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llvm-mirror/lib/Target/WebAssembly/WebAssemblySubtarget.cpp
Craig Topper 10839866a1 [X86][MC][Target] Initial backend support a tune CPU to support -mtune
This patch implements initial backend support for a -mtune CPU controlled by a "tune-cpu" function attribute. If the attribute is not present X86 will use the resolved CPU from target-cpu attribute or command line.

This patch adds MC layer support a tune CPU. Each CPU now has two sets of features stored in their GenSubtargetInfo.inc tables . These features lists are passed separately to the Processor and ProcessorModel classes in tablegen. The tune list defaults to an empty list to avoid changes to non-X86. This annoyingly increases the size of static tables on all target as we now store 24 more bytes per CPU. I haven't quantified the overall impact, but I can if we're concerned.

One new test is added to X86 to show a few tuning features with mismatched tune-cpu and target-cpu/target-feature attributes to demonstrate independent control. Another new test is added to demonstrate that the scheduler model follows the tune CPU.

I have not added a -mtune to llc/opt or MC layer command line yet. With no attributes we'll just use the -mcpu for both. MC layer tools will always follow the normal CPU for tuning.

Differential Revision: https://reviews.llvm.org/D85165
2020-08-14 15:31:50 -07:00

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//===-- WebAssemblySubtarget.cpp - WebAssembly Subtarget Information ------===//
//
// 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
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file implements the WebAssembly-specific subclass of
/// TargetSubtarget.
///
//===----------------------------------------------------------------------===//
#include "WebAssemblySubtarget.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "WebAssemblyInstrInfo.h"
#include "llvm/Support/TargetRegistry.h"
using namespace llvm;
#define DEBUG_TYPE "wasm-subtarget"
#define GET_SUBTARGETINFO_CTOR
#define GET_SUBTARGETINFO_TARGET_DESC
#include "WebAssemblyGenSubtargetInfo.inc"
WebAssemblySubtarget &
WebAssemblySubtarget::initializeSubtargetDependencies(StringRef CPU,
StringRef FS) {
// Determine default and user-specified characteristics
LLVM_DEBUG(llvm::dbgs() << "initializeSubtargetDependencies\n");
if (CPU.empty())
CPU = "generic";
ParseSubtargetFeatures(CPU, /*TuneCPU*/ CPU, FS);
return *this;
}
WebAssemblySubtarget::WebAssemblySubtarget(const Triple &TT,
const std::string &CPU,
const std::string &FS,
const TargetMachine &TM)
: WebAssemblyGenSubtargetInfo(TT, CPU, /*TuneCPU*/ CPU, FS),
TargetTriple(TT), FrameLowering(),
InstrInfo(initializeSubtargetDependencies(CPU, FS)), TSInfo(),
TLInfo(TM, *this) {}
bool WebAssemblySubtarget::enableAtomicExpand() const {
// If atomics are disabled, atomic ops are lowered instead of expanded
return hasAtomics();
}
bool WebAssemblySubtarget::enableMachineScheduler() const {
// Disable the MachineScheduler for now. Even with ShouldTrackPressure set and
// enableMachineSchedDefaultSched overridden, it appears to have an overall
// negative effect for the kinds of register optimizations we're doing.
return false;
}
bool WebAssemblySubtarget::useAA() const { return true; }