170 lines
5.3 KiB
Python
170 lines
5.3 KiB
Python
"""
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Cretonne shared settings.
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This module defines settings relevant for all code generators.
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"""
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from __future__ import absolute_import
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from cdsl.settings import SettingGroup, BoolSetting, EnumSetting, NumSetting
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group = SettingGroup('shared')
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opt_level = EnumSetting(
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"""
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Optimization level:
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- default: Very profitable optimizations enabled, none slow.
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- best: Enable all optimizations
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- fastest: Optimize for compile time by disabling most optimizations.
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""",
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'default', 'best', 'fastest')
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enable_verifier = BoolSetting(
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"""
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Run the Cretonne IR verifier at strategic times during compilation.
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This makes compilation slower but catches many bugs. The verifier is
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disabled by default, except when reading Cretonne IR from a text file.
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""",
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default=True)
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call_conv = EnumSetting(
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"""
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Default calling convention:
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- fast: not-ABI-stable convention for best performance
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- cold: not-ABI-stable convention for infrequently executed code
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- system_v: System V-style convention used on many platforms
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- windows_fastcall: Windows "fastcall" convention, also used for
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x64 and ARM
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- baldrdash: SpiderMonkey WebAssembly convention
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- probestack: specialized convention for the probestack function
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The default calling convention may be overridden by individual
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functions.
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""",
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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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'baldrdash',
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'probestack'
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)
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# Note that Cretonne doesn't currently need an is_pie flag, because PIE is just
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# 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 valueiables.
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is_pic = BoolSetting("Enable Position-Independent Code generation")
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colocated_libcalls = BoolSetting(
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"""
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Use colocated libcalls.
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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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return_at_end = BoolSetting(
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"""
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Generate functions with at most a single return instruction at the
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end of the function.
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This guarantees that functions do not have any internal return
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instructions. Either they never return, or they have a single return
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instruction at the end.
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""")
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avoid_div_traps = BoolSetting(
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"""
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Generate explicit checks around native division instructions to avoid
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their trapping.
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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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enable_float = BoolSetting(
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"""
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Enable the use of floating-point instructions
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Disabling use of floating-point instructions is not yet implemented.
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""",
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default=True)
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enable_nan_canonicalization = BoolSetting(
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"""
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Enable NaN canonicalization
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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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default=False)
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enable_simd = BoolSetting(
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"""Enable the use of SIMD instructions.""",
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default=True)
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enable_atomics = BoolSetting(
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"""Enable the use of atomic instructions""",
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default=True)
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#
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# Settings specific to the `baldrdash` calling convention.
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#
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baldrdash_prologue_words = NumSetting(
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"""
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Number of pointer-sized words pushed by the baldrdash prologue.
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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 Cretonne-generated code is entered. This includes the
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pushed return address on x86.
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""")
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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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#
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allones_funcaddrs = BoolSetting(
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"""
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Emit not-yet-relocated function addresses as all-ones bit patterns.
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""")
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#
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# Stack probing options.
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#
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probestack_enabled = BoolSetting(
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"""
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Enable the use of stack probes, for calling conventions which support
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this functionality.
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""",
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default=True)
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probestack_func_adjusts_sp = BoolSetting(
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"""
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Set this to true of the stack probe function modifies the stack pointer
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itself.
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""")
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probestack_size_log2 = NumSetting(
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"""
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The log2 of the size of the stack guard region.
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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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default=12)
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group.close(globals())
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