328 lines
11 KiB
Rust
328 lines
11 KiB
Rust
use crate::cdsl::settings::{SettingGroup, SettingGroupBuilder};
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pub(crate) fn define() -> SettingGroup {
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let mut settings = SettingGroupBuilder::new("shared");
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settings.add_enum(
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"regalloc",
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"Register allocator to use with the MachInst backend.",
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r#"
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This selects the register allocator as an option among those offered by the `regalloc.rs`
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crate. Please report register allocation bugs to the maintainers of this crate whenever
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possible.
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Note: this only applies to target that use the MachInst backend. As of 2020-04-17, this
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means the x86_64 backend doesn't use this yet.
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Possible values:
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- `backtracking` is a greedy, backtracking register allocator as implemented in
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Spidermonkey's optimizing tier IonMonkey. It may take more time to allocate registers, but
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it should generate better code in general, resulting in better throughput of generated
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code.
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- `backtracking_checked` is the backtracking allocator with additional self checks that may
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take some time to run, and thus these checks are disabled by default.
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- `experimental_linear_scan` is an experimental linear scan allocator. It may take less
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time to allocate registers, but generated code's quality may be inferior. As of
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2020-04-17, it is still experimental and it should not be used in production settings.
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- `experimental_linear_scan_checked` is the linear scan allocator with additional self
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checks that may take some time to run, and thus these checks are disabled by default.
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"#,
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vec![
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"backtracking",
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"backtracking_checked",
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"experimental_linear_scan",
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"experimental_linear_scan_checked",
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],
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);
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settings.add_enum(
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"opt_level",
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"Optimization level for generated code.",
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r#"
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Supported levels:
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- `none`: Minimise compile time by disabling most optimizations.
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- `speed`: Generate the fastest possible code
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- `speed_and_size`: like "speed", but also perform transformations aimed at reducing code size.
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"#,
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vec!["none", "speed", "speed_and_size"],
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);
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settings.add_bool(
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"enable_verifier",
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"Run the Cranelift IR verifier at strategic times during compilation.",
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r#"
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This makes compilation slower but catches many bugs. The verifier is always enabled by
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default, which is useful during development.
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"#,
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true,
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);
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// Note that Cranelift doesn't currently need an is_pie flag, because PIE is
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// just PIC where symbols can't be pre-empted, which can be expressed with the
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// `colocated` flag on external functions and global values.
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settings.add_bool(
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"is_pic",
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"Enable Position-Independent Code generation.",
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"",
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false,
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);
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settings.add_bool(
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"use_colocated_libcalls",
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"Use colocated libcalls.",
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r#"
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Generate code that assumes that libcalls can be declared "colocated",
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meaning they will be defined along with the current function, such that
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they can use more efficient addressing.
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"#,
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false,
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);
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settings.add_bool(
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"avoid_div_traps",
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"Generate explicit checks around native division instructions to avoid their trapping.",
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r#"
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This is primarily used by SpiderMonkey which doesn't install a signal
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handler for SIGFPE, but expects a SIGILL trap for division by zero.
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On ISAs like ARM where the native division instructions don't trap,
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this setting has no effect - explicit checks are always inserted.
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"#,
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false,
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);
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settings.add_bool(
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"enable_float",
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"Enable the use of floating-point instructions.",
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r#"
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Disabling use of floating-point instructions is not yet implemented.
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"#,
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true,
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);
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settings.add_bool(
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"enable_nan_canonicalization",
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"Enable NaN canonicalization.",
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r#"
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This replaces NaNs with a single canonical value, for users requiring
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entirely deterministic WebAssembly computation. This is not required
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by the WebAssembly spec, so it is not enabled by default.
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"#,
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false,
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);
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settings.add_bool(
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"enable_pinned_reg",
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"Enable the use of the pinned register.",
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r#"
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This register is excluded from register allocation, and is completely under the control of
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the end-user. It is possible to read it via the get_pinned_reg instruction, and to set it
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with the set_pinned_reg instruction.
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"#,
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false,
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);
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settings.add_bool(
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"use_pinned_reg_as_heap_base",
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"Use the pinned register as the heap base.",
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r#"
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Enabling this requires the enable_pinned_reg setting to be set to true. It enables a custom
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legalization of the `heap_addr` instruction so it will use the pinned register as the heap
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base, instead of fetching it from a global value.
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Warning! Enabling this means that the pinned register *must* be maintained to contain the
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heap base address at all times, during the lifetime of a function. Using the pinned
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register for other purposes when this is set is very likely to cause crashes.
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"#,
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false,
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);
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settings.add_bool(
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"enable_simd",
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"Enable the use of SIMD instructions.",
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"",
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false,
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);
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settings.add_bool(
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"enable_atomics",
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"Enable the use of atomic instructions",
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"",
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true,
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);
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settings.add_bool(
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"enable_safepoints",
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"Enable safepoint instruction insertions.",
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r#"
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This will allow the emit_stack_maps() function to insert the safepoint
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instruction on top of calls and interrupt traps in order to display the
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live reference values at that point in the program.
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"#,
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false,
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);
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settings.add_enum(
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"tls_model",
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"Defines the model used to perform TLS accesses.",
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"",
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vec!["none", "elf_gd", "macho", "coff"],
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);
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// Settings specific to the `baldrdash` calling convention.
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settings.add_enum(
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"libcall_call_conv",
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"Defines the calling convention to use for LibCalls call expansion.",
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r#"
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This may be different from the ISA default calling convention.
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The default value is to use the same calling convention as the ISA
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default calling convention.
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This list should be kept in sync with the list of calling
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conventions available in isa/call_conv.rs.
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"#,
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vec![
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"isa_default",
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"fast",
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"cold",
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"system_v",
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"windows_fastcall",
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"apple_aarch64",
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"baldrdash_system_v",
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"baldrdash_windows",
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"baldrdash_2020",
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"probestack",
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],
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);
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settings.add_num(
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"baldrdash_prologue_words",
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"Number of pointer-sized words pushed by the baldrdash prologue.",
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r#"
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Functions with the `baldrdash` calling convention don't generate their
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own prologue and epilogue. They depend on externally generated code
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that pushes a fixed number of words in the prologue and restores them
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in the epilogue.
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This setting configures the number of pointer-sized words pushed on the
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stack when the Cranelift-generated code is entered. This includes the
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pushed return address on x86.
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"#,
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0,
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);
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settings.add_bool(
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"enable_llvm_abi_extensions",
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"Enable various ABI extensions defined by LLVM's behavior.",
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r#"
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In some cases, LLVM's implementation of an ABI (calling convention)
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goes beyond a standard and supports additional argument types or
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behavior. This option instructs Cranelift codegen to follow LLVM's
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behavior where applicable.
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Currently, this applies only to Windows Fastcall on x86-64, and
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allows an `i128` argument to be spread across two 64-bit integer
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registers. The Fastcall implementation otherwise does not support
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`i128` arguments, and will panic if they are present and this
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option is not set.
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"#,
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false,
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);
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settings.add_bool(
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"unwind_info",
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"Generate unwind information.",
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r#"
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This increases metadata size and compile time, but allows for the
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debugger to trace frames, is needed for GC tracing that relies on
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libunwind (such as in Wasmtime), and is unconditionally needed on
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certain platforms (such as Windows) that must always be able to unwind.
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"#,
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true,
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);
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settings.add_bool(
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"machine_code_cfg_info",
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"Generate CFG metadata for machine code.",
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r#"
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This increases metadata size and compile time, but allows for the
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embedder to more easily post-process or analyze the generated
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machine code. It provides code offsets for the start of each
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basic block in the generated machine code, and a list of CFG
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edges (with blocks identified by start offsets) between them.
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This is useful for, e.g., machine-code analyses that verify certain
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properties of the generated code.
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"#,
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false,
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);
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// BaldrMonkey requires that not-yet-relocated function addresses be encoded
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// as all-ones bitpatterns.
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settings.add_bool(
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"emit_all_ones_funcaddrs",
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"Emit not-yet-relocated function addresses as all-ones bit patterns.",
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"",
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false,
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);
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// Stack probing options.
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settings.add_bool(
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"enable_probestack",
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"Enable the use of stack probes for supported calling conventions.",
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"",
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true,
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);
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settings.add_bool(
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"probestack_func_adjusts_sp",
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"Enable if the stack probe adjusts the stack pointer.",
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"",
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false,
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);
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settings.add_num(
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"probestack_size_log2",
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"The log2 of the size of the stack guard region.",
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r#"
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Stack frames larger than this size will have stack overflow checked
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by calling the probestack function.
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The default is 12, which translates to a size of 4096.
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"#,
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12,
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);
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// Jump table options.
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settings.add_bool(
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"enable_jump_tables",
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"Enable the use of jump tables in generated machine code.",
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"",
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true,
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);
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// Spectre options.
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settings.add_bool(
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"enable_heap_access_spectre_mitigation",
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"Enable Spectre mitigation on heap bounds checks.",
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r#"
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This is a no-op for any heap that needs no bounds checks; e.g.,
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if the limit is static and the guard region is large enough that
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the index cannot reach past it.
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This option is enabled by default because it is highly
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recommended for secure sandboxing. The embedder should consider
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the security implications carefully before disabling this option.
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"#,
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true,
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);
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settings.build()
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}
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