[lld] 3ea1c62 - [WebAssembly] Emit .llvmcmd and .llvmbc as custom sections
Sam Clegg via llvm-commits
llvm-commits at lists.llvm.org
Tue Apr 14 13:24:31 PDT 2020
Author: Sam Clegg
Date: 2020-04-14T13:24:18-07:00
New Revision: 3ea1c62cbae2fa89cd49a47879bd63bcfdf3fb9b
URL: https://github.com/llvm/llvm-project/commit/3ea1c62cbae2fa89cd49a47879bd63bcfdf3fb9b
DIFF: https://github.com/llvm/llvm-project/commit/3ea1c62cbae2fa89cd49a47879bd63bcfdf3fb9b.diff
LOG: [WebAssembly] Emit .llvmcmd and .llvmbc as custom sections
Fixes: https://bugs.llvm.org/show_bug.cgi?id=45362
Differential Revision: https://reviews.llvm.org/D77115
Added:
clang/test/Driver/embed-bitcode-wasm.c
Modified:
clang/test/Driver/fembed-bitcode.c
lld/wasm/Writer.cpp
llvm/include/llvm/MC/MCSymbolWasm.h
llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
llvm/lib/MC/WasmObjectWriter.cpp
Removed:
################################################################################
diff --git a/clang/test/Driver/embed-bitcode-wasm.c b/clang/test/Driver/embed-bitcode-wasm.c
new file mode 100644
index 000000000000..3705a4d24875
--- /dev/null
+++ b/clang/test/Driver/embed-bitcode-wasm.c
@@ -0,0 +1,6 @@
+// REQUIRES: webassembly-registered-target
+
+// RUN: %clang -c -target wasm32-unknown-unknown %s -fembed-bitcode -o %t.o
+// RUN: llvm-readobj -S %t.o | FileCheck --check-prefix=CHECK %s
+// CHECK: Name: .llvmbc
+// CHECK: Name: .llvmcmd
diff --git a/clang/test/Driver/fembed-bitcode.c b/clang/test/Driver/fembed-bitcode.c
index d01ae6cd8c18..970500525a50 100644
--- a/clang/test/Driver/fembed-bitcode.c
+++ b/clang/test/Driver/fembed-bitcode.c
@@ -30,3 +30,12 @@
// RUN: | FileCheck --check-prefix=CHECK-HEXAGON %s
// CHECK-HEXAGON: "-target-feature"
// CHECK-HEXAGON: "+reserved-r19"
+//
+// RUN: %clang -target wasm32-unknown-unknown -fembed-bitcode=all -pthread -c %s -o /dev/null -### 2>&1 \
+// RUN: | FileCheck --check-prefix=CHECK-WASM %s
+
+// CHECK-WASM: "-cc1"
+// CHECK-WASM: "-target-feature" "+atomics"
+
+// CHECK-WASM: "-cc1"
+// CHECK-WASM: "-target-feature" "+atomics"
diff --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp
index d1ada22f684a..a6b215344cdb 100644
--- a/lld/wasm/Writer.cpp
+++ b/lld/wasm/Writer.cpp
@@ -110,13 +110,21 @@ void Writer::calculateCustomSections() {
for (InputSection *section : file->customSections) {
StringRef name = section->getName();
// These custom sections are known the linker and synthesized rather than
- // blindly copied
+ // blindly copied.
if (name == "linking" || name == "name" || name == "producers" ||
name == "target_features" || name.startswith("reloc."))
continue;
- // .. or it is a debug section
+ // These custom sections are generated by `clang -fembed-bitcode`.
+ // These are used by the rust toolchain to ship LTO data along with
+ // compiled object code, but they don't want this included in the linker
+ // output.
+ if (name == ".llvmbc" || name == ".llvmcmd")
+ continue;
+ // Strip debug section in that option was specified.
if (stripDebug && name.startswith(".debug_"))
continue;
+ // Otherwise include custom sections by default and concatenate their
+ // contents.
customSectionMapping[name].push_back(section);
}
}
diff --git a/llvm/include/llvm/MC/MCSymbolWasm.h b/llvm/include/llvm/MC/MCSymbolWasm.h
index da9525922fa2..ffd8a7aad312 100644
--- a/llvm/include/llvm/MC/MCSymbolWasm.h
+++ b/llvm/include/llvm/MC/MCSymbolWasm.h
@@ -18,6 +18,7 @@ class MCSymbolWasm : public MCSymbol {
bool IsWeak = false;
bool IsHidden = false;
bool IsComdat = false;
+ mutable bool IsUsedInInitArray = false;
mutable bool IsUsedInGOT = false;
Optional<StringRef> ImportModule;
Optional<StringRef> ImportName;
@@ -96,6 +97,9 @@ class MCSymbolWasm : public MCSymbol {
void setUsedInGOT() const { IsUsedInGOT = true; }
bool isUsedInGOT() const { return IsUsedInGOT; }
+ void setUsedInInitArray() const { IsUsedInInitArray = true; }
+ bool isUsedInInitArray() const { return IsUsedInInitArray; }
+
const wasm::WasmSignature *getSignature() const { return Signature; }
void setSignature(wasm::WasmSignature *Sig) { Signature = Sig; }
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 17946696a26f..e7750ccf3ad8 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -1755,6 +1755,14 @@ MCSection *TargetLoweringObjectFileWasm::getExplicitSectionGlobal(
StringRef Name = GO->getSection();
+ // Certain data sections we treat as named custom sections rather than
+ // segments within the data section.
+ // This could be avoided if all data segements (the wasm sense) were
+ // represented as thier own sections (in the llvm sense).
+ // TODO(sbc): https://github.com/WebAssembly/tool-conventions/issues/138
+ if (Name == ".llvmcmd" || Name == ".llvmbc")
+ Kind = SectionKind::getMetadata();
+
StringRef Group = "";
if (const Comdat *C = getWasmComdat(GO)) {
Group = C->getName();
diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 321f93d76092..4df809224edb 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -436,10 +436,6 @@ void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
MCContext &Ctx = Asm.getContext();
- // The .init_array isn't translated as data, so don't do relocations in it.
- if (FixupSection.getSectionName().startswith(".init_array"))
- return;
-
if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
// To get here the A - B expression must have failed evaluateAsRelocatable.
// This means either A or B must be undefined and in WebAssembly we can't
@@ -456,6 +452,12 @@ void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
const MCSymbolRefExpr *RefA = Target.getSymA();
const auto *SymA = cast<MCSymbolWasm>(&RefA->getSymbol());
+ // The .init_array isn't translated as data, so don't do relocations in it.
+ if (FixupSection.getSectionName().startswith(".init_array")) {
+ SymA->setUsedInInitArray();
+ return;
+ }
+
if (SymA->isVariable()) {
const MCExpr *Expr = SymA->getVariableValue();
const auto *Inner = cast<MCSymbolRefExpr>(Expr);
@@ -1084,16 +1086,13 @@ void WasmObjectWriter::registerEventType(const MCSymbolWasm &Symbol) {
}
static bool isInSymtab(const MCSymbolWasm &Sym) {
- if (Sym.isUsedInReloc())
+ if (Sym.isUsedInReloc() || Sym.isUsedInInitArray())
return true;
if (Sym.isComdat() && !Sym.isDefined())
return false;
- if (Sym.isTemporary() && Sym.getName().empty())
- return false;
-
- if (Sym.isTemporary() && Sym.isData() && !Sym.getSize())
+ if (Sym.isTemporary())
return false;
if (Sym.isSection())
@@ -1565,7 +1564,7 @@ uint64_t WasmObjectWriter::writeObject(MCAssembler &Asm,
report_fatal_error("fixups in .init_array should be symbol references");
const auto &TargetSym = cast<const MCSymbolWasm>(SymRef->getSymbol());
if (TargetSym.getIndex() == InvalidIndex)
- report_fatal_error("symbols in .init_array should exist in symbtab");
+ report_fatal_error("symbols in .init_array should exist in symtab");
if (!TargetSym.isFunction())
report_fatal_error("symbols in .init_array should be for functions");
InitFuncs.push_back(
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