[llvm] [lldb] [clang] [BOLT] Extend calculateEmittedSize for Block Size Calculation (PR #73076)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Nov 22 08:53:49 PST 2023
https://github.com/ShatianWang updated https://github.com/llvm/llvm-project/pull/73076
>From 322c9ed213a0aa674d822a01e8b809eb1be628a5 Mon Sep 17 00:00:00 2001
From: Amir Ayupov <aaupov at meta.com>
Date: Tue, 1 Jun 2021 11:37:41 -0700
Subject: [PATCH 1/3] Rebase: [Facebook] Add clang driver options to test debug
info and BOLT
Summary:
This is an essential piece of infrastructure for us to be
continuously testing debug info with BOLT. We can't only make changes
to a test repo because we need to change debuginfo tests to call BOLT,
hence, this diff needs to sit in our opensource repo. But when upstreaming
to LLVM, this should be kept BOLT-only outside of LLVM. When upstreaming,
we need to git diff and check all folders that are being modified by our
commits and discard this one (and leave as an internal diff).
To test BOLT in debuginfo tests, configure it with -DLLVM_TEST_BOLT=ON.
Then run check-lldb and check-debuginfo.
Manual rebase conflict history:
https://phabricator.intern.facebook.com/D29205224
https://phabricator.intern.facebook.com/D29564078
https://phabricator.intern.facebook.com/D33289118
https://phabricator.intern.facebook.com/D34957174
https://phabricator.intern.facebook.com/D35317341
Test Plan:
tested locally
Configured with:
-DLLVM_ENABLE_PROJECTS="clang;lld;lldb;compiler-rt;bolt;debuginfo-tests"
-DLLVM_TEST_BOLT=ON
Ran test suite with:
ninja check-debuginfo
ninja check-lldb
Reviewers: maks, #llvm-bolt
Reviewed By: maks
Subscribers: ayermolo, phabricatorlinter
Differential Revision: https://phabricator.intern.facebook.com/D46256657
Tasks: T92898286
---
clang/include/clang/Driver/Options.td | 4 ++++
clang/lib/Driver/ToolChains/Gnu.cpp | 29 ++++++++++++++++++++++++++
cross-project-tests/lit.cfg.py | 14 ++++++++++++-
cross-project-tests/lit.site.cfg.py.in | 4 ++++
lldb/test/API/lit.cfg.py | 5 +++++
lldb/test/API/lit.site.cfg.py.in | 8 +++++++
lldb/test/Shell/helper/toolchain.py | 5 +++++
lldb/test/Shell/lit.site.cfg.py.in | 9 ++++++++
llvm/CMakeLists.txt | 4 ++++
9 files changed, 81 insertions(+), 1 deletion(-)
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index b2f2bcb6ac379109..c1a06aab30534fd4 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -5199,6 +5199,10 @@ def pg : Flag<["-"], "pg">, HelpText<"Enable mcount instrumentation">,
MarshallingInfoFlag<CodeGenOpts<"InstrumentForProfiling">>;
def pipe : Flag<["-", "--"], "pipe">,
HelpText<"Use pipes between commands, when possible">;
+// Facebook T92898286
+def post_link_optimize : Flag<["--"], "post-link-optimize">,
+ HelpText<"Apply post-link optimizations using BOLT">;
+// End Facebook T92898286
def prebind__all__twolevel__modules : Flag<["-"], "prebind_all_twolevel_modules">;
def prebind : Flag<["-"], "prebind">;
def preload : Flag<["-"], "preload">;
diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index 2b1e8f02cf663885..07f2d90c82386497 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -662,12 +662,41 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
}
}
+ // Facebook T92898286
+ if (Args.hasArg(options::OPT_post_link_optimize))
+ CmdArgs.push_back("-q");
+ // End Facebook T92898286
+
Args.AddAllArgs(CmdArgs, options::OPT_T);
const char *Exec = Args.MakeArgString(ToolChain.GetLinkerPath());
C.addCommand(std::make_unique<Command>(JA, *this,
ResponseFileSupport::AtFileCurCP(),
Exec, CmdArgs, Inputs, Output));
+ // Facebook T92898286
+ if (!Args.hasArg(options::OPT_post_link_optimize) || !Output.isFilename())
+ return;
+
+ const char *MvExec = Args.MakeArgString(ToolChain.GetProgramPath("mv"));
+ ArgStringList MoveCmdArgs;
+ MoveCmdArgs.push_back(Output.getFilename());
+ const char *PreBoltBin =
+ Args.MakeArgString(Twine(Output.getFilename()) + ".pre-bolt");
+ MoveCmdArgs.push_back(PreBoltBin);
+ C.addCommand(std::make_unique<Command>(JA, *this, ResponseFileSupport::None(),
+ MvExec, MoveCmdArgs, std::nullopt));
+
+ ArgStringList BoltCmdArgs;
+ const char *BoltExec =
+ Args.MakeArgString(ToolChain.GetProgramPath("llvm-bolt"));
+ BoltCmdArgs.push_back(PreBoltBin);
+ BoltCmdArgs.push_back("-reorder-blocks=reverse");
+ BoltCmdArgs.push_back("-update-debug-sections");
+ BoltCmdArgs.push_back("-o");
+ BoltCmdArgs.push_back(Output.getFilename());
+ C.addCommand(std::make_unique<Command>(JA, *this, ResponseFileSupport::None(),
+ BoltExec, BoltCmdArgs, std::nullopt));
+ // End Facebook T92898286
}
void tools::gnutools::Assembler::ConstructJob(Compilation &C,
diff --git a/cross-project-tests/lit.cfg.py b/cross-project-tests/lit.cfg.py
index 774c4eaf4d976b26..619634578dfe609a 100644
--- a/cross-project-tests/lit.cfg.py
+++ b/cross-project-tests/lit.cfg.py
@@ -84,7 +84,13 @@ def get_required_attr(config, attr_name):
# use_clang() and use_lld() respectively, so set them to "", if needed.
if not hasattr(config, "clang_src_dir"):
config.clang_src_dir = ""
-llvm_config.use_clang(required=("clang" in config.llvm_enabled_projects))
+# Facebook T92898286
+should_test_bolt = get_required_attr(config, "llvm_test_bolt")
+if should_test_bolt:
+ llvm_config.use_clang(required=("clang" in config.llvm_enabled_projects), additional_flags=["--post-link-optimize"])
+else:
+ llvm_config.use_clang(required=("clang" in config.llvm_enabled_projects))
+# End Facebook T92898286
if not hasattr(config, "lld_src_dir"):
config.lld_src_dir = ""
@@ -293,3 +299,9 @@ def get_clang_default_dwarf_version_string(triple):
# Allow 'REQUIRES: XXX-registered-target' in tests.
for arch in config.targets_to_build:
config.available_features.add(arch.lower() + "-registered-target")
+
+# Facebook T92898286
+# Ensure the user's PYTHONPATH is included.
+if "PYTHONPATH" in os.environ:
+ config.environment["PYTHONPATH"] = os.environ["PYTHONPATH"]
+# End Facebook T92898286
diff --git a/cross-project-tests/lit.site.cfg.py.in b/cross-project-tests/lit.site.cfg.py.in
index 39458dfc79afd2ad..2d53cd377f0330de 100644
--- a/cross-project-tests/lit.site.cfg.py.in
+++ b/cross-project-tests/lit.site.cfg.py.in
@@ -21,6 +21,10 @@ config.mlir_src_root = "@MLIR_SOURCE_DIR@"
config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
+# Facebook T92898286
+config.llvm_test_bolt = lit.util.pythonize_bool("@LLVM_TEST_BOLT@")
+# End Facebook T92898286
+
import lit.llvm
lit.llvm.initialize(lit_config, config)
diff --git a/lldb/test/API/lit.cfg.py b/lldb/test/API/lit.cfg.py
index 8b35e8b2a217cf7c..3c0c6baa6f55d8a5 100644
--- a/lldb/test/API/lit.cfg.py
+++ b/lldb/test/API/lit.cfg.py
@@ -244,6 +244,11 @@ def delete_module_cache(path):
if is_configured("lldb_framework_dir"):
dotest_cmd += ["--framework", config.lldb_framework_dir]
+# Facebook T92898286
+if is_configured("llvm_test_bolt"):
+ dotest_cmd += ["-E", '"--post-link-optimize"']
+# End Facebook T92898286
+
if (
"lldb-repro-capture" in config.available_features
or "lldb-repro-replay" in config.available_features
diff --git a/lldb/test/API/lit.site.cfg.py.in b/lldb/test/API/lit.site.cfg.py.in
index 053331dc4881f77c..1da91d8fb5508ce9 100644
--- a/lldb/test/API/lit.site.cfg.py.in
+++ b/lldb/test/API/lit.site.cfg.py.in
@@ -1,5 +1,9 @@
@LIT_SITE_CFG_IN_HEADER@
+#Facebook T92898286
+import lit.util
+#End Facebook T92898286
+
config.llvm_src_root = "@LLVM_SOURCE_DIR@"
config.llvm_obj_root = "@LLVM_BINARY_DIR@"
config.llvm_tools_dir = lit_config.substitute("@LLVM_TOOLS_DIR@")
@@ -39,6 +43,10 @@ config.libcxx_include_target_dir = "@LIBCXX_GENERATED_INCLUDE_TARGET_DIR@"
config.lldb_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_LLDB@", "lldb-api")
config.clang_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_CLANG@", "lldb-api")
+# Facebook T92898286
+config.llvm_test_bolt = lit.util.pythonize_bool("@LLVM_TEST_BOLT@")
+# End Facebook T92898286
+
# Plugins
lldb_build_intel_pt = '@LLDB_BUILD_INTEL_PT@'
if lldb_build_intel_pt == '1':
diff --git a/lldb/test/Shell/helper/toolchain.py b/lldb/test/Shell/helper/toolchain.py
index 255955fc70d8c417..7b7be06643166dfb 100644
--- a/lldb/test/Shell/helper/toolchain.py
+++ b/lldb/test/Shell/helper/toolchain.py
@@ -165,6 +165,11 @@ def use_support_substitutions(config):
if config.cmake_sysroot:
host_flags += ["--sysroot={}".format(config.cmake_sysroot)]
+ # Facebook T92898286
+ if config.llvm_test_bolt:
+ host_flags += ["--post-link-optimize"]
+ # End Facebook T92898286
+
host_flags = " ".join(host_flags)
config.substitutions.append(("%clang_host", "%clang " + host_flags))
config.substitutions.append(("%clangxx_host", "%clangxx " + host_flags))
diff --git a/lldb/test/Shell/lit.site.cfg.py.in b/lldb/test/Shell/lit.site.cfg.py.in
index 736dfc335732b5af..3b4d99aa076a4556 100644
--- a/lldb/test/Shell/lit.site.cfg.py.in
+++ b/lldb/test/Shell/lit.site.cfg.py.in
@@ -1,5 +1,10 @@
@LIT_SITE_CFG_IN_HEADER@
+#Facebook T92898286
+import lit.util
+#End Facebook T92898286
+
+
config.llvm_src_root = "@LLVM_SOURCE_DIR@"
config.llvm_obj_root = "@LLVM_BINARY_DIR@"
config.llvm_tools_dir = lit_config.substitute("@LLVM_TOOLS_DIR@")
@@ -30,6 +35,10 @@ config.lldb_system_debugserver = @LLDB_USE_SYSTEM_DEBUGSERVER@
config.lldb_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_LLDB@", "lldb-shell")
config.clang_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_CLANG@", "lldb-shell")
+# Facebook T92898286
+config.llvm_test_bolt = lit.util.pythonize_bool("@LLVM_TEST_BOLT@")
+# End Facebook T92898286
+
import lit.llvm
lit.llvm.initialize(lit_config, config)
diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index 1c983165b2ef0039..cba26c7a617fa4ae 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -685,6 +685,10 @@ set(LLVM_LIB_FUZZING_ENGINE "" CACHE PATH
option(LLVM_USE_SPLIT_DWARF
"Use -gsplit-dwarf when compiling llvm and --gdb-index when linking." OFF)
+# Facebook T92898286
+option(LLVM_TEST_BOLT "Enable BOLT testing in non-BOLT tests that use clang" OFF)
+# End Facebook T92898286
+
# Define an option controlling whether we should build for 32-bit on 64-bit
# platforms, where supported.
if( CMAKE_SIZEOF_VOID_P EQUAL 8 AND NOT (WIN32 OR ${CMAKE_SYSTEM_NAME} MATCHES "AIX"))
>From 18261da423f951b638cd491f391ab206ea17beb8 Mon Sep 17 00:00:00 2001
From: Rafael Auler <rafaelauler at fb.com>
Date: Thu, 5 Aug 2021 14:17:07 -0700
Subject: [PATCH 2/3] Rebase: [Facebook] [MC] Introduce NeverAlign fragment
type
Summary:
Introduce NeverAlign fragment type.
The intended usage of this fragment is to insert it before a pair of
macro-op fusion eligible instructions. NeverAlign fragment ensures that
the next fragment (first instruction in the pair) does not end at a
given alignment boundary by emitting a minimal size nop if necessary.
In effect, it ensures that a pair of macro-fusible instructions is not
split by a given alignment boundary, which is a precondition for
macro-op fusion in modern Intel Cores (64B = cache line size, see Intel
Architecture Optimization Reference Manual, 2.3.2.1 Legacy Decode
Pipeline: Macro-Fusion).
This patch introduces functionality used by BOLT when emitting code with
MacroFusion alignment already in place.
The use case is different from BoundaryAlign and instruction bundling:
- BoundaryAlign can be extended to perform the desired alignment for the
first instruction in the macro-op fusion pair (D101817). However, this
approach has higher overhead due to reliance on relaxation as
BoundaryAlign requires in the general case - see
https://reviews.llvm.org/D97982#2710638.
- Instruction bundling: the intent of NeverAlign fragment is to prevent
the first instruction in a pair ending at a given alignment boundary, by
inserting at most one minimum size nop. It's OK if either instruction
crosses the cache line. Padding both instructions using bundles to not
cross the alignment boundary would result in excessive padding. There's
no straightforward way to request instruction bundling to avoid a given
end alignment for the first instruction in the bundle.
LLVM: https://reviews.llvm.org/D97982
Manual rebase conflict history:
https://phabricator.intern.facebook.com/D30142613
Test Plan: sandcastle
Reviewers: #llvm-bolt
Subscribers: phabricatorlinter
Differential Revision: https://phabricator.intern.facebook.com/D31361547
---
bolt/lib/Core/BinaryEmitter.cpp | 1 +
llvm/include/llvm/MC/MCFragment.h | 22 ++
llvm/include/llvm/MC/MCObjectStreamer.h | 2 +
llvm/include/llvm/MC/MCStreamer.h | 6 +
llvm/lib/MC/MCAssembler.cpp | 118 ++++++----
llvm/lib/MC/MCFragment.cpp | 12 +
llvm/lib/MC/MCObjectStreamer.cpp | 5 +
llvm/lib/MC/MCStreamer.cpp | 2 +
.../lib/Target/X86/AsmParser/X86AsmParser.cpp | 24 ++
llvm/test/MC/X86/directive-avoid_end_align.s | 208 ++++++++++++++++++
10 files changed, 363 insertions(+), 37 deletions(-)
create mode 100644 llvm/test/MC/X86/directive-avoid_end_align.s
diff --git a/bolt/lib/Core/BinaryEmitter.cpp b/bolt/lib/Core/BinaryEmitter.cpp
index fb1bf530c1974aa2..82fbd8c0f67b215f 100644
--- a/bolt/lib/Core/BinaryEmitter.cpp
+++ b/bolt/lib/Core/BinaryEmitter.cpp
@@ -482,6 +482,7 @@ void BinaryEmitter::emitFunctionBody(BinaryFunction &BF, FunctionFragment &FF,
// This assumes the second instruction in the macro-op pair will get
// assigned to its own MCRelaxableFragment. Since all JCC instructions
// are relaxable, we should be safe.
+ Streamer.emitNeverAlignCodeAtEnd(/*Alignment to avoid=*/64, *BC.STI);
}
if (!EmitCodeOnly) {
diff --git a/llvm/include/llvm/MC/MCFragment.h b/llvm/include/llvm/MC/MCFragment.h
index c314fdd3aa69730d..806ba0dc5fe28b49 100644
--- a/llvm/include/llvm/MC/MCFragment.h
+++ b/llvm/include/llvm/MC/MCFragment.h
@@ -33,6 +33,7 @@ class MCFragment : public ilist_node_with_parent<MCFragment, MCSection> {
public:
enum FragmentType : uint8_t {
FT_Align,
+ FT_NeverAlign,
FT_Data,
FT_CompactEncodedInst,
FT_Fill,
@@ -344,6 +345,27 @@ class MCAlignFragment : public MCFragment {
}
};
+class MCNeverAlignFragment : public MCFragment {
+ /// The alignment the end of the next fragment should avoid.
+ unsigned Alignment;
+
+ /// When emitting Nops some subtargets have specific nop encodings.
+ const MCSubtargetInfo &STI;
+
+public:
+ MCNeverAlignFragment(unsigned Alignment, const MCSubtargetInfo &STI,
+ MCSection *Sec = nullptr)
+ : MCFragment(FT_NeverAlign, false, Sec), Alignment(Alignment), STI(STI) {}
+
+ unsigned getAlignment() const { return Alignment; }
+
+ const MCSubtargetInfo &getSubtargetInfo() const { return STI; }
+
+ static bool classof(const MCFragment *F) {
+ return F->getKind() == MCFragment::FT_NeverAlign;
+ }
+};
+
class MCFillFragment : public MCFragment {
uint8_t ValueSize;
/// Value to use for filling bytes.
diff --git a/llvm/include/llvm/MC/MCObjectStreamer.h b/llvm/include/llvm/MC/MCObjectStreamer.h
index 5e5b4b3150170954..3c6fd9301647db7c 100644
--- a/llvm/include/llvm/MC/MCObjectStreamer.h
+++ b/llvm/include/llvm/MC/MCObjectStreamer.h
@@ -157,6 +157,8 @@ class MCObjectStreamer : public MCStreamer {
unsigned MaxBytesToEmit = 0) override;
void emitCodeAlignment(Align ByteAlignment, const MCSubtargetInfo *STI,
unsigned MaxBytesToEmit = 0) override;
+ void emitNeverAlignCodeAtEnd(unsigned ByteAlignment,
+ const MCSubtargetInfo &STI) override;
void emitValueToOffset(const MCExpr *Offset, unsigned char Value,
SMLoc Loc) override;
void emitDwarfLocDirective(unsigned FileNo, unsigned Line, unsigned Column,
diff --git a/llvm/include/llvm/MC/MCStreamer.h b/llvm/include/llvm/MC/MCStreamer.h
index 3bf2d22e182353ff..87691a6ec0e08dd8 100644
--- a/llvm/include/llvm/MC/MCStreamer.h
+++ b/llvm/include/llvm/MC/MCStreamer.h
@@ -885,6 +885,12 @@ class MCStreamer {
virtual void emitCodeAlignment(Align Alignment, const MCSubtargetInfo *STI,
unsigned MaxBytesToEmit = 0);
+ /// If the end of the fragment following this NeverAlign fragment ever gets
+ /// aligned to \p ByteAlignment, this fragment emits a single nop before the
+ /// following fragment to break this end-alignment.
+ virtual void emitNeverAlignCodeAtEnd(unsigned ByteAlignment,
+ const MCSubtargetInfo &STI);
+
/// Emit some number of copies of \p Value until the byte offset \p
/// Offset is reached.
///
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index 901a66f156663f83..15c8b016fef6094a 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -297,6 +297,43 @@ bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
return IsResolved;
}
+/// Check if the branch crosses the boundary.
+///
+/// \param StartAddr start address of the fused/unfused branch.
+/// \param Size size of the fused/unfused branch.
+/// \param BoundaryAlignment alignment requirement of the branch.
+/// \returns true if the branch cross the boundary.
+static bool mayCrossBoundary(uint64_t StartAddr, uint64_t Size,
+ Align BoundaryAlignment) {
+ uint64_t EndAddr = StartAddr + Size;
+ return (StartAddr >> Log2(BoundaryAlignment)) !=
+ ((EndAddr - 1) >> Log2(BoundaryAlignment));
+}
+
+/// Check if the branch is against the boundary.
+///
+/// \param StartAddr start address of the fused/unfused branch.
+/// \param Size size of the fused/unfused branch.
+/// \param BoundaryAlignment alignment requirement of the branch.
+/// \returns true if the branch is against the boundary.
+static bool isAgainstBoundary(uint64_t StartAddr, uint64_t Size,
+ Align BoundaryAlignment) {
+ uint64_t EndAddr = StartAddr + Size;
+ return (EndAddr & (BoundaryAlignment.value() - 1)) == 0;
+}
+
+/// Check if the branch needs padding.
+///
+/// \param StartAddr start address of the fused/unfused branch.
+/// \param Size size of the fused/unfused branch.
+/// \param BoundaryAlignment alignment requirement of the branch.
+/// \returns true if the branch needs padding.
+static bool needPadding(uint64_t StartAddr, uint64_t Size,
+ Align BoundaryAlignment) {
+ return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) ||
+ isAgainstBoundary(StartAddr, Size, BoundaryAlignment);
+}
+
uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
const MCFragment &F) const {
assert(getBackendPtr() && "Requires assembler backend");
@@ -357,6 +394,41 @@ uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
return Size;
}
+ case MCFragment::FT_NeverAlign: {
+ // Disclaimer: NeverAlign fragment size depends on the size of its immediate
+ // successor, but NeverAlign need not be a MCRelaxableFragment.
+ // NeverAlign fragment size is recomputed if the successor is relaxed:
+ // - If RelaxableFragment is relaxed, it gets invalidated by marking its
+ // predecessor as LastValidFragment.
+ // - This forces the assembler to call MCAsmLayout::layoutFragment on that
+ // relaxable fragment, which in turn will always ask the predecessor to
+ // compute its size (see "computeFragmentSize(prev)" in layoutFragment).
+ //
+ // In short, the simplest way to ensure that computeFragmentSize() is sane
+ // is to establish the following rule: it should never examine fragments
+ // after the current fragment in the section. If we logically need to
+ // examine any fragment after the current fragment, we need to do that using
+ // relaxation, inside MCAssembler::layoutSectionOnce.
+ const MCNeverAlignFragment &NAF = cast<MCNeverAlignFragment>(F);
+ const MCFragment *NF = F.getNextNode();
+ uint64_t Offset = Layout.getFragmentOffset(&NAF);
+ size_t NextFragSize = 0;
+ if (const auto *NextFrag = dyn_cast<MCRelaxableFragment>(NF)) {
+ NextFragSize = NextFrag->getContents().size();
+ } else if (const auto *NextFrag = dyn_cast<MCDataFragment>(NF)) {
+ NextFragSize = NextFrag->getContents().size();
+ } else {
+ llvm_unreachable("Didn't find the expected fragment after NeverAlign");
+ }
+ // Check if the next fragment ends at the alignment we want to avoid.
+ if (isAgainstBoundary(Offset, NextFragSize, Align(NAF.getAlignment()))) {
+ // Avoid this alignment by introducing minimum nop.
+ assert(getBackend().getMinimumNopSize() != NAF.getAlignment());
+ return getBackend().getMinimumNopSize();
+ }
+ return 0;
+ }
+
case MCFragment::FT_Org: {
const MCOrgFragment &OF = cast<MCOrgFragment>(F);
MCValue Value;
@@ -580,6 +652,15 @@ static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
break;
}
+ case MCFragment::FT_NeverAlign: {
+ const MCNeverAlignFragment &NAF = cast<MCNeverAlignFragment>(F);
+ if (!Asm.getBackend().writeNopData(OS, FragmentSize,
+ &NAF.getSubtargetInfo()))
+ report_fatal_error("unable to write nop sequence of " +
+ Twine(FragmentSize) + " bytes");
+ break;
+ }
+
case MCFragment::FT_Data:
++stats::EmittedDataFragments;
OS << cast<MCDataFragment>(F).getContents();
@@ -1046,43 +1127,6 @@ bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
return OldSize != LF.getContents().size();
}
-/// Check if the branch crosses the boundary.
-///
-/// \param StartAddr start address of the fused/unfused branch.
-/// \param Size size of the fused/unfused branch.
-/// \param BoundaryAlignment alignment requirement of the branch.
-/// \returns true if the branch cross the boundary.
-static bool mayCrossBoundary(uint64_t StartAddr, uint64_t Size,
- Align BoundaryAlignment) {
- uint64_t EndAddr = StartAddr + Size;
- return (StartAddr >> Log2(BoundaryAlignment)) !=
- ((EndAddr - 1) >> Log2(BoundaryAlignment));
-}
-
-/// Check if the branch is against the boundary.
-///
-/// \param StartAddr start address of the fused/unfused branch.
-/// \param Size size of the fused/unfused branch.
-/// \param BoundaryAlignment alignment requirement of the branch.
-/// \returns true if the branch is against the boundary.
-static bool isAgainstBoundary(uint64_t StartAddr, uint64_t Size,
- Align BoundaryAlignment) {
- uint64_t EndAddr = StartAddr + Size;
- return (EndAddr & (BoundaryAlignment.value() - 1)) == 0;
-}
-
-/// Check if the branch needs padding.
-///
-/// \param StartAddr start address of the fused/unfused branch.
-/// \param Size size of the fused/unfused branch.
-/// \param BoundaryAlignment alignment requirement of the branch.
-/// \returns true if the branch needs padding.
-static bool needPadding(uint64_t StartAddr, uint64_t Size,
- Align BoundaryAlignment) {
- return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) ||
- isAgainstBoundary(StartAddr, Size, BoundaryAlignment);
-}
-
bool MCAssembler::relaxBoundaryAlign(MCAsmLayout &Layout,
MCBoundaryAlignFragment &BF) {
// BoundaryAlignFragment that doesn't need to align any fragment should not be
diff --git a/llvm/lib/MC/MCFragment.cpp b/llvm/lib/MC/MCFragment.cpp
index 4e6459c5d6e459f3..5a143a439ba97779 100644
--- a/llvm/lib/MC/MCFragment.cpp
+++ b/llvm/lib/MC/MCFragment.cpp
@@ -274,6 +274,9 @@ void MCFragment::destroy() {
case FT_Align:
delete cast<MCAlignFragment>(this);
return;
+ case FT_NeverAlign:
+ delete cast<MCNeverAlignFragment>(this);
+ return;
case FT_Data:
delete cast<MCDataFragment>(this);
return;
@@ -342,6 +345,9 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
OS << "<";
switch (getKind()) {
case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
+ case MCFragment::FT_NeverAlign:
+ OS << "MCNeverAlignFragment";
+ break;
case MCFragment::FT_Data: OS << "MCDataFragment"; break;
case MCFragment::FT_CompactEncodedInst:
OS << "MCCompactEncodedInstFragment"; break;
@@ -381,6 +387,12 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
<< " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
break;
}
+ case MCFragment::FT_NeverAlign: {
+ const MCNeverAlignFragment *NAF = cast<MCNeverAlignFragment>(this);
+ OS << "\n ";
+ OS << " Alignment:" << NAF->getAlignment() << ">";
+ break;
+ }
case MCFragment::FT_Data: {
const auto *DF = cast<MCDataFragment>(this);
OS << "\n ";
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index 3cf7b4359cabab6a..3f4fb6ca9f0ae247 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -659,6 +659,11 @@ void MCObjectStreamer::emitCodeAlignment(Align Alignment,
cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true, STI);
}
+void MCObjectStreamer::emitNeverAlignCodeAtEnd(unsigned ByteAlignment,
+ const MCSubtargetInfo &STI) {
+ insert(new MCNeverAlignFragment(ByteAlignment, STI));
+}
+
void MCObjectStreamer::emitValueToOffset(const MCExpr *Offset,
unsigned char Value,
SMLoc Loc) {
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index 2371cb2384414b9c..008852afa39cbe64 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -1237,6 +1237,8 @@ void MCStreamer::emitValueToAlignment(Align Alignment, int64_t Value,
unsigned MaxBytesToEmit) {}
void MCStreamer::emitCodeAlignment(Align Alignment, const MCSubtargetInfo *STI,
unsigned MaxBytesToEmit) {}
+void MCStreamer::emitNeverAlignCodeAtEnd(unsigned ByteAlignment,
+ const MCSubtargetInfo &STI) {}
void MCStreamer::emitValueToOffset(const MCExpr *Offset, unsigned char Value,
SMLoc Loc) {}
void MCStreamer::emitBundleAlignMode(Align Alignment) {}
diff --git a/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp b/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
index 19b4ea474f5284b2..414a6a9e2daba6dc 100644
--- a/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ b/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -1152,6 +1152,7 @@ class X86AsmParser : public MCTargetAsmParser {
bool parseDirectiveArch();
bool parseDirectiveNops(SMLoc L);
bool parseDirectiveEven(SMLoc L);
+ bool parseDirectiveAvoidEndAlign(SMLoc L);
bool ParseDirectiveCode(StringRef IDVal, SMLoc L);
/// CodeView FPO data directives.
@@ -4493,6 +4494,8 @@ bool X86AsmParser::ParseDirective(AsmToken DirectiveID) {
return false;
} else if (IDVal == ".nops")
return parseDirectiveNops(DirectiveID.getLoc());
+ else if (IDVal == ".avoid_end_align")
+ return parseDirectiveAvoidEndAlign(DirectiveID.getLoc());
else if (IDVal == ".even")
return parseDirectiveEven(DirectiveID.getLoc());
else if (IDVal == ".cv_fpo_proc")
@@ -4587,6 +4590,27 @@ bool X86AsmParser::parseDirectiveEven(SMLoc L) {
return false;
}
+/// Directive for NeverAlign fragment testing, not for general usage!
+/// parseDirectiveAvoidEndAlign
+/// ::= .avoid_end_align alignment
+bool X86AsmParser::parseDirectiveAvoidEndAlign(SMLoc L) {
+ int64_t Alignment = 0;
+ SMLoc AlignmentLoc;
+ AlignmentLoc = getTok().getLoc();
+ if (getParser().checkForValidSection() ||
+ getParser().parseAbsoluteExpression(Alignment))
+ return true;
+
+ if (getParser().parseEOL("unexpected token in directive"))
+ return true;
+
+ if (Alignment <= 0)
+ return Error(AlignmentLoc, "expected a positive alignment");
+
+ getParser().getStreamer().emitNeverAlignCodeAtEnd(Alignment, getSTI());
+ return false;
+}
+
/// ParseDirectiveCode
/// ::= .code16 | .code32 | .code64
bool X86AsmParser::ParseDirectiveCode(StringRef IDVal, SMLoc L) {
diff --git a/llvm/test/MC/X86/directive-avoid_end_align.s b/llvm/test/MC/X86/directive-avoid_end_align.s
new file mode 100644
index 0000000000000000..1d748401edc12ed1
--- /dev/null
+++ b/llvm/test/MC/X86/directive-avoid_end_align.s
@@ -0,0 +1,208 @@
+# RUN: llvm-mc -triple=x86_64 -filetype=obj %s | llvm-objdump --no-show-raw-insn -d - | FileCheck %s
+# RUN: not llvm-mc -triple=x86_64 --defsym ERR=1 %s -o /dev/null 2>&1 | FileCheck %s --check-prefix=ERR
+
+# avoid_end_align has no effect since test doesn't end at alignment boundary:
+.avoid_end_align 64
+# CHECK-NOT: nop
+ testl %eax, %eax
+# CHECK: testl %eax, %eax
+ je .LBB0
+
+.fill 58, 1, 0x00
+# NeverAlign followed by MCDataFragment:
+# avoid_end_align inserts nop because `test` would end at alignment boundary:
+.avoid_end_align 64
+# CHECK: 3e: nop
+ testl %eax, %eax
+# CHECK-NEXT: 3f: testl %eax, %eax
+ je .LBB0
+# CHECK-NEXT: 41: je
+.LBB0:
+ retq
+
+.p2align 6
+.L0:
+.nops 57
+ int3
+# NeverAlign followed by RelaxableFragment:
+.avoid_end_align 64
+# CHECK: ba: nop
+ cmpl $(.L1-.L0), %eax
+# CHECK-NEXT: bb: cmpl
+ je .L0
+# CHECK-NEXT: c1: je
+.nops 65
+.L1:
+
+###############################################################################
+# Experiment A:
+# Check that NeverAlign doesn't introduce infinite loops in layout.
+# Control:
+# 1. NeverAlign fragment is not added,
+# 2. Short formats of cmp and jcc are used (3 and 2 bytes respectively),
+# 3. cmp and jcc are placed such that to be split by 64B alignment boundary.
+# 4. jcc would be relaxed to a longer format if at least one byte is added
+# between .L10 and je itself, e.g. by adding a NeverAlign padding byte,
+# or relaxing cmp instruction.
+# 5. cmp would be relaxed to a longer format if at least one byte is added
+# between .L11 and .L12, e.g. due to relaxing jcc instruction.
+.p2align 6
+# CHECK: 140: int3
+.fill 2, 1, 0xcc
+.L10:
+.nops 122
+ int3
+# CHECK: 1bc: int3
+# no avoid_end_align here
+# CHECK-NOT: nop
+ cmp $(.L12-.L11), %eax
+# CHECK: 1bd: cmpl
+.L11:
+ je .L10
+# CHECK-NEXT: 1c0: je
+.nops 125
+.L12:
+
+# Experiment:
+# Same setup as control, except NeverAlign fragment is added before cmp.
+# Expected effect:
+# 1. NeverAlign pads cmp+jcc by one byte since cmp and jcc are split by a 64B
+# alignment boundary,
+# 2. This extra byte forces jcc relaxation to a longer format (Control rule #4),
+# 3. This results in an cmp relaxation (Control rule #5),
+# 4. Which in turn makes NeverAlign fragment unnecessary as cmp and jcc
+# are no longer split by an alignment boundary (cmp crosses the boundary).
+# 5. NeverAlign padding is removed.
+# 6. cmp and jcc instruction remain in relaxed form.
+# 7. Relaxation converges, layout succeeds.
+.p2align 6
+# CHECK: 240: int3
+.fill 2, 1, 0xcc
+.L20:
+.nops 122
+ int3
+# CHECK: 2bc: int3
+.avoid_end_align 64
+# CHECK-NOT: nop
+ cmp $(.L22-.L21), %eax
+# CHECK-NEXT: 2bd: cmpl
+.L21:
+ je .L20
+# CHECK-NEXT: 2c3: je
+.nops 125
+.L22:
+
+###############################################################################
+# Experiment B: similar to exp A, but we check that once NeverAlign padding is
+# removed from the layout (exp A, experiment step 5), the increased distance
+# between the symbols L33 and L34 triggers the relaxation of instruction at
+# label L32.
+#
+# Control 1: using a one-byte instruction at L33 (site of NeverAlign) leads to
+# steps 2-3 of exp A, experiment:
+# 2. This extra byte forces jcc relaxation to a longer format (Control rule #4),
+# 3. This results in an cmp relaxation (Control rule #5),
+# => short cmp under L32
+.p2align 6
+# CHECK: 380: int3
+.fill 2, 1, 0xcc
+.L30:
+.nops 122
+ int3
+# CHECK: 3fc: int3
+ hlt
+#.avoid_end_align 64
+.L33:
+ cmp $(.L32-.L31), %eax
+# CHECK: 3fe: cmpl
+.L31:
+ je .L30
+# CHECK-NEXT: 404: je
+.nops 114
+.p2align 1
+ int3
+ int3
+# CHECK: 47c: int3
+.L34:
+.nops 9
+.L32:
+ cmp $(.L33-.L34), %eax
+# CHECK: 487: cmp
+# note that the size of cmp is 48a-487 == 3 bytes (distance is exactly -128)
+ int3
+# CHECK-NEXT: 48a: int3
+
+# Control 2: leaving out a byte at L43 (site of NeverAlign), plus
+# relaxed jcc and cmp leads to a relaxed cmp under L42 (-129 as cmp's immediate)
+.p2align 6
+# CHECK: 4c0: int3
+.fill 2, 1, 0xcc
+.L40:
+.nops 122
+ int3
+# CHECK: 53c: int3
+# int3
+#.avoid_end_align 64
+.L43:
+ cmp $(.L42-.L41+0x100), %eax
+# CHECK: 53d: cmpl
+.L41:
+ je .L40+0x100
+# CHECK-NEXT: 543: je
+.nops 114
+.p2align 1
+ int3
+ int3
+# CHECK: 5bc: int3
+.L44:
+.nops 9
+.L42:
+ cmp $(.L43-.L44), %eax
+# CHECK: 5c7: cmp
+# note that the size of cmp is 5cd-5c7 == 6 bytes (distance is exactly -129)
+ int3
+# CHECK-NEXT: 5cd: int3
+
+# Experiment
+# Checking if removing NeverAlign padding at L53 as a result of alignment and
+# relaxation of cmp and jcc following it (see exp A), thus reproducing the case
+# in Control 2 (getting a relaxed cmp under L52), is handled correctly.
+.p2align 6
+# CHECK: 600: int3
+.fill 2, 1, 0xcc
+.L50:
+.nops 122
+ int3
+# CHECK: 67c: int3
+.avoid_end_align 64
+.L53:
+# CHECK-NOT: nop
+ cmp $(.L52-.L51), %eax
+# CHECK-NEXT: 67d: cmpl
+.L51:
+ je .L50
+# CHECK-NEXT: 683: je
+.nops 114
+.p2align 1
+ int3
+ int3
+# CHECK: 6fc: int3
+.L54:
+.nops 9
+.L52:
+ cmp $(.L53-.L54), %eax
+# CHECK: 707: cmp
+# note that the size of cmp is 70d-707 == 6 bytes (distance is exactly -129)
+ int3
+# CHECK-NEXT: 70d: int3
+
+.ifdef ERR
+# ERR: {{.*}}.s:[[#@LINE+1]]:17: error: unknown token in expression
+.avoid_end_align
+# ERR: {{.*}}.s:[[#@LINE+1]]:18: error: expected absolute expression
+.avoid_end_align x
+# ERR: {{.*}}.s:[[#@LINE+1]]:18: error: expected a positive alignment
+.avoid_end_align 0
+# ERR: {{.*}}.s:[[#@LINE+1]]:20: error: unexpected token in directive
+.avoid_end_align 64, 0
+.endif
>From 98e1f4c3b15f677e5dbfa85dace75e4c092bb99f Mon Sep 17 00:00:00 2001
From: Shatian Wang <shatian at meta.com>
Date: Thu, 2 Nov 2023 12:26:49 -0700
Subject: [PATCH 3/3] [BOLT] Extend calculateEmittedSize for Block Size
Calculation
Summary:
This commit modifies BinaryContext::calculateEmittedSize to update the
BinaryBasicBlock::OutputAddressRange for each basic block in the input
BF. The modification is done in place, where BB.OutputAddressRange.second
less BB.OutputAddressRange.first now gives the emitted size of the basic
block.
Test Plan:
Reviewers:
Subscribers:
Tasks:
Tags:
Differential Revision: https://phabricator.intern.facebook.com/D51520268
---
bolt/include/bolt/Core/BinaryContext.h | 3 +++
bolt/lib/Core/BinaryContext.cpp | 35 +++++++++++++++++++++-----
2 files changed, 32 insertions(+), 6 deletions(-)
diff --git a/bolt/include/bolt/Core/BinaryContext.h b/bolt/include/bolt/Core/BinaryContext.h
index a4e84cb93c093dc2..258063e8584bb5d2 100644
--- a/bolt/include/bolt/Core/BinaryContext.h
+++ b/bolt/include/bolt/Core/BinaryContext.h
@@ -1230,6 +1230,9 @@ class BinaryContext {
///
/// Return the pair where the first size is for the main part, and the second
/// size is for the cold one.
+ /// Modify BinaryBasicBlock::OutputAddressRange for each basic block in the
+ /// function in place so that BB.OutputAddressRange.second less
+ /// BB.OutputAddressRange.first gives the emitted size of BB.
std::pair<size_t, size_t> calculateEmittedSize(BinaryFunction &BF,
bool FixBranches = true);
diff --git a/bolt/lib/Core/BinaryContext.cpp b/bolt/lib/Core/BinaryContext.cpp
index cd70bdb7a4228d0b..af33398c9a9f2736 100644
--- a/bolt/lib/Core/BinaryContext.cpp
+++ b/bolt/lib/Core/BinaryContext.cpp
@@ -2322,14 +2322,37 @@ BinaryContext::calculateEmittedSize(BinaryFunction &BF, bool FixBranches) {
MCAsmLayout Layout(Assembler);
Assembler.layout(Layout);
+ // Obtain fragment sizes.
+ std::vector<uint64_t> FragmentSizes;
+ // Main fragment size.
const uint64_t HotSize =
Layout.getSymbolOffset(*EndLabel) - Layout.getSymbolOffset(*StartLabel);
- const uint64_t ColdSize =
- std::accumulate(SplitLabels.begin(), SplitLabels.end(), 0ULL,
- [&](const uint64_t Accu, const LabelRange &Labels) {
- return Accu + Layout.getSymbolOffset(*Labels.second) -
- Layout.getSymbolOffset(*Labels.first);
- });
+ FragmentSizes.push_back(HotSize);
+ // Split fragment sizes.
+ uint64_t ColdSize = 0;
+ for (const auto &Labels : SplitLabels) {
+ uint64_t Size = Layout.getSymbolOffset(*Labels.second) -
+ Layout.getSymbolOffset(*Labels.first);
+ FragmentSizes.push_back(Size);
+ ColdSize += Size;
+ }
+
+ // Populate new start and end offsets of each basic block.
+ BinaryBasicBlock *PrevBB = nullptr;
+ uint64_t FragmentIndex = 0;
+ for (FunctionFragment &FF : BF.getLayout().fragments()) {
+ for (BinaryBasicBlock *BB : FF) {
+ const uint64_t BBStartOffset = Layout.getSymbolOffset(*(BB->getLabel()));
+ BB->setOutputStartAddress(BBStartOffset);
+ if (PrevBB)
+ PrevBB->setOutputEndAddress(BBStartOffset);
+ PrevBB = BB;
+ }
+ if (PrevBB)
+ PrevBB->setOutputEndAddress(FragmentSizes[FragmentIndex]);
+ FragmentIndex++;
+ PrevBB = nullptr;
+ }
// Clean-up the effect of the code emission.
for (const MCSymbol &Symbol : Assembler.symbols()) {
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