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llvm-mirror/lib/Target/WebAssembly/WebAssemblyArgumentMove.cpp
Heejin Ahn 37702c2638 [WebAssembly] Put utility functions in Utils directory (NFC)
This CL
1. Creates Utils/ directory under lib/Target/WebAssembly
2. Moves existing WebAssemblyUtilities.cpp|h into the Utils/ directory
3. Creates Utils/WebAssemblyTypeUtilities.cpp|h and put type
   declarataions and type conversion functions scattered in various
   places into this single place.

It has been suggested several times that it is not easy to share utility
functions between subdirectories (AsmParser, DIsassembler, MCTargetDesc,
...). Sometimes we ended up [[ https://reviews.llvm.org/D92840#2478863 | duplicating ]] the same function because of
this.

There are already other targets doing this: AArch64, AMDGPU, and ARM
have Utils/ subdirectory under their target directory.

This extracts the utility functions into a single directory Utils/ and
make them sharable among all passes in WebAssembly/ and its
subdirectories. Also I believe gathering all type-related conversion
functionalities into a single place makes it more usable. (Actually I
was working on another CL that uses various type conversion functions
scattered in multiple places, which became the motivation for this CL.)

Reviewed By: dschuff, aardappel

Differential Revision: https://reviews.llvm.org/D100995
2021-04-22 15:29:43 -07:00

98 lines
3.4 KiB
C++

//===-- WebAssemblyArgumentMove.cpp - Argument instruction moving ---------===//
//
// 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 moves ARGUMENT instructions after ScheduleDAG scheduling.
///
/// Arguments are really live-in registers, however, since we use virtual
/// registers and LLVM doesn't support live-in virtual registers, we're
/// currently making do with ARGUMENT instructions which are placed at the top
/// of the entry block. The trick is to get them to *stay* at the top of the
/// entry block.
///
/// The ARGUMENTS physical register keeps these instructions pinned in place
/// during liveness-aware CodeGen passes, however one thing which does not
/// respect this is the ScheduleDAG scheduler. This pass is therefore run
/// immediately after that.
///
/// This is all hopefully a temporary solution until we find a better solution
/// for describing the live-in nature of arguments.
///
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "Utils/WebAssemblyUtilities.h"
#include "WebAssembly.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblySubtarget.h"
#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "wasm-argument-move"
namespace {
class WebAssemblyArgumentMove final : public MachineFunctionPass {
public:
static char ID; // Pass identification, replacement for typeid
WebAssemblyArgumentMove() : MachineFunctionPass(ID) {}
StringRef getPassName() const override { return "WebAssembly Argument Move"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addPreserved<MachineBlockFrequencyInfo>();
AU.addPreservedID(MachineDominatorsID);
MachineFunctionPass::getAnalysisUsage(AU);
}
bool runOnMachineFunction(MachineFunction &MF) override;
};
} // end anonymous namespace
char WebAssemblyArgumentMove::ID = 0;
INITIALIZE_PASS(WebAssemblyArgumentMove, DEBUG_TYPE,
"Move ARGUMENT instructions for WebAssembly", false, false)
FunctionPass *llvm::createWebAssemblyArgumentMove() {
return new WebAssemblyArgumentMove();
}
bool WebAssemblyArgumentMove::runOnMachineFunction(MachineFunction &MF) {
LLVM_DEBUG({
dbgs() << "********** Argument Move **********\n"
<< "********** Function: " << MF.getName() << '\n';
});
bool Changed = false;
MachineBasicBlock &EntryMBB = MF.front();
MachineBasicBlock::iterator InsertPt = EntryMBB.end();
// Look for the first NonArg instruction.
for (MachineInstr &MI : EntryMBB) {
if (!WebAssembly::isArgument(MI.getOpcode())) {
InsertPt = MI;
break;
}
}
// Now move any argument instructions later in the block
// to before our first NonArg instruction.
for (MachineInstr &MI : llvm::make_range(InsertPt, EntryMBB.end())) {
if (WebAssembly::isArgument(MI.getOpcode())) {
EntryMBB.insert(InsertPt, MI.removeFromParent());
Changed = true;
}
}
return Changed;
}