t.p.northover created this revision.
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Herald added a project: clang.
AArch64 MachO has a compact unwind format where most functions' unwind info can
be represented in just 4 bytes. But this cannot represent any asynchronous CFI
function, so it's essentially disabled when that's used. This is a large
code-size hit that we'd rather not take unless explicitly requested.
So this patch adds a new callback to switch the default on ARM64 MachO to
synchronous. Command-line options can still turn it on if anyone wants to take
the hit.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D131153
Files:
clang/include/clang/Driver/ToolChain.h
clang/lib/Driver/ToolChains/Clang.cpp
clang/lib/Driver/ToolChains/Darwin.cpp
clang/lib/Driver/ToolChains/Darwin.h
clang/test/Driver/clang-translation.c
clang/test/Preprocessor/unwind-tables.c
Index: clang/test/Preprocessor/unwind-tables.c
===================================================================
--- clang/test/Preprocessor/unwind-tables.c
+++ clang/test/Preprocessor/unwind-tables.c
@@ -3,7 +3,7 @@
// RUN: %clang %s -dM -E -target x86_64 | FileCheck %s
// RUN: %clang %s -dM -E -target x86_64 -funwind-tables -fno-asynchronous-unwind-tables -g | FileCheck %s
-// RUN: %clang %s -dM -E -target aarch64-apple-darwin | FileCheck %s
+// RUN: %clang %s -dM -E -target aarch64-apple-darwin | FileCheck %s --check-prefix=NO
// RUN: %clang %s -dM -E -target x86_64 -fno-asynchronous-unwind-tables -g | FileCheck %s
// RUN: %clang %s -dM -E -target x86_64 -fno-asynchronous-unwind-tables -fexceptions | FileCheck %s
Index: clang/test/Driver/clang-translation.c
===================================================================
--- clang/test/Driver/clang-translation.c
+++ clang/test/Driver/clang-translation.c
@@ -78,7 +78,11 @@
// RUN: %clang -target arm64-apple-ios10 -### -S %s -arch arm64 2>&1 | \
// RUN: FileCheck -check-prefix=ARM64-APPLE %s
-// ARM64-APPLE: -funwind-tables=2
+// ARM64-APPLE-NOT: -funwind-tables
+
+// RUN: %clang -target arm64-apple-ios10 -funwind-tables -### -S %s -arch arm64 2>&1 | \
+// RUN: FileCheck -check-prefix=ARM64-APPLE-UNWIND %s
+// ARM64-APPLE-UNWIND: -funwind-tables=1
// RUN: %clang -target arm64-apple-ios10 -### -ffreestanding -S %s -arch arm64 2>&1 | \
// RUN: FileCheck -check-prefix=ARM64-FREESTANDING-APPLE %s
Index: clang/lib/Driver/ToolChains/Darwin.h
===================================================================
--- clang/lib/Driver/ToolChains/Darwin.h
+++ clang/lib/Driver/ToolChains/Darwin.h
@@ -256,6 +256,9 @@
bool IsUnwindTablesDefault(const llvm::opt::ArgList &Args) const override;
+ bool
+ IsAsyncUnwindTablesDefault(const llvm::opt::ArgList &Args) const override;
+
RuntimeLibType GetDefaultRuntimeLibType() const override {
return ToolChain::RLT_CompilerRT;
}
Index: clang/lib/Driver/ToolChains/Darwin.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Darwin.cpp
+++ clang/lib/Driver/ToolChains/Darwin.cpp
@@ -2894,6 +2894,15 @@
true));
}
+bool MachO::IsAsyncUnwindTablesDefault(const ArgList &Args) const {
+ // AArch64 has compact unwind format, making the size overhead from
+ // asynchronous unwind particularly bad, so disable by default.
+ if (getArch() == llvm::Triple::aarch64)
+ return false;
+
+ return IsUnwindTablesDefault(Args);
+}
+
bool MachO::UseDwarfDebugFlags() const {
if (const char *S = ::getenv("RC_DEBUG_OPTIONS"))
return S[0] != '\0';
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -5387,11 +5387,12 @@
// -fasynchronous-unwind-tables and -fnon-call-exceptions interact in more
// complicated ways.
auto SanitizeArgs = TC.getSanitizerArgs(Args);
- bool AsyncUnwindTables = Args.hasFlag(
- options::OPT_fasynchronous_unwind_tables,
- options::OPT_fno_asynchronous_unwind_tables,
- (TC.IsUnwindTablesDefault(Args) || SanitizeArgs.needsUnwindTables()) &&
- !Freestanding);
+ bool AsyncUnwindTables =
+ Args.hasFlag(options::OPT_fasynchronous_unwind_tables,
+ options::OPT_fno_asynchronous_unwind_tables,
+ (TC.IsAsyncUnwindTablesDefault(Args) ||
+ SanitizeArgs.needsUnwindTables()) &&
+ !Freestanding);
bool UnwindTables = Args.hasFlag(options::OPT_funwind_tables,
options::OPT_fno_unwind_tables, false);
if (AsyncUnwindTables)
Index: clang/include/clang/Driver/ToolChain.h
===================================================================
--- clang/include/clang/Driver/ToolChain.h
+++ clang/include/clang/Driver/ToolChain.h
@@ -497,6 +497,13 @@
/// by default.
virtual bool IsUnwindTablesDefault(const llvm::opt::ArgList &Args) const;
+ /// IsAsyncUnwindTablesDefault - Does this tool chain use
+ /// -fasync-unwind-tables by default.
+ virtual bool
+ IsAsyncUnwindTablesDefault(const llvm::opt::ArgList &Args) const {
+ return IsUnwindTablesDefault(Args);
+ }
+
/// Test whether this toolchain supports outline atomics by default.
virtual bool
IsAArch64OutlineAtomicsDefault(const llvm::opt::ArgList &Args) const {
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