Add support for code model selection #4318
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lib/std/builtin.zig
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| pub const CodeModel = enum { | ||
| Default, | ||
| Tiny, | ||
| Small, | ||
| Kernel, | ||
| Medium, | ||
| Large, | ||
| }; |
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New enums should follow #2101. This will be nice because you can use @tagName above instead of the switch.
lib/std/build.zig
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| @@ -1149,6 +1149,7 @@ pub const LibExeObjStep = struct { | |||
| name_prefix: []const u8, | |||
| filter: ?[]const u8, | |||
| single_threaded: bool, | |||
| code_model: ?builtin.CodeModel, | |||
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I suggest:
| code_model: ?builtin.CodeModel, | |
| code_model: builtin.CodeModel = CodeModel.default, |
and then the code below should omit the -code-model parameter when the value is default.
src/all_types.hpp
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| LLVMCodeModel code_model; | ||
| CodeModel want_code_model; |
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I think we only need 1 field here:
CodeModel code_model;codegen_create can default this to CodeModelDefault. main.cpp can override it.
The code that generates builtin.zig can switch on the CodeModel (not the LLVM one).
detect_code_model can be renamed to to_llvm_code_model, and only called once, for createTargetMachine.
The want_* mechanisms don't apply to this parameter, since it has a default and there is no logic in the "detect" phase.
| /// This data structure is used by the Zig language code generation and | ||
| /// therefore must be kept in sync with the compiler implementation. | ||
| pub const CodeModel = enum { |
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Can you add your handy explanation to the doc comments?
/// The code model puts constraints on the location of symbols and the size of code and data.
/// The selection of a code model is a trade off on speed and restrictions that needs to be selected on a per application basis to meet its requirements.
/// A slightly more detailed explanation can be found in (for example) the [System V Application Binary Interface (x86_64)](https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-1.0.pdf) 3.5.1.
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Thanks! |
This pull request allows the user to select the code model that is targeted through the
-code-modelcompiler flag or theLibExeObjStep.code_modelfield.It is exposed through
builtin.code_model.Explanation:
In short the code model puts constraints on the location of symbols and the size of code and data.
The selection of a code model is a trade off on speed and restrictions that needs to be selected on a per application basis to meet its requirements.
A slightly more detailed explanation can be found in (for example) the System V Application Binary Interface (x86_64) 3.5.1.
Example:
An application compiled with the default amd64 code model (small) cannot be linked into negative address space because of the restrictions that it imposes.
Example for the linker error that would occur:
The same code targeting the large or kernel code models would be allowed to link.