1 //===-- WebAssemblyArgumentMove.cpp - Argument instruction moving ---------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
10 /// This file moves ARGUMENT instructions after ScheduleDAG scheduling.
12 /// Arguments are really live-in registers, however, since we use virtual
13 /// registers and LLVM doesn't support live-in virtual registers, we're
14 /// currently making do with ARGUMENT instructions which are placed at the top
15 /// of the entry block. The trick is to get them to *stay* at the top of the
18 /// The ARGUMENTS physical register keeps these instructions pinned in place
19 /// during liveness-aware CodeGen passes, however one thing which does not
20 /// respect this is the ScheduleDAG scheduler. This pass is therefore run
21 /// immediately after that.
23 /// This is all hopefully a temporary solution until we find a better solution
24 /// for describing the live-in nature of arguments.
26 //===----------------------------------------------------------------------===//
28 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
29 #include "Utils/WebAssemblyUtilities.h"
30 #include "WebAssembly.h"
31 #include "WebAssemblyMachineFunctionInfo.h"
32 #include "WebAssemblySubtarget.h"
33 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
34 #include "llvm/CodeGen/MachineRegisterInfo.h"
35 #include "llvm/CodeGen/Passes.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/raw_ostream.h"
40 #define DEBUG_TYPE "wasm-argument-move"
43 class WebAssemblyArgumentMove final
: public MachineFunctionPass
{
45 static char ID
; // Pass identification, replacement for typeid
46 WebAssemblyArgumentMove() : MachineFunctionPass(ID
) {}
48 StringRef
getPassName() const override
{ return "WebAssembly Argument Move"; }
50 void getAnalysisUsage(AnalysisUsage
&AU
) const override
{
52 AU
.addPreserved
<MachineBlockFrequencyInfo
>();
53 AU
.addPreservedID(MachineDominatorsID
);
54 MachineFunctionPass::getAnalysisUsage(AU
);
57 bool runOnMachineFunction(MachineFunction
&MF
) override
;
59 } // end anonymous namespace
61 char WebAssemblyArgumentMove::ID
= 0;
62 INITIALIZE_PASS(WebAssemblyArgumentMove
, DEBUG_TYPE
,
63 "Move ARGUMENT instructions for WebAssembly", false, false)
65 FunctionPass
*llvm::createWebAssemblyArgumentMove() {
66 return new WebAssemblyArgumentMove();
69 bool WebAssemblyArgumentMove::runOnMachineFunction(MachineFunction
&MF
) {
71 dbgs() << "********** Argument Move **********\n"
72 << "********** Function: " << MF
.getName() << '\n';
76 MachineBasicBlock
&EntryMBB
= MF
.front();
77 MachineBasicBlock::iterator InsertPt
= EntryMBB
.end();
79 // Look for the first NonArg instruction.
80 for (MachineInstr
&MI
: EntryMBB
) {
81 if (!WebAssembly::isArgument(MI
.getOpcode())) {
87 // Now move any argument instructions later in the block
88 // to before our first NonArg instruction.
89 for (MachineInstr
&MI
: llvm::make_range(InsertPt
, EntryMBB
.end())) {
90 if (WebAssembly::isArgument(MI
.getOpcode())) {
91 EntryMBB
.insert(InsertPt
, MI
.removeFromParent());