AsmJit
Low-Latency Machine Code Generation
Core [¶]
Globals, code storage, and emitter interface.
Overview
AsmJit library uses CodeHolder to hold code during code generation and emitters inheriting from BaseEmitter to emit code. CodeHolder uses containers to manage its data:
- Section - stores information about a code or data section.
- CodeBuffer - stores actual code or data, part of Section.
- LabelEntry - stores information about a Label - its name, offset, section where it belongs to, and other bits.
- Fixup - stores information about positions in code that needs to be fixed up later, for example when referencing a Label, which was not bound to a position in code yet.
- RelocEntry - stores information about a relocation.
- AddressTableEntry - stores information about an absolute address, which was used in a jump or call. Code referencing an absolute address may need relocation or a record in address table.
To generate code you would need to instantiate at least the following classes:
- CodeHolder - to hold code during code generation.
- BaseEmitter - to emit code into CodeHolder.
- Target (optional) - most likely JitRuntime to keep the generated code in executable memory. Target can be customized by inheriting from it.
There are also other core classes that are important:
- Environment - describes where the code will run. Environment brings the concept of target triples or tuples into AsmJit, which means that users can specify target architecture, platform, and ABI.
- TypeId - encapsulates lightweight type functionality that can be used to describe primitive and vector types. Types are used by higher level utilities, for example by Function and Compiler.
- CpuInfo - encapsulates CPU information - stores both CPU information and CPU features described by CpuFeatures.
AsmJit also provides global constants:
- Globals - namespace that provides global constants.
- ByteOrder - byte-order constants and functionality.
- Note
- CodeHolder examples use x86::Assembler as abstract interfaces cannot be used to generate code.
CodeHolder & Emitters [¶]
The example below shows how the mentioned classes interact to generate X86 code:
#include <asmjit/x86.h>
#include <stdio.h>
using namespace asmjit;
// Signature of the generated function.
using Func = int (*)(void);
int main() {
JitRuntime rt; // Runtime specialized for JIT code execution.
CodeHolder code; // Holds code and relocation information.
rt.cpuFeatures());
x86::Assembler a(&code); // Create and attach x86::Assembler to code.
a.mov(x86::eax, 1); // Move one to eax register.
a.ret(); // Return from function.
// ===== x86::Assembler is no longer needed from here and can be destroyed =====
Func fn; // Holds address to the generated function.
if (err) return 1; // Handle a possible error returned by AsmJit.
// ===== CodeHolder is no longer needed from here and can be destroyed =====
int result = fn(); // Execute the generated code.
printf("%d\n", result); // Print the resulting "1".
// All classes use RAII, all resources will be released before `main()` returns,
// the generated function can be, however, released explicitly if you intend to
// reuse or keep the runtime alive, which you should in a production-ready code.
rt.release(fn);
return 0;
}
The example above used x86::Assembler as an emitter. AsmJit provides the following emitters that offer various levels of abstraction:
- Assembler - Low-level emitter that emits directly to CodeBuffer.
- Builder - Low-level emitter that emits to a BaseNode list.
- Compiler - High-level emitter that provides register allocation.
Targets and JitRuntime [¶]
AsmJit's Target is an interface that provides basic target abstraction. At the moment AsmJit provides only one implementation called JitRuntime, which as the name suggests provides JIT code target and execution runtime. JitRuntime provides all the necessary stuff to implement a simple JIT compiler with basic memory management. It only provides JitRuntime::add() and JitRuntime::release() functions that are used to either add code to the runtime or release it. JitRuntime doesn't do any decisions on when the code should be released, the decision is up to the developer.
See more at Virtual Memory group.
More About Environment
In the previous example the Environment is retrieved from JitRuntime. It's logical as JitRuntime always returns an Environment that is compatible with the host. For example if your application runs on X86_64 CPU the Environment returned will use Arch::kX64 architecture in contrast to Arch::kX86, which will be used in 32-bit mode on an X86 target.
AsmJit allows to setup the Environment manually and to select a different architecture and ABI when necessary. So let's do something else this time, let's always generate a 32-bit code and print its binary representation. To do that, we can create our own Environment and initialize it to Arch::kX86.
#include <asmjit/x86.h>
#include <stdio.h>
using namespace asmjit;
int main(int argc, char* argv[]) {
using namespace asmjit::x86;
// Create a custom environment initialized to 32-bit X86 architecture.
Environment env;
env.setArch(Arch::kX86);
CodeHolder code; // Create a CodeHolder.
code.init(env); // Initialize CodeHolder with custom environment.
// Generate a 32-bit function that sums 4 floats and looks like:
// void func(float* dst, const float* a, const float* b)
x86::Assembler a(&code); // Create and attach x86::Assembler to `code`.
a.mov(eax, dword_ptr(esp, 4)); // Load the destination pointer.
a.mov(ecx, dword_ptr(esp, 8)); // Load the first source pointer.
a.mov(edx, dword_ptr(esp, 12)); // Load the second source pointer.
a.movups(xmm0, ptr(ecx)); // Load 4 floats from [ecx] to XMM0.
a.movups(xmm1, ptr(edx)); // Load 4 floats from [edx] to XMM1.
a.addps(xmm0, xmm1); // Add 4 floats in XMM1 to XMM0.
a.movups(ptr(eax), xmm0); // Store the result to [eax].
a.ret(); // Return from function.
// We have no Runtime this time, it's on us what we do with the code.
// CodeHolder stores code in Section, which provides some basic properties
// and CodeBuffer structure. We are interested in section's CodeBuffer.
//
// NOTE: The first section is always '.text', it can be retrieved by
// code.sectionById(0) or simply by code.textSection().
// Print the machine-code generated or do something else with it...
// 8B4424048B4C24048B5424040F28010F58010F2900C3
for (size_t i = 0; i < buffer.length; i++)
printf("%02X", buffer.data[i]);
return 0;
}
Explicit Code Relocation [¶]
In addition to Environment, CodeHolder can be configured to specify a base-address (or a virtual base address in a linker terminology), which could be static (useful when you know the location where the target's machine code will be) or dynamic. AsmJit assumes dynamic base-address by default and relocates the code held by CodeHolder to a user provided address on-demand. To be able to relocate to a user provided address it needs to store some information about relocations, which is represented by RelocEntry. Relocation entries are only required if you call external functions from the generated code that cannot be encoded by using a 32-bit displacement (64-bit displacements are not provided by aby supported architecture).
There is also a concept called Fixup - it's a lightweight data structure that doesn't have any identifier and is stored in LabelEntry and CodeHolder as a single-linked list. Fixup represents either a reference to an unbound label and cross-sections references (only relevant to code that uses multiple sections). Since crossing sections is something that cannot be resolved immediately these fixups persist until offsets of these sections are assigned and until CodeHolder::resolveCrossSectionFixups() is called. It's an error if you end up with code that still has fixups after flattening. You can verify it by calling CodeHolder::hasUnresolvedFixups(), which inspects the value returned by CodeHolder::unresolvedFixupCount().
AsmJit can flatten code that uses multiple sections by assigning each section an incrementing offset that respects its alignment. Use CodeHolder::flatten() to do that. After the sections are flattened their offsets and virtual sizes are adjusted to respect each section's buffer size and alignment. The CodeHolder::resolveCrossSectionFixups() function must be called before relocating the code held by CodeHolder. You can also flatten your code manually by iterating over all sections and calculating their offsets (relative to base) by your own algorithm. In that case CodeHolder::flatten() should not be called, however, CodeHolder::resolveCrossSectionFixups() should be.
The example below shows how to use a built-in virtual memory allocator JitAllocator instead of using JitRuntime (just in case you want to use your own memory management) and how to relocate the generated code into your own memory block - you can use your own virtual memory allocator if you prefer that, but that's OS specific and not covered by the documentation.
The following code is similar to the previous one, but implements a function working in both 32-bit and 64-bit environments:
#include <asmjit/x86.h>
#include <stdio.h>
using namespace asmjit;
using SumIntsFunc = void (*)(int* dst, const int* a, const int* b);
int main() {
// Create a custom environment that matches the current host environment.
Environment env = Environment::host();
CodeHolder code; // Create a CodeHolder.
code.init(env, cpuFeatures); // Initialize CodeHolder with environment.
x86::Assembler a(&code); // Create and attach x86::Assembler to `code`.
// Signature: 'void func(int* dst, const int* a, const int* b)'.
x86::Gp dst;
x86::Gp src_a;
x86::Gp src_b;
// Handle the difference between 32-bit and 64-bit calling conventions
// (arguments passed through stack vs. arguments passed by registers).
if (env.is32Bit()) {
dst = x86::eax;
src_a = x86::ecx;
src_b = x86::edx;
a.mov(dst , x86::dword_ptr(x86::esp, 4));
a.mov(src_a, x86::dword_ptr(x86::esp, 8));
a.mov(src_b, x86::dword_ptr(x86::esp, 12));
}
else {
if (env.isPlatformWindows()) {
dst = x86::rcx; // First argument (destination pointer).
src_a = x86::rdx; // Second argument (source 'a' pointer).
src_b = x86::r8; // Third argument (source 'b' pointer).
}
else {
dst = x86::rdi; // First argument (destination pointer).
src_a = x86::rsi; // Second argument (source 'a' pointer).
src_b = x86::rdx; // Third argument (source 'b' pointer).
}
}
a.movdqu(x86::xmm0, x86::ptr(src_a)); // Load 4 ints from [src_a] to XMM0.
a.movdqu(x86::xmm1, x86::ptr(src_b)); // Load 4 ints from [src_b] to XMM1.
a.paddd(x86::xmm0, x86::xmm1); // Add 4 ints in XMM1 to XMM0.
a.movdqu(x86::ptr(dst), x86::xmm0); // Store the result to [dst].
a.ret(); // Return from function.
// Even when we didn't use multiple sections AsmJit could insert one section
// called '.addrtab' (address table section), which would be filled by data
// required by relocations (absolute jumps and calls). You can omit this code
// if you are 100% sure your code doesn't contain multiple sections and
// such relocations. You can use `CodeHolder::hasAddressTable()` to verify
// whether the address table section does exist.
code.flatten();
code.resolveCrossSectionFixups();
// After the code was generated it can be relocated manually to any memory
// location, however, we need to know it's size before we perform memory
// allocation. `CodeHolder::codeSize()` returns the worst estimated code
// size in case that relocations are not possible without trampolines (in
// that case some extra code at the end of the current code buffer is
// generated during relocation).
size_t estimatedSize = code.codeSize();
// Instead of rolling up our own memory allocator we can use the one AsmJit
// provides. It's decoupled so you don't need to use `JitRuntime` for that.
JitAllocator allocator;
// Allocate an executable virtual memory and handle a possible failure.
JitAllocator::Span span;
return 0;
}
// Now relocate the code to the address provided by the memory allocator.
// Please note that this DOESN'T COPY anything to it. This function will
// store the address in CodeHolder and use relocation entries to patch
// the existing code in all sections to respect the base address provided.
code.relocateToBase((uint64_t)span.rx());
// This is purely optional. There are cases in which the relocation can omit
// unneeded data, which would shrink the size of address table. If that
// happened the codeSize returned after relocateToBase() would be smaller
// than the originally `estimatedSize`.
size_t codeSize = code.codeSize();
// This will copy code from all sections to `p`. Iterating over all sections
// and calling `memcpy()` would work as well, however, this function supports
// additional options that can be used to also zero pad sections' virtual
// size, etc.
//
// With some additional features, copyFlattenData() does roughly the following:
//
// allocator.write([&](JitAllocator::Span& span) {
// for (Section* section : code.sections()) {
// uint8_t* p = (uint8_t*)span.rw() + section->offset();
// memcpy(p, section->data(), section->bufferSize());
// }
// }
allocator.write([&](JitAllocator::Span& span) {
});
// Execute the generated function.
int inA[4] = { 4, 3, 2, 1 };
int inB[4] = { 1, 5, 2, 8 };
int out[4];
// This code uses AsmJit's ptr_as_func<> to cast between void* and SumIntsFunc.
SumIntsFunc fn = ptr_as_func<SumIntsFunc>(span.rx());
fn(out, inA, inB);
// Prints {5 8 4 9}
printf("{%d %d %d %d}\n", out[0], out[1], out[2], out[3]);
// Release `fn` is it's no longer needed. It will be destroyed with 'vm'
// instance anyway, but it's a good practice to release it explicitly
// when you know that the function will not be needed anymore.
allocator.release(fn);
return 0;
}
If you know the base-address in advance (before the code generation) it can be passed as a second argument to CodeHolder::init(). In that case the Assembler will know the absolute position of each instruction and would be able to use it during instruction encoding to prevent relocations where possible. The following example shows how to configure the base address:
#include <asmjit/x86.h>
#include <stdio.h>
using namespace asmjit;
void initializeCodeHolder(CodeHolder& code) {
Environment env = Environment::host();
uint64_t baseAddress = uint64_t(0x1234);
// initialize CodeHolder with environment and custom base address.
code.init(env, cpuFeatures, baseAddress);
}
Label Offsets and Links [¶]
When a label that is not yet bound is used by the Assembler, it creates a Fixup, which is then referenced by LabelEntry. Fixups are also created if a label is referenced in a different section than in which it was bound. Let's examine some functions that can be used to check whether there are any unresolved fixups.
#include <asmjit/core.h>
#include <stdio.h>
using namespace asmjit;
// Tests whether the `label` is bound.
bool isBound = code.isLabelBound(label);
// Returns true if the code contains either referenced, but unbound
// labels, or cross-section fixups that are not resolved yet.
printf("Number of unresolved fixups: %zu\n", nUnresolved);
}
There is no function that would return the number of unbound labels as this is completely unimportant from CodeHolder's perspective. If a label is not used then it doesn't matter whether it's bound or not, only actually used labels matter. After a Label is bound it's possible to query its offset relative to the start of the section where it was bound:
#include <asmjit/core.h>
#include <stdio.h>
using namespace asmjit;
// Label offset is known after it's bound. The offset provided is relative
// to the start of the section, see below for alternative. If the given
// label is not bound the offset returned will be zero. It's recommended
// to always check whether the label is bound before using its offset.
uint64_t sectionOffset = code.labelOffset(label);
printf("Label offset relative to section: %llu\n", (unsigned long long)sectionOffset);
// If you use multiple sections and want the offset relative to the base.
// NOTE: This function expects that the section has already an offset and
// the label-link was resolved (if this is not true you will still get an
// offset relative to the start of the section).
uint64_t baseOffset = code.labelOffsetFromBase(label);
printf("Label offset relative to base: %llu\n", (unsigned long long)baseOffset);
}
Code & Data Sections [¶]
AsmJit allows to create multiple sections within the same CodeHolder. A test-case asmjit_test_x86_sections.cpp can be used as a reference point although the following example should also provide a useful insight:
#include <asmjit/x86.h>
#include <stdio.h>
using namespace asmjit;
void sectionsExample(CodeHolder& code) {
// Text section is always provided as the first section.
// To create another section use CodeHolder::newSection().
Section* data;
Error err = code.newSection(&data,
".data", // Section name
SIZE_MAX, // Name length if the name is not null terminated (or SIZE_MAX).
SectionFlags::kNone, // Section flags, see SectionFlags.
8, // Section alignment, must be power of 2.
0); // Section order value (optional, default 0).
// When you switch sections in Assembler, Builder, or Compiler the cursor
// will always move to the end of that section. When you create an Assembler
// the cursor would be placed at the end of the first (.text) section, which
// is initially empty.
x86::Assembler a(&code);
Label L_Data = a.newLabel();
a.mov(x86::eax, x86::ebx); // Emits in .text section.
a.section(data); // Switches to the end of .data section.
a.bind(L_Data); // Binds label in this .data section
a.db(0x01); // Emits byte in .data section.
a.section(text); // Switches to the end of .text section.
a.add(x86::ebx, x86::eax); // Emits in .text section.
// References a label in .text section, which was bound in .data section. This would create a
// fixup even when the L_Data is already bound, because the reference crosses sections. See below...
a.lea(x86::rsi, x86::ptr(L_Data));
}
The last line in the example above shows that a Fixup would be created even for bound labels that cross sections. In this case a referenced label was bound in another section, which means that the reference couldn't be resolved at that moment. If your code uses sections, but you wish AsmJit to flatten these sections (you don't plan to flatten them manually) then there is a ready API for that.
#include <asmjit/x86.h>
#include <stdio.h>
using namespace asmjit;
// ... (continuing the previous example) ...
void sectionsExampleContinued(CodeHolder& code) {
// Suppose we have some code that contains multiple sections and
// we would like to flatten it by using AsmJit's built-in API:
if (err) {
// There are many reasons it can fail, so always handle a possible error.
printf("Failed to flatten the code: %s\n", DebugUtils::errorAsString(err));
exit(1);
}
// After flattening all sections would contain assigned offsets
// relative to base. Offsets are 64-bit unsigned integers so we
// cast them to `size_t` for simplicity. On 32-bit targets it's
// guaranteed that the offset cannot be greater than `2^32 - 1`.
// The flattening doesn't resolve unresolved fixups, this
// has to be done manually as flattening can be done separately.
err = code.resolveCrossSectionFixups();
if (err) {
// This is the kind of error that should always be handled...
printf("Failed to resolve fixups: %s\n", DebugUtils::errorAsString(err));
exit(1);
}
if (code.hasUnresolvedFixups()) {
// This would mean either unbound label or some other issue.
printf("The code has %zu unbound labels\n", code.unresolvedFixupCount());
exit(1);
}
}
Classes
struct ArchTraits
struct CodeBuffer
struct Expression
union Expression::Value
class Section
class AddressTableEntry
struct RelocEntry
class LabelEntry
struct LabelEntry::ExtraData
class CodeHolder
class CpuFeatures
struct CpuFeatures::Data
struct CpuFeatures::X86
struct CpuFeatures::ARM
class CpuInfo
class BaseEmitter
struct BaseEmitter::State
struct BaseEmitter::Funcs
class Environment
struct OffsetFormat
struct Fixup
class Target
struct TypeUtils::TypeData
struct TypeUtils::TypeIdOfT<T>
Macros
#define ASMJIT_LIBRARY_MAKE_VERSION(major, minor, patch)((major<<16) |(minor<<8) |(patch))
#define ASMJIT_LIBRARY_VERSION ASMJIT_LIBRARY_MAKE_VERSION(1, 17, 0)
#define ASMJIT_ABI_NAMESPACE v1_17
#define ASMJIT_API
#define ASMJIT_VIRTAPI
#define ASMJIT_INLINE inline
#define ASMJIT_INLINE_NODEBUG inline
#define ASMJIT_NOINLINE
#define ASMJIT_CDECL
#define ASMJIT_STDCALL
#define ASMJIT_FASTCALL
#define ASMJIT_REGPARM(N)
#define ASMJIT_VECTORCALL
Enumerations
enum class Arch : uint8_t
enum class SubArch : uint8_t
enum class ArchTypeNameId : uint8_t
enum class InstHints : uint8_t
enum class CodeBufferFlags : uint32_t
enum class ExpressionOpType : uint8_t
enum class ExpressionValueType : uint8_t
enum class RelocType : uint32_t
enum class LabelType : uint8_t
enum class LabelFlags : uint8_t
enum class SectionFlags : uint32_t
enum class CopySectionFlags : uint32_t
enum class AlignMode : uint8_t
enum class EmitterType : uint8_t
enum class EmitterFlags : uint8_t
enum class EncodingOptions : uint32_t
enum class DiagnosticOptions : uint32_t
enum class Vendor : uint8_t
enum class Platform : uint8_t
enum class PlatformABI : uint8_t
enum class FloatABI : uint8_t
enum class ObjectFormat : uint8_t
enum class OffsetType : uint8_t
enum class ByteOrder
enum class ResetPolicy : uint32_t
enum class TypeId : uint8_t
#define ASMJIT_LIBRARY_MAKE_VERSION(major, minor, patch)((major<<16) |(minor<<8) |(patch))[¶]
Makes a 32-bit integer that represents AsmJit version in (major << 16) | (minor << 8) | patch form.
#define ASMJIT_LIBRARY_VERSION ASMJIT_LIBRARY_MAKE_VERSION(1, 17, 0)[¶]
AsmJit library version, see ASMJIT_LIBRARY_MAKE_VERSION for a version format reference.
#define ASMJIT_ABI_NAMESPACE v1_17[¶]
AsmJit ABI namespace is an inline namespace within asmjit namespace.
It's used to make sure that when user links to an incompatible version of AsmJit, it won't link. It has also some additional properties as well. When ASMJIT_ABI_NAMESPACE is defined by the user it would override the AsmJit default, which makes it possible to use multiple AsmJit libraries within a single project, totally controlled by users. This is useful especially in cases in which some of such library comes from third party.
#define ASMJIT_API[¶]
A decorator that is used to decorate API that AsmJit exports when built as a shared library.
#define ASMJIT_VIRTAPI[¶]
This is basically a workaround.
When using MSVC and marking class as DLL export everything gets exported, which is unwanted in most projects. MSVC automatically exports typeinfo and vtable if at least one symbol of the class is exported. However, GCC has some strange behavior that even if one or more symbol is exported it doesn't export typeinfo unless the class itself is decorated with "visibility(default)" (i.e. ASMJIT_API).
#define ASMJIT_INLINE inline[¶]
Decorator to force inlining of functions, uses either __attribute__((__always_inline__)) or __forceinline, depending on C++ compiler.
#define ASMJIT_INLINE_NODEBUG inline[¶]
Like ASMJIT_INLINE, but uses additionally __nodebug__ or __artificial__ attribute to make the debugging of some AsmJit functions easier, especially getters and one-line abstractions where usually you don't want to step in.
#define ASMJIT_INLINE_CONSTEXPR constexpr ASMJIT_INLINE_NODEBUG[¶]
Like ASMJIT_INLINE_NODEBUG, but having an additional constexpr attribute.
#define ASMJIT_NOINLINE[¶]
Decorator to avoid inlining of functions, uses either __attribute__((__noinline__)) or __declspec(noinline) depending on C++ compiler.
#define ASMJIT_CDECL[¶]
CDECL function attribute - either __attribute__((__cdecl__)) or __cdecl.
#define ASMJIT_STDCALL[¶]
STDCALL function attribute - either __attribute__((__stdcall__)) or __stdcall.
- Note
- This expands to nothing on non-x86 targets as STDCALL is X86 specific.
#define ASMJIT_FASTCALL[¶]
FASTCALL function attribute - either __attribute__((__fastcall__)) or __fastcall.
- Note
- Expands to nothing on non-x86 targets as FASTCALL is X86 specific.
#define ASMJIT_REGPARM(N)[¶]
Expands to __attribute__((__regparm__(N))) when compiled by GCC or clang, nothing otherwise.
#define ASMJIT_VECTORCALL[¶]
VECTORCALL function attribute - either __attribute__((__vectorcall__)) or __vectorcall.
- Note
- Expands to nothing on non-x86 targets as VECTORCALL is X86 specific.
class Arch : uint8_tenumstrong[¶]
Instruction set architecture (ISA).
class ArchTypeNameId : uint8_tenumstrong[¶]
Identifier used to represent names of different data types across architectures.
class InstHints : uint8_tenumstrong[¶]
Instruction feature hints for each register group provided by ArchTraits.
Instruction feature hints describe miscellaneous instructions provided by the architecture that can be used by register allocator to make certain things simpler - like register swaps or emitting register push/pop sequences.
- Remarks
- Instruction feature hints are only defined for register groups that can be used with Compiler infrastructure. Register groups that are not managed by Compiler are not provided by ArchTraits and cannot be queried.
| Constant | Description |
|---|---|
| kNoHints | No feature hints. |
| kRegSwap | Architecture supports a register swap by using a single instruction. |
| kPushPop | Architecture provides push/pop instructions. |
class CodeBufferFlags : uint32_tenumstrong[¶]
Flags used by CodeBuffer.
| Constant | Description |
|---|---|
| kNone | No flags. |
| kIsExternal | Buffer is external (not allocated by asmjit). |
| kIsFixed | Buffer is fixed (cannot be reallocated). |
class ExpressionOpType : uint8_tenumstrong[¶]
Operator type that can be used within an Expression.
| Constant | Description |
|---|---|
| kAdd | Addition. |
| kSub | Subtraction. |
| kMul | Multiplication. |
| kSll | Logical left shift. |
| kSrl | Logical right shift. |
| kSra | Arithmetic right shift. |
class ExpressionValueType : uint8_tenumstrong[¶]
Value type that can be used within an Expression.
| Constant | Description |
|---|---|
| kNone | No value or invalid. |
| kConstant | Value is 64-bit unsigned integer (constant). |
| kLabel | Value is LabelEntry, which references a Label. |
| kExpression | Value is Expression. |
class RelocType : uint32_tenumstrong[¶]
Relocation type.
class LabelType : uint8_tenumstrong[¶]
Type of the Label.
class LabelFlags : uint8_tenumstrong[¶]
Label flags describe some details about labels used by LabelEntry, mostly for AsmJit's own use.
class SectionFlags : uint32_tenumstrong[¶]
Section flags, used by Section.
| Constant | Description |
|---|---|
| kNone | No flags. |
| kExecutable | Executable (.text sections). |
| kReadOnly | Read-only (.text and .data sections). |
| kZeroInitialized | Zero initialized by the loader (BSS). |
| kComment | Info / comment flag. |
| kBuiltIn | Section is built in and created by default (.text section). |
| kImplicit | Section created implicitly, can be deleted by Target. |
class CopySectionFlags : uint32_tenumstrong[¶]
Flags that can be used with CodeHolder::copySectionData() and CodeHolder::copyFlattenedData().
| Constant | Description |
|---|---|
| kNone | No flags. |
| kPadSectionBuffer | If virtual size of a section is greater than the size of its CodeBuffer then all bytes between the buffer size and virtual size will be zeroed. If this option is not set then those bytes would be left as is, which means that if the user didn't initialize them they would have a previous content, which may be unwanted. |
| kPadTargetBuffer | Clears the target buffer if the flattened data is less than the destination size. This option works only with CodeHolder::copyFlattenedData() as it processes multiple sections. It is ignored by CodeHolder::copySectionData(). |
class AlignMode : uint8_tenumstrong[¶]
Align mode, used by BaseEmitter::align().
| Constant | Description |
|---|---|
| kCode | Align executable code. |
| kData | Align non-executable code. |
| kZero | Align by a sequence of zeros. |
| kMaxValue | Maximum value of |
class EmitterType : uint8_tenumstrong[¶]
Emitter type used by BaseEmitter.
| Constant | Description |
|---|---|
| kNone | Unknown or uninitialized. |
| kAssembler | Emitter inherits from BaseAssembler. |
| kBuilder | Emitter inherits from BaseBuilder. |
| kCompiler | Emitter inherits from BaseCompiler. |
| kMaxValue | Maximum value of |
class EmitterFlags : uint8_tenumstrong[¶]
Emitter flags, used by BaseEmitter.
| Constant | Description |
|---|---|
| kNone | No flags. |
| kAttached | Emitter is attached to CodeHolder. |
| kLogComments | The emitter must emit comments. |
| kOwnLogger | The emitter has its own Logger (not propagated from CodeHolder). |
| kOwnErrorHandler | The emitter has its own ErrorHandler (not propagated from CodeHolder). |
| kFinalized | The emitter was finalized. |
| kDestroyed | The emitter was destroyed. This flag is used for a very short time when an emitter is being destroyed by CodeHolder. |
class EncodingOptions : uint32_tenumstrong[¶]
Encoding options.
class DiagnosticOptions : uint32_tenumstrong[¶]
Diagnostic options are used to tell emitters and their passes to perform diagnostics when emitting or processing user code.
These options control validation and extra diagnostics that can be performed by higher level emitters.
Instruction Validation
BaseAssembler implementation perform by default only basic checks that are necessary to identify all variations of an instruction so the correct encoding can be selected. This is fine for production-ready code as the assembler doesn't have to perform checks that would slow it down. However, sometimes these checks are beneficial especially when the project that uses AsmJit is in a development phase, in which mistakes happen often. To make the experience of using AsmJit seamless it offers validation features that can be controlled by DiagnosticOptions.
Compiler Diagnostics
Diagnostic options work with BaseCompiler passes (precisely with its register allocation pass). These options can be used to enable logging of all operations that the Compiler does.
| Constant | Description |
|---|---|
| kNone | No validation options. |
| kValidateAssembler | Perform strict validation in BaseAssembler::emit() implementations. This flag ensures that each instruction is checked before it's encoded into a binary representation. This flag is only relevant for BaseAssembler implementations, but can be set in any other emitter type, in that case if that emitter needs to create an assembler on its own, for the purpose of BaseEmitter::finalize() it would propagate this flag to such assembler so all instructions passed to it are explicitly validated. Default: false. |
| kValidateIntermediate | Perform strict validation in BaseBuilder::emit() and BaseCompiler::emit() implementations. This flag ensures that each instruction is checked before an InstNode representing the instruction is created by BaseBuilder or BaseCompiler. This option could be more useful than kValidateAssembler in cases in which there is an invalid instruction passed to an assembler, which was invalid much earlier, most likely when such instruction was passed to Builder/Compiler. This is a separate option that was introduced, because it's possible to manipulate the instruction stream emitted by BaseBuilder and BaseCompiler - this means that it's allowed to emit invalid instructions (for example with missing operands) that will be fixed later before finalizing it. Default: false. |
| kRAAnnotate | Annotate all nodes processed by register allocator (Compiler/RA).
|
| kRADebugCFG | Debug CFG generation and other related algorithms / operations (Compiler/RA). |
| kRADebugLiveness | Debug liveness analysis (Compiler/RA). |
| kRADebugAssignment | Debug register allocation assignment (Compiler/RA). |
| kRADebugUnreachable | Debug the removal of code part of unreachable blocks. |
| kRADebugAll | Enable all debug options (Compiler/RA). |
class Platform : uint8_tenumstrong[¶]
Platform - runtime environment or operating system.
class PlatformABI : uint8_tenumstrong[¶]
Platform ABI (application binary interface).
class ObjectFormat : uint8_tenumstrong[¶]
Object format.
- Note
- AsmJit doesn't really use anything except ObjectFormat::kUnknown and ObjectFormat::kJIT at the moment. Object file formats are provided for future extensibility and a possibility to generate object files at some point.
| Constant | Description |
|---|---|
| kUnknown | Unknown or uninitialized object format. |
| kJIT | JIT code generation object, most likely JitRuntime or a custom Target implementation. |
| kELF | Executable and linkable format (ELF). |
| kCOFF | Common object file format. |
| kXCOFF | Extended COFF object format. |
| kMachO | Mach object file format. |
| kMaxValue | Maximum value of |
class OffsetType : uint8_tenumstrong[¶]
Offset format type, used by OffsetFormat.
class ResetPolicy : uint32_tenumstrong[¶]
class TypeId : uint8_tenumstrong[¶]
Type identifier provides a minimalist type system used across AsmJit library.
This is an additional information that can be used to describe a value-type of physical or virtual register. It's used mostly by BaseCompiler to describe register representation (the group of data stored in the register and the width used) and it's also used by APIs that allow to describe and work with function signatures.
template<typename Func>Func ptr_as_func(void* func)staticnoexcept[¶]
Casts a void* pointer func to a function pointer Func.
template<typename Func>void* func_as_ptr(Func func)staticnoexcept[¶]
Casts a function pointer func to a void pointer void*.