefinedRegular>(Cmd->Sym);
ExprValue V = Cmd->Expression();
if (V.isAbsolute()) {
- Sym->Value = V.getValue();
- Sym->Section = nullptr;
+ Cmd->Sym->Section = nullptr;
+ Cmd->Sym->Value = V.getValue();
} else {
- Sym->Section = V.Sec;
- Sym->Value = V.getSectionOffset();
+ Cmd->Sym->Section = V.Sec;
+ Cmd->Sym->Value = V.getSectionOffset();
}
}
-void LinkerScript::addSymbol(SymbolAssignment *Cmd) {
- if (Cmd->Name == ".")
- return;
-
- // If a symbol was in PROVIDE(), we need to define it only when
- // it is a referenced undefined symbol.
- SymbolBody *B = Symtab->find(Cmd->Name);
- if (Cmd->Provide && (!B || B->isDefined()))
- return;
-
- Cmd->Sym = addRegular(Cmd);
-}
-
bool SymbolAssignment::classof(const BaseCommand *C) {
return C->Kind == AssignmentKind;
}
@@ -359,6 +367,7 @@ void LinkerScript::processCommands(Outpu
Aether = make<OutputSection>("", 0, SHF_ALLOC);
Aether->SectionIndex = 1;
auto State = make_unique<AddressState>(Opt);
+
// CurAddressState captures the local AddressState and makes it accessible
// deliberately. This is needed as there are some cases where we cannot just
// thread the current state through to a lambda function created by the
@@ -785,6 +794,7 @@ void LinkerScript::assignAddresses() {
// -image-base if set.
Dot = Config->ImageBase ? *Config->ImageBase : 0;
auto State = make_unique<AddressState>(Opt);
+
// CurAddressState captures the local AddressState and makes it accessible
// deliberately. This is needed as there are some cases where we cannot just
// thread the current state through to a lambda function created by the
Modified: lld/trunk/ELF/LinkerScript.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.h?rev=315401&r1=315400&r2=315401&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.h (original)
+++ lld/trunk/ELF/LinkerScript.h Tue Oct 10 18:03:37 2017
@@ -28,7 +28,7 @@
namespace lld {
namespace elf {
-class DefinedCommon;
+class DefinedRegular;
class SymbolBody;
class InputSectionBase;
class InputSection;
@@ -93,7 +93,7 @@ struct SymbolAssignment : BaseCommand {
// The LHS of an expression. Name is either a symbol name or ".".
StringRef Name;
- SymbolBody *Sym = nullptr;
+ DefinedRegular *Sym = nullptr;
// The RHS of an expression.
Expr Expression;
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