[clang] fb6c10d - [MC] Emit a jump table size section (#101962)
via cfe-commits
cfe-commits at lists.llvm.org
Fri Sep 6 05:41:40 PDT 2024
Author: Nabeel Omer
Date: 2024-09-06T13:41:36+01:00
New Revision: fb6c10da1f6cb4eb9556548d51dafe97d953ba58
URL: https://github.com/llvm/llvm-project/commit/fb6c10da1f6cb4eb9556548d51dafe97d953ba58
DIFF: https://github.com/llvm/llvm-project/commit/fb6c10da1f6cb4eb9556548d51dafe97d953ba58.diff
LOG: [MC] Emit a jump table size section (#101962)
This patch will make LLVM emit a new section .llvm_jump_table_sizes
containing tuples of (jump table address, entry count) in object files.
This section is useful for tools that need to statically reconstruct the
control flow of executables.
At the moment this is only enabled by default for the PS5 target.
Added:
llvm/test/CodeGen/X86/jump-table-size-section.ll
Modified:
clang/lib/Driver/ToolChains/PS4CPU.cpp
clang/test/Driver/ps4-ps5-toolchain.c
llvm/docs/Extensions.rst
llvm/include/llvm/BinaryFormat/ELF.h
llvm/include/llvm/CodeGen/AsmPrinter.h
llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
llvm/lib/MC/MCParser/ELFAsmParser.cpp
llvm/lib/MC/MCSectionELF.cpp
llvm/lib/Object/ELF.cpp
Removed:
################################################################################
diff --git a/clang/lib/Driver/ToolChains/PS4CPU.cpp b/clang/lib/Driver/ToolChains/PS4CPU.cpp
index 54ec59e6398f85..48d824171303cc 100644
--- a/clang/lib/Driver/ToolChains/PS4CPU.cpp
+++ b/clang/lib/Driver/ToolChains/PS4CPU.cpp
@@ -272,6 +272,8 @@ void tools::PS5cpu::Linker::ConstructJob(Compilation &C, const JobAction &JA,
CmdArgs.push_back(D.getLTOMode() == LTOK_Thin ? "--lto=thin"
: "--lto=full");
+ AddLTOFlag("-emit-jump-table-sizes-section");
+
if (UseJMC)
AddLTOFlag("-enable-jmc-instrument");
@@ -484,6 +486,12 @@ void toolchains::PS4PS5Base::addClangTargetOptions(
else
CC1Args.push_back("-fvisibility-externs-nodllstorageclass=keep");
}
+
+ // Enable jump table sizes section for PS5.
+ if (getTriple().isPS5()) {
+ CC1Args.push_back("-mllvm");
+ CC1Args.push_back("-emit-jump-table-sizes-section");
+ }
}
// PS4 toolchain.
diff --git a/clang/test/Driver/ps4-ps5-toolchain.c b/clang/test/Driver/ps4-ps5-toolchain.c
index 444e9df24714bd..c9987c2b5758b3 100644
--- a/clang/test/Driver/ps4-ps5-toolchain.c
+++ b/clang/test/Driver/ps4-ps5-toolchain.c
@@ -11,3 +11,8 @@
// RUN: %clang %s -### -target x86_64-sie-ps5 -flto 2>&1 | FileCheck %s --check-prefix=LTO
// LTO-NOT: error:
// LTO-NOT: unable to pass LLVM bit-code
+
+// Verify that the jump table sizes section is enabled.
+// RUN: %clang %s -target x86_64-sie-ps5 -### 2>&1 | FileCheck -check-prefix=JUMPTABLESIZES %s
+// JUMPTABLESIZES: "-mllvm" "-emit-jump-table-sizes-section"
+// JUMPTABLESIZES: "-plugin-opt=-emit-jump-table-sizes-section"
diff --git a/llvm/docs/Extensions.rst b/llvm/docs/Extensions.rst
index 74ca8cb0aa6879..abc34bc3202c09 100644
--- a/llvm/docs/Extensions.rst
+++ b/llvm/docs/Extensions.rst
@@ -554,6 +554,12 @@ time. This section is generated when the compiler enables fat LTO. This section
has the ``SHF_EXCLUDE`` flag so that it is stripped from the final executable
or shared library.
+``SHT_LLVM_JT_SIZES`` Section (Jump table addresses and sizes)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+This section stores pairs of (jump table address, number of entries).
+This information is useful for tools that need to statically reconstruct
+the control flow of executables.
+
CodeView-Dependent
------------------
diff --git a/llvm/include/llvm/BinaryFormat/ELF.h b/llvm/include/llvm/BinaryFormat/ELF.h
index d61d0961d5987d..2eff87c911343f 100644
--- a/llvm/include/llvm/BinaryFormat/ELF.h
+++ b/llvm/include/llvm/BinaryFormat/ELF.h
@@ -1129,6 +1129,7 @@ enum : unsigned {
SHT_LLVM_BB_ADDR_MAP = 0x6fff4c0a, // LLVM Basic Block Address Map.
SHT_LLVM_OFFLOADING = 0x6fff4c0b, // LLVM device offloading data.
SHT_LLVM_LTO = 0x6fff4c0c, // .llvm.lto for fat LTO.
+ SHT_LLVM_JT_SIZES = 0x6fff4c0d, // LLVM jump tables sizes.
// Android's experimental support for SHT_RELR sections.
// https://android.googlesource.com/platform/bionic/+/b7feec74547f84559a1467aca02708ff61346d2a/libc/include/elf.h#512
SHT_ANDROID_RELR = 0x6fffff00, // Relocation entries; only offsets.
diff --git a/llvm/include/llvm/CodeGen/AsmPrinter.h b/llvm/include/llvm/CodeGen/AsmPrinter.h
index 36d1b479738704..c9a88d7b1c015c 100644
--- a/llvm/include/llvm/CodeGen/AsmPrinter.h
+++ b/llvm/include/llvm/CodeGen/AsmPrinter.h
@@ -894,6 +894,10 @@ class AsmPrinter : public MachineFunctionPass {
void emitJumpTableEntry(const MachineJumpTableInfo *MJTI,
const MachineBasicBlock *MBB, unsigned uid) const;
+
+ void emitJumpTableSizesSection(const MachineJumpTableInfo *MJTI,
+ const Function &F) const;
+
void emitLLVMUsedList(const ConstantArray *InitList);
/// Emit llvm.ident metadata in an '.ident' directive.
void emitModuleIdents(Module &M);
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 88e9b9d27d3f27..db7adfd3b21e5f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -99,6 +99,7 @@
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCSymbolCOFF.h"
#include "llvm/MC/MCSymbolELF.h"
#include "llvm/MC/MCTargetOptions.h"
#include "llvm/MC/MCValue.h"
@@ -107,6 +108,7 @@
#include "llvm/Pass.h"
#include "llvm/Remarks/RemarkStreamer.h"
#include "llvm/Support/Casting.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileSystem.h"
@@ -155,6 +157,11 @@ static cl::bits<PGOMapFeaturesEnum> PgoAnalysisMapFeatures(
"Enable extended information within the SHT_LLVM_BB_ADDR_MAP that is "
"extracted from PGO related analysis."));
+static cl::opt<bool> EmitJumpTableSizesSection(
+ "emit-jump-table-sizes-section",
+ cl::desc("Emit a section containing jump table addresses and sizes"),
+ cl::Hidden, cl::init(false));
+
STATISTIC(EmittedInsts, "Number of machine instrs printed");
char AsmPrinter::ID = 0;
@@ -2786,10 +2793,62 @@ void AsmPrinter::emitJumpTableInfo() {
for (const MachineBasicBlock *MBB : JTBBs)
emitJumpTableEntry(MJTI, MBB, JTI);
}
+
+ if (EmitJumpTableSizesSection)
+ emitJumpTableSizesSection(MJTI, F);
+
if (!JTInDiffSection)
OutStreamer->emitDataRegion(MCDR_DataRegionEnd);
}
+void AsmPrinter::emitJumpTableSizesSection(const MachineJumpTableInfo *MJTI,
+ const Function &F) const {
+ const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
+
+ if (JT.empty())
+ return;
+
+ StringRef GroupName = F.hasComdat() ? F.getComdat()->getName() : "";
+ MCSection *JumpTableSizesSection = nullptr;
+ StringRef sectionName = ".llvm_jump_table_sizes";
+
+ bool isElf = TM.getTargetTriple().isOSBinFormatELF();
+ bool isCoff = TM.getTargetTriple().isOSBinFormatCOFF();
+
+ if (!isCoff && !isElf)
+ return;
+
+ if (isElf) {
+ MCSymbolELF *LinkedToSym = dyn_cast<MCSymbolELF>(CurrentFnSym);
+ int Flags = F.hasComdat() ? ELF::SHF_GROUP : 0;
+
+ JumpTableSizesSection = OutContext.getELFSection(
+ sectionName, ELF::SHT_LLVM_JT_SIZES, Flags, 0, GroupName, F.hasComdat(),
+ MCSection::NonUniqueID, LinkedToSym);
+ } else if (isCoff) {
+ if (F.hasComdat()) {
+ JumpTableSizesSection = OutContext.getCOFFSection(
+ sectionName,
+ COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ |
+ COFF::IMAGE_SCN_LNK_COMDAT | COFF::IMAGE_SCN_MEM_DISCARDABLE,
+ F.getComdat()->getName(), COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
+ } else {
+ JumpTableSizesSection = OutContext.getCOFFSection(
+ sectionName, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
+ COFF::IMAGE_SCN_MEM_READ |
+ COFF::IMAGE_SCN_MEM_DISCARDABLE);
+ }
+ }
+
+ OutStreamer->switchSection(JumpTableSizesSection);
+
+ for (unsigned JTI = 0, E = JT.size(); JTI != E; ++JTI) {
+ const std::vector<MachineBasicBlock *> &JTBBs = JT[JTI].MBBs;
+ OutStreamer->emitSymbolValue(GetJTISymbol(JTI), TM.getProgramPointerSize());
+ OutStreamer->emitIntValue(JTBBs.size(), TM.getProgramPointerSize());
+ }
+}
+
/// EmitJumpTableEntry - Emit a jump table entry for the specified MBB to the
/// current stream.
void AsmPrinter::emitJumpTableEntry(const MachineJumpTableInfo *MJTI,
diff --git a/llvm/lib/MC/MCParser/ELFAsmParser.cpp b/llvm/lib/MC/MCParser/ELFAsmParser.cpp
index e8a22d3defd6e8..c4536441665fa0 100644
--- a/llvm/lib/MC/MCParser/ELFAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/ELFAsmParser.cpp
@@ -677,6 +677,8 @@ bool ELFAsmParser::ParseSectionArguments(bool IsPush, SMLoc loc) {
Type = ELF::SHT_LLVM_OFFLOADING;
else if (TypeName == "llvm_lto")
Type = ELF::SHT_LLVM_LTO;
+ else if (TypeName == "llvm_jt_sizes")
+ Type = ELF::SHT_LLVM_JT_SIZES;
else if (TypeName.getAsInteger(0, Type))
return TokError("unknown section type");
}
diff --git a/llvm/lib/MC/MCSectionELF.cpp b/llvm/lib/MC/MCSectionELF.cpp
index 5cd6590fb626d3..25e62b70b5e2a0 100644
--- a/llvm/lib/MC/MCSectionELF.cpp
+++ b/llvm/lib/MC/MCSectionELF.cpp
@@ -172,6 +172,8 @@ void MCSectionELF::printSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
OS << "llvm_offloading";
else if (Type == ELF::SHT_LLVM_LTO)
OS << "llvm_lto";
+ else if (Type == ELF::SHT_LLVM_JT_SIZES)
+ OS << "llvm_jt_sizes";
else
OS << "0x" << Twine::utohexstr(Type);
diff --git a/llvm/lib/Object/ELF.cpp b/llvm/lib/Object/ELF.cpp
index e47a40b8715dd5..c66736fb2c9194 100644
--- a/llvm/lib/Object/ELF.cpp
+++ b/llvm/lib/Object/ELF.cpp
@@ -319,6 +319,7 @@ StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) {
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_BB_ADDR_MAP);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_OFFLOADING);
STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_LTO);
+ STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_JT_SIZES)
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES);
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH);
STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verdef);
diff --git a/llvm/test/CodeGen/X86/jump-table-size-section.ll b/llvm/test/CodeGen/X86/jump-table-size-section.ll
new file mode 100644
index 00000000000000..c0b57e96d56b02
--- /dev/null
+++ b/llvm/test/CodeGen/X86/jump-table-size-section.ll
@@ -0,0 +1,210 @@
+; RUN: llc %s -o - -mtriple x86_64-sie-ps5 -emit-jump-table-sizes-section -verify-machineinstrs --relocation-model=pic | FileCheck --check-prefix=PS5-CHECK %s
+; RUN: llc %s -o - -mtriple x86_64-sie-ps5 -verify-machineinstrs --relocation-model=pic | FileCheck --check-prefix=NOFLAG %s
+; RUN: llc %s -o - -mtriple x86_64-sie-ps5 -verify-machineinstrs --relocation-model=pic | FileCheck --check-prefix=NOTABLE %s
+
+; RUN: llc %s -o - -mtriple x86_64-unknown-linux-gnu -emit-jump-table-sizes-section -verify-machineinstrs --relocation-model=pic | FileCheck --check-prefix=ELF-CHECK %s
+; RUN: llc %s -o - -mtriple x86_64-unknown-linux-gnu -verify-machineinstrs --relocation-model=pic | FileCheck --check-prefix=NOFLAG %s
+; RUN: llc %s -o - -mtriple x86_64-unknown-linux-gnu -verify-machineinstrs --relocation-model=pic | FileCheck --check-prefix=NOTABLE %s
+
+; RUN: llc %s -o - -mtriple x86_64-pc-windows-msvc -emit-jump-table-sizes-section -verify-machineinstrs --relocation-model=pic | FileCheck --check-prefix=COFF-CHECK %s
+; RUN: llc %s -o - -mtriple x86_64-pc-windows-msvc -verify-machineinstrs --relocation-model=pic | FileCheck --check-prefix=NOFLAG %s
+; RUN: llc %s -o - -mtriple x86_64-pc-windows-msvc -verify-machineinstrs --relocation-model=pic | FileCheck --check-prefix=NOTABLE %s
+
+; This test verifies the jump table size section. Currently only enabled by default on the PS5 target.
+
+$foo1 = comdat any
+
+; Ensure proper comdat handling.
+define void @foo1(i32 %x, ptr %to) comdat {
+
+; PS5-CHECK-LABEL: foo1
+; PS5-CHECK: .section .llvm_jump_table_sizes,"G", at llvm_jt_sizes,foo1,comdat
+; PS5-CHECK-NEXT: .quad .LJTI0_0
+; PS5-CHECK-NEXT: .quad 6
+
+; ELF-CHECK-LABEL: foo1
+; ELF-CHECK: .section .llvm_jump_table_sizes,"G", at llvm_jt_sizes,foo1,comdat
+; ELF-CHECK-NEXT: .quad .LJTI0_0
+; ELF-CHECK-NEXT: .quad 6
+
+; COFF-CHECK-LABEL: foo1
+; COFF-CHECK: .section .llvm_jump_table_sizes,"drD",associative,foo1
+; COFF-CHECK-NEXT: .quad .LJTI0_0
+; COFF-CHECK-NEXT: .quad 6
+
+; NOFLAG-LABEL: foo1
+; NOFLAG-NOT: .section .llvm_jump_table_sizes
+
+entry:
+ switch i32 %x, label %default [
+ i32 0, label %bb0
+ i32 1, label %bb1
+ i32 2, label %bb2
+ i32 3, label %bb3
+ i32 4, label %bb4
+ i32 5, label %bb4
+ ]
+bb0:
+ store i32 0, ptr %to
+ br label %exit
+bb1:
+ store i32 1, ptr %to
+ br label %exit
+bb2:
+ store i32 2, ptr %to
+ br label %exit
+bb3:
+ store i32 3, ptr %to
+ br label %exit
+bb4:
+ store i32 4, ptr %to
+ br label %exit
+exit:
+ ret void
+default:
+ unreachable
+}
+
+define void @foo2(i32 %x, ptr %to) {
+
+; PS5-CHECK-LABEL: foo2
+; PS5-CHECK: .section .llvm_jump_table_sizes,"", at llvm_jt_sizes
+; PS5-CHECK-NEXT: .quad .LJTI1_0
+; PS5-CHECK-NEXT: .quad 5
+
+; ELF-CHECK-LABEL: foo2
+; ELF-CHECK: .section .llvm_jump_table_sizes,"", at llvm_jt_sizes
+; ELF-CHECK-NEXT: .quad .LJTI1_0
+; ELF-CHECK-NEXT: .quad 5
+
+; COFF-CHECK-LABEL: foo2
+; COFF-CHECK: .section .llvm_jump_table_sizes,"drD"
+; COFF-CHECK-NEXT: .quad .LJTI1_0
+; COFF-CHECK-NEXT: .quad 5
+
+; NOFLAG-LABEL: foo1
+; NOFLAG-NOT: .section .llvm_jump_table_sizes
+
+entry:
+ switch i32 %x, label %default [
+ i32 0, label %bb0
+ i32 1, label %bb1
+ i32 2, label %bb2
+ i32 3, label %bb3
+ i32 4, label %bb4
+ ]
+bb0:
+ store i32 0, ptr %to
+ br label %exit
+bb1:
+ store i32 1, ptr %to
+ br label %exit
+bb2:
+ store i32 2, ptr %to
+ br label %exit
+bb3:
+ store i32 3, ptr %to
+ br label %exit
+bb4:
+ store i32 4, ptr %to
+ br label %exit
+exit:
+ ret void
+default:
+ unreachable
+}
+
+; Ensure that the section isn't produced if there is no jump table.
+
+define void @foo3(i32 %x, ptr %to) {
+
+; NOTABLE-LABEL: foo3
+; NOTABLE-NOT: .section .llvm_jump_table_sizes
+
+exit:
+ ret void
+}
+
+; Ensure we can deal with nested jump tables.
+
+define void @nested(i32 %x, i32 %y, ptr %to) {
+
+; PS5-CHECK-LABEL: nested
+; PS5-CHECK: .section .llvm_jump_table_sizes,"", at llvm_jt_sizes
+; PS5-CHECK-NEXT: .quad .LJTI3_0
+; PS5-CHECK-NEXT: .quad 5
+; PS5-CHECK-NEXT: .quad .LJTI3_1
+; PS5-CHECK-NEXT: .quad 6
+
+; ELF-CHECK-LABEL: nested
+; ELF-CHECK: .section .llvm_jump_table_sizes,"", at llvm_jt_sizes
+; ELF-CHECK-NEXT: .quad .LJTI3_0
+; ELF-CHECK-NEXT: .quad 5
+; ELF-CHECK-NEXT: .quad .LJTI3_1
+; ELF-CHECK-NEXT: .quad 6
+
+; COFF-CHECK-LABEL: nested
+; COFF-CHECK: .section .llvm_jump_table_sizes,"drD"
+; COFF-CHECK-NEXT: .quad .LJTI3_0
+; COFF-CHECK-NEXT: .quad 5
+; COFF-CHECK-NEXT: .quad .LJTI3_1
+; COFF-CHECK-NEXT: .quad 6
+
+; NOFLAG-LABEL: nested
+; NOFLAG-NOT: .section .llvm_jump_table_sizes
+
+entry:
+ switch i32 %x, label %default [
+ i32 0, label %bb0
+ i32 1, label %bb1
+ i32 2, label %bb2
+ i32 3, label %bb3
+ i32 4, label %bb4
+ ]
+bb0:
+ store i32 0, ptr %to
+ br label %exit
+bb1:
+ store i32 1, ptr %to
+ br label %exit
+bb2:
+ store i32 2, ptr %to
+ br label %exit
+bb3:
+ store i32 3, ptr %to
+ br label %exit
+bb4:
+ switch i32 %y, label %default [
+ i32 1, label %bb5
+ i32 2, label %bb6
+ i32 3, label %bb7
+ i32 4, label %bb8
+ i32 5, label %bb9
+ i32 6, label %bb10
+ ]
+ br label %exit2
+bb5:
+ store i32 4, ptr %to
+ br label %exit
+bb6:
+ store i32 4, ptr %to
+ br label %exit
+bb7:
+ store i32 4, ptr %to
+ br label %exit
+bb8:
+ store i32 4, ptr %to
+ br label %exit
+bb9:
+ store i32 4, ptr %to
+ br label %exit
+bb10:
+ store i32 4, ptr %to
+ br label %exit
+exit:
+ ret void
+exit2:
+ ret void
+default:
+ unreachable
+}
\ No newline at end of file
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