Fix lowering and optimization of 64-bit absolute addresses

x86-64 does not support 64-bit immediates as absolute memory addresses.
They have to be stored in a register, which can then be used as [base].

Previously we addressed this at the SubzeroReactor level by emitting a
Bitcast from an Ice::Operand to an Ice::Variable, for which Subzero
already supported 64-bit constants as input.

This change implements X86OperandMem creation from a 64-bit constant
operand by letting legalize() move it into a GPR and using it as the
memory operand's base register.

A Reactor unit test is added to exercise this.

Another issue was that doLoadOpt() assumed all load instructions are
candidates for fusing into a subsequent instruction which takes the
result of the load. This isn't true when for 64-bit constant addresses
an instruction to copy it into a register is inserted.

For now this case is simply skipped. A future optimization could adjust
the iterators properly so the load from [base] can be fused with the
next instruction.

Lastly, it is possible for a 64-bit constant to fit within a 32-bit
immediate, in which case legalize() by default does not perform the copy
into a GPR (note this is to allow moves and calls with 64-bit
immediates, where they are legal), and simply returns the 64-bit
constant. So we must not allow legalization to an immediate in this
case. Note that while we could replace it with a 32-bit constant, it's
rare for absolute addresses to fit in this range, and it would be
non-deterministic which path is taken, so for consistency we don't
perform this optimization.

Bug: b/148272103
Change-Id: I5fcfa971dc93f2307202ee11619e84c65fe46188
Tested-by: Nicolas Capens <>
Presubmit-Ready: Nicolas Capens <>
Reviewed-by: Antonio Maiorano <>
4 files changed
tree: eb4b9074275cb79ca91ed2696f6b16b193a567b2
  1. .clang-format
  2. .dir-locals.el
  3. .gitignore
  4. .gitmodules
  5. .vscode/
  6. AUTHORS.txt
  7. Android.bp
  9. CMakeLists.txt
  10. CMakeSettings.json
  14. LICENSE.txt
  15. OWNERS
  17. build/
  18. build_overrides/
  19. codereview.settings
  20. docs/
  21. extensions/
  22. include/
  23. infra/
  24. src/
  25. tests/
  26. third_party/
  27. tools/




SwiftShader is a high-performance CPU-based implementation of the Vulkan graphics API12. Its goal is to provide hardware independence for advanced 3D graphics.

NOTE: SwiftShader's OpenGL ES frontend is no longer supported, and will eventually be removed. Read more about our recommendation to use ANGLE on top of SwiftShader Vulkan here.


SwiftShader libraries can be built for Windows, Linux, and macOS.
Android and Chrome (OS) build environments are also supported.

  • CMake
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On Windows, most applications can be made to use SwiftShader's DLLs by placing them in the same folder as the executable. On Linux, the LD_LIBRARY_PATH environment variable or -rpath linker option can be used to direct applications to search for shared libraries in the indicated directory first.

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See docs/ for details.

Third-Party Dependencies

The third_party directory contains projects which originated outside of SwiftShader:

subzero contains a fork of the Subzero project. It originates from Google Chrome‘s (Portable) Native Client project. The fork was made using git-subtree to include all of Subzero’s history.

llvm-subzero contains a minimized set of LLVM dependencies of the Subzero project.

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See docs/


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