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2f3b03882d
Summary: It does not currently make sense to use WebAssembly features in some functions but not others, so this CL adds an IR pass that takes the union of all used feature sets and applies it to each function in the module. This allows us to prevent atomics from being lowered away if some function has opted in to using them. When atomics is not enabled anywhere, we detect whether there exists any atomic operations or thread local storage that would be stripped and disallow linking with objects that contain atomics if and only if atomics or tls are stripped. When atomics is enabled, mark it as used but do not require it of other objects in the link. These changes allow libraries that do not use atomics to be built once and linked into both single-threaded and multithreaded binaries. Reviewers: aheejin, sbc100, dschuff Subscribers: jgravelle-google, hiraditya, sunfish, jfb, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D59625 llvm-svn: 357226
60 lines
2.1 KiB
C++
60 lines
2.1 KiB
C++
//===-- WebAssemblySubtarget.cpp - WebAssembly Subtarget Information ------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// This file implements the WebAssembly-specific subclass of
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/// TargetSubtarget.
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///
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//===----------------------------------------------------------------------===//
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#include "WebAssemblySubtarget.h"
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#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
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#include "WebAssemblyInstrInfo.h"
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#include "llvm/Support/TargetRegistry.h"
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using namespace llvm;
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#define DEBUG_TYPE "wasm-subtarget"
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#define GET_SUBTARGETINFO_CTOR
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#define GET_SUBTARGETINFO_TARGET_DESC
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#include "WebAssemblyGenSubtargetInfo.inc"
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WebAssemblySubtarget &
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WebAssemblySubtarget::initializeSubtargetDependencies(StringRef FS) {
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// Determine default and user-specified characteristics
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if (CPUString.empty())
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CPUString = "generic";
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ParseSubtargetFeatures(CPUString, FS);
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return *this;
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}
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WebAssemblySubtarget::WebAssemblySubtarget(const Triple &TT,
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const std::string &CPU,
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const std::string &FS,
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const TargetMachine &TM)
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: WebAssemblyGenSubtargetInfo(TT, CPU, FS), CPUString(CPU),
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TargetTriple(TT), FrameLowering(),
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InstrInfo(initializeSubtargetDependencies(FS)), TSInfo(),
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TLInfo(TM, *this) {}
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bool WebAssemblySubtarget::enableAtomicExpand() const {
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// If atomics are disabled, atomic ops are lowered instead of expanded
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return hasAtomics();
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}
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bool WebAssemblySubtarget::enableMachineScheduler() const {
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// Disable the MachineScheduler for now. Even with ShouldTrackPressure set and
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// enableMachineSchedDefaultSched overridden, it appears to have an overall
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// negative effect for the kinds of register optimizations we're doing.
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return false;
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}
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bool WebAssemblySubtarget::useAA() const { return true; }
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