[clang] [llvm] [LFI][X86] Add X86 LFI target and system instruction rewrites (PR #189569)

Mon Jul 6 21:57:14 PDT 2026

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `bolt-aarch64-ubuntu-shared` running on `bolt-worker-aarch64` while building `clang,llvm` at step 5 "build-bolt".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/218/builds/5086

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (build-bolt) failure: build (failure)
...
192.452 [504/34/1799] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86EncodingOptimization.cpp.o
192.643 [503/34/1800] Building CXX object lib/Target/X86/TargetInfo/CMakeFiles/LLVMX86Info.dir/X86TargetInfo.cpp.o
192.796 [502/34/1801] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86MCAsmInfo.cpp.o
193.105 [501/34/1802] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86FastISel.cpp.o
193.305 [500/34/1803] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86Subtarget.cpp.o
193.356 [499/34/1804] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86SpeculativeLoadHardening.cpp.o
193.454 [498/34/1805] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86WinEHState.cpp.o
193.719 [497/34/1806] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86ELFObjectWriter.cpp.o
193.887 [496/34/1807] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86WinCOFFObjectWriter.cpp.o
193.954 [495/34/1808] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86MCLFIRewriter.cpp.o
FAILED: lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86MCLFIRewriter.cpp.o 
ccache /usr/bin/c++ -DLLVM_EXPORTS -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GLIBCXX_USE_CXX11_ABI=1 -D_GNU_SOURCE -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbot/workspace/bolt-aarch64-ubuntu-shared/build/lib/Target/X86/MCTargetDesc -I/home/buildbot/workspace/bolt-aarch64-ubuntu-shared/llvm-project/llvm/lib/Target/X86/MCTargetDesc -I/home/buildbot/workspace/bolt-aarch64-ubuntu-shared/llvm-project/llvm/lib/Target/X86 -I/home/buildbot/workspace/bolt-aarch64-ubuntu-shared/build/lib/Target/X86 -I/home/buildbot/workspace/bolt-aarch64-ubuntu-shared/build/include -I/home/buildbot/workspace/bolt-aarch64-ubuntu-shared/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-dangling-reference -Wno-redundant-move -Wno-pessimizing-move -Wno-array-bounds -Wno-stringop-overread -Wno-dangling-pointer -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -std=c++17 -fPIC -UNDEBUG -fno-exceptions -funwind-tables -fno-rtti -MD -MT lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86MCLFIRewriter.cpp.o -MF lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86MCLFIRewriter.cpp.o.d -o lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86MCLFIRewriter.cpp.o -c /home/buildbot/workspace/bolt-aarch64-ubuntu-shared/llvm-project/llvm/lib/Target/X86/MCTargetDesc/X86MCLFIRewriter.cpp
/home/buildbot/workspace/bolt-aarch64-ubuntu-shared/llvm-project/llvm/lib/Target/X86/MCTargetDesc/X86MCLFIRewriter.cpp: In function ‘bool isGR64OrNone(llvm::MCRegister)’:
/home/buildbot/workspace/bolt-aarch64-ubuntu-shared/llvm-project/llvm/lib/Target/X86/MCTargetDesc/X86MCLFIRewriter.cpp:69:10: error: ‘X86MCRegisterClasses’ was not declared in this scope
   69 |          X86MCRegisterClasses[X86::GR64RegClassID].contains(Reg);
      |          ^~~~~~~~~~~~~~~~~~~~
/home/buildbot/workspace/bolt-aarch64-ubuntu-shared/llvm-project/llvm/lib/Target/X86/MCTargetDesc/X86MCLFIRewriter.cpp: In member function ‘void llvm::X86::X86MCLFIRewriter::rewriteFSAccess(const llvm::MCInst&, llvm::MCStreamer&, const llvm::MCSubtargetInfo&)’:
/home/buildbot/workspace/bolt-aarch64-ubuntu-shared/llvm-project/llvm/lib/Target/X86/MCTargetDesc/X86MCLFIRewriter.cpp:176:9: error: ‘X86MCRegisterClasses’ was not declared in this scope
  176 |         X86MCRegisterClasses[X86::GR64RegClassID].contains(DestReg) &&
      |         ^~~~~~~~~~~~~~~~~~~~
194.354 [495/33/1809] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86WinCOFFStreamer.cpp.o
194.424 [495/32/1810] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86ISelDAGToDAG.cpp.o
194.684 [495/31/1811] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86InstCombineIntrinsic.cpp.o
194.691 [495/30/1812] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86MachObjectWriter.cpp.o
194.725 [495/29/1813] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86WinEHUnwindV3.cpp.o
194.895 [495/28/1814] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86MCCodeEmitter.cpp.o
194.973 [495/27/1815] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86AsmBackend.cpp.o
195.152 [495/26/1816] Building CXX object lib/Target/X86/Disassembler/CMakeFiles/LLVMX86Disassembler.dir/X86Disassembler.cpp.o
195.161 [495/25/1817] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86MCInstLower.cpp.o
195.538 [495/24/1818] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/GISel/X86CallLowering.cpp.o
195.942 [495/23/1819] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86WinCOFFTargetStreamer.cpp.o
196.551 [495/22/1820] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/GISel/X86RegisterBankInfo.cpp.o
197.017 [495/21/1821] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/GISel/X86LegalizerInfo.cpp.o
197.919 [495/20/1822] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86InstrInfo.cpp.o
198.322 [495/19/1823] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86TargetMachine.cpp.o
199.318 [495/18/1824] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64GlobalISelUtils.cpp.o
200.784 [495/17/1825] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/GISel/X86PostLegalizerCombiner.cpp.o
200.836 [495/16/1826] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/GISel/X86InstructionSelector.cpp.o
200.980 [495/15/1827] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/GISel/X86PreLegalizerCombiner.cpp.o
201.316 [495/14/1828] Building CXX object lib/Target/X86/MCTargetDesc/CMakeFiles/LLVMX86Desc.dir/X86MCTargetDesc.cpp.o
202.857 [495/13/1829] Building CXX object lib/Target/X86/AsmParser/CMakeFiles/LLVMX86AsmParser.dir/X86AsmParser.cpp.o
203.703 [495/12/1830] Building CXX object lib/Target/X86/CMakeFiles/LLVMX86CodeGen.dir/X86TargetTransformInfo.cpp.o
203.986 [495/11/1831] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64PostSelectOptimize.cpp.o
205.380 [495/10/1832] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64RegisterBankInfo.cpp.o
205.385 [495/9/1833] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64CallLowering.cpp.o
208.630 [495/8/1834] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64LegalizerInfo.cpp.o
208.654 [495/7/1835] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64O0PreLegalizerCombiner.cpp.o
209.431 [495/6/1836] Building CXX object lib/Target/AArch64/CMakeFiles/LLVMAArch64CodeGen.dir/GISel/AArch64PostLegalizerLowering.cpp.o
209.799 [495/5/1837] Building CXX object lib/Transforms/Vectorize/CMakeFiles/LLVMVectorize.dir/SLPVectorizer.cpp.o

```

</details>

https://github.com/llvm/llvm-project/pull/189569