CodeGen: handle llvm.used properly for COFF
`llvm.used` contains a list of pointers to named values which the
compiler, assembler, and linker are required to treat as if there is a
reference that they cannot see. Ensure that the symbols are preserved
by adding an explicit `-include` reference to the linker command.
llvm-svn: 323017
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 2a20c64..87d9137 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1434,6 +1434,7 @@
// Emit /EXPORT: flags for each exported global as necessary.
const auto &TLOF = getObjFileLowering();
std::string Flags;
+
for (const GlobalValue &GV : M.global_values()) {
raw_string_ostream OS(Flags);
TLOF.emitLinkerFlagsForGlobal(OS, &GV);
@@ -1444,6 +1445,35 @@
}
Flags.clear();
}
+
+ // Emit /INCLUDE: flags for each used global as necessary.
+ if (const auto *LU = M.getNamedGlobal("llvm.used")) {
+ assert(LU->hasInitializer() &&
+ "expected llvm.used to have an initializer");
+ assert(isa<ArrayType>(LU->getValueType()) &&
+ "expected llvm.used to be an array type");
+ if (const auto *A = cast<ConstantArray>(LU->getInitializer())) {
+ for (const Value *Op : A->operands()) {
+ const auto *GV =
+ cast<GlobalValue>(Op->stripPointerCastsNoFollowAliases());
+ // Global symbols with internal linkage are not visible to the linker,
+ // and thus would cause an error when the linker tried to preserve the
+ // symbol due to the `/include:` directive.
+ if (GV->hasInternalLinkage())
+ continue;
+
+ raw_string_ostream OS(Flags);
+ TLOF.emitLinkerFlagsForUsed(OS, GV);
+ OS.flush();
+
+ if (!Flags.empty()) {
+ OutStreamer->SwitchSection(TLOF.getDrectveSection());
+ OutStreamer->EmitBytes(Flags);
+ }
+ Flags.clear();
+ }
+ }
+ }
}
// Allow the target to emit any magic that it wants at the end of the file,
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index bdc4bc0..0e90df9 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -1250,6 +1250,11 @@
emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
}
+void TargetLoweringObjectFileCOFF::emitLinkerFlagsForUsed(
+ raw_ostream &OS, const GlobalValue *GV) const {
+ emitLinkerFlagsForUsedCOFF(OS, GV, getTargetTriple(), getMangler());
+}
+
//===----------------------------------------------------------------------===//
// Wasm
//===----------------------------------------------------------------------===//