mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-23 11:13:28 +01:00
0c5cac5f91
Summary:
Thread local variables are placed inside a `.tdata` segment. Their symbols are
offsets from the start of the segment. The address of a thread local variable
is computed as `__tls_base` + the offset from the start of the segment.
`.tdata` segment is a passive segment and `memory.init` is used once per thread
to initialize the thread local storage.
`__tls_base` is a wasm global. Since each thread has its own wasm instance,
it is effectively thread local. Currently, `__tls_base` must be initialized
at thread startup, and so cannot be used with dynamic libraries.
`__tls_base` is to be initialized with a new linker-synthesized function,
`__wasm_init_tls`, which takes as an argument a block of memory to use as the
storage for thread locals. It then initializes the block of memory and sets
`__tls_base`. As `__wasm_init_tls` will handle the memory initialization,
the memory does not have to be zeroed.
To help allocating memory for thread-local storage, a new compiler intrinsic
is introduced: `__builtin_wasm_tls_size()`. This instrinsic function returns
the size of the thread-local storage for the current function.
The expected usage is to run something like the following upon thread startup:
__wasm_init_tls(malloc(__builtin_wasm_tls_size()));
Reviewers: tlively, aheejin, kripken, sbc100
Subscribers: dschuff, jgravelle-google, hiraditya, sunfish, jfb, cfe-commits, llvm-commits
Tags: #clang, #llvm
Differential Revision: https://reviews.llvm.org/D64537
llvm-svn: 366272
96 lines
3.0 KiB
C++
96 lines
3.0 KiB
C++
//===- MCSectionWasm.h - Wasm Machine Code Sections -------------*- C++ -*-===//
|
|
//
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file declares the MCSectionWasm class.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef LLVM_MC_MCSECTIONWASM_H
|
|
#define LLVM_MC_MCSECTIONWASM_H
|
|
|
|
#include "llvm/ADT/Twine.h"
|
|
#include "llvm/MC/MCSection.h"
|
|
#include "llvm/MC/MCSymbolWasm.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
|
|
namespace llvm {
|
|
|
|
class MCSymbol;
|
|
|
|
/// This represents a section on wasm.
|
|
class MCSectionWasm final : public MCSection {
|
|
/// This is the name of the section. The referenced memory is owned by
|
|
/// TargetLoweringObjectFileWasm's WasmUniqueMap.
|
|
StringRef SectionName;
|
|
|
|
unsigned UniqueID;
|
|
|
|
const MCSymbolWasm *Group;
|
|
|
|
// The offset of the MC function/data section in the wasm code/data section.
|
|
// For data relocations the offset is relative to start of the data payload
|
|
// itself and does not include the size of the section header.
|
|
uint64_t SectionOffset = 0;
|
|
|
|
// For data sections, this is the index of of the corresponding wasm data
|
|
// segment
|
|
uint32_t SegmentIndex = 0;
|
|
|
|
// Whether this data segment is passive
|
|
bool IsPassive = false;
|
|
|
|
friend class MCContext;
|
|
MCSectionWasm(StringRef Section, SectionKind K, const MCSymbolWasm *group,
|
|
unsigned UniqueID, MCSymbol *Begin)
|
|
: MCSection(SV_Wasm, K, Begin), SectionName(Section), UniqueID(UniqueID),
|
|
Group(group) {}
|
|
|
|
public:
|
|
/// Decides whether a '.section' directive should be printed before the
|
|
/// section name
|
|
bool shouldOmitSectionDirective(StringRef Name, const MCAsmInfo &MAI) const;
|
|
|
|
StringRef getSectionName() const { return SectionName; }
|
|
const MCSymbolWasm *getGroup() const { return Group; }
|
|
|
|
void PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
|
|
raw_ostream &OS,
|
|
const MCExpr *Subsection) const override;
|
|
bool UseCodeAlign() const override;
|
|
bool isVirtualSection() const override;
|
|
|
|
bool isWasmData() const {
|
|
return Kind.isGlobalWriteableData() || Kind.isReadOnly() ||
|
|
Kind.isThreadLocal();
|
|
}
|
|
|
|
bool isUnique() const { return UniqueID != ~0U; }
|
|
unsigned getUniqueID() const { return UniqueID; }
|
|
|
|
uint64_t getSectionOffset() const { return SectionOffset; }
|
|
void setSectionOffset(uint64_t Offset) { SectionOffset = Offset; }
|
|
|
|
uint32_t getSegmentIndex() const { return SegmentIndex; }
|
|
void setSegmentIndex(uint32_t Index) { SegmentIndex = Index; }
|
|
|
|
bool getPassive() const {
|
|
assert(isWasmData());
|
|
return IsPassive;
|
|
}
|
|
void setPassive(bool V = true) {
|
|
assert(isWasmData());
|
|
IsPassive = V;
|
|
}
|
|
static bool classof(const MCSection *S) { return S->getVariant() == SV_Wasm; }
|
|
};
|
|
|
|
} // end namespace llvm
|
|
|
|
#endif
|