LLVM 20.0.0git
WebAssemblyArgumentMove.cpp
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1//===-- WebAssemblyArgumentMove.cpp - Argument instruction moving ---------===//
2//
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
6//
7//===----------------------------------------------------------------------===//
8///
9/// \file
10/// This file moves ARGUMENT instructions after ScheduleDAG scheduling.
11///
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
16/// entry block.
17///
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.
22///
23/// This is all hopefully a temporary solution until we find a better solution
24/// for describing the live-in nature of arguments.
25///
26//===----------------------------------------------------------------------===//
27
29#include "WebAssembly.h"
35#include "llvm/CodeGen/Passes.h"
36#include "llvm/Support/Debug.h"
38using namespace llvm;
39
40#define DEBUG_TYPE "wasm-argument-move"
41
42namespace {
43class WebAssemblyArgumentMove final : public MachineFunctionPass {
44public:
45 static char ID; // Pass identification, replacement for typeid
46 WebAssemblyArgumentMove() : MachineFunctionPass(ID) {}
47
48 StringRef getPassName() const override { return "WebAssembly Argument Move"; }
49
50 void getAnalysisUsage(AnalysisUsage &AU) const override {
51 AU.setPreservesCFG();
55 }
56
57 bool runOnMachineFunction(MachineFunction &MF) override;
58};
59} // end anonymous namespace
60
61char WebAssemblyArgumentMove::ID = 0;
62INITIALIZE_PASS(WebAssemblyArgumentMove, DEBUG_TYPE,
63 "Move ARGUMENT instructions for WebAssembly", false, false)
64
66 return new WebAssemblyArgumentMove();
67}
68
69bool WebAssemblyArgumentMove::runOnMachineFunction(MachineFunction &MF) {
71 dbgs() << "********** Argument Move **********\n"
72 << "********** Function: " << MF.getName() << '\n';
73 });
74
75 bool Changed = false;
76 MachineBasicBlock &EntryMBB = MF.front();
77 MachineBasicBlock::iterator InsertPt = EntryMBB.end();
78
79 // Look for the first NonArg instruction.
80 for (MachineInstr &MI : EntryMBB) {
81 if (!WebAssembly::isArgument(MI.getOpcode())) {
82 InsertPt = MI;
83 break;
84 }
85 }
86
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());
92 Changed = true;
93 }
94 }
95
96 return Changed;
97}
#define LLVM_DEBUG(X)
Definition: Debug.h:101
IRTranslator LLVM IR MI
#define INITIALIZE_PASS(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:38
#define DEBUG_TYPE
This file provides WebAssembly-specific target descriptions.
This file declares WebAssembly-specific per-machine-function information.
This file declares the WebAssembly-specific subclass of TargetSubtarget.
This file contains the declaration of the WebAssembly-specific utility functions.
This file contains the entry points for global functions defined in the LLVM WebAssembly back-end.
Represent the analysis usage information of a pass.
AnalysisUsage & addPreservedID(const void *ID)
AnalysisUsage & addPreserved()
Add the specified Pass class to the set of analyses preserved by this pass.
void setPreservesCFG()
This function should be called by the pass, iff they do not:
Definition: Pass.cpp:269
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:311
MachineFunctionPass - This class adapts the FunctionPass interface to allow convenient creation of pa...
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - Subclasses that override getAnalysisUsage must call this.
virtual bool runOnMachineFunction(MachineFunction &MF)=0
runOnMachineFunction - This method must be overloaded to perform the desired machine code transformat...
StringRef getName() const
getName - Return the name of the corresponding LLVM function.
const MachineBasicBlock & front() const
Representation of each machine instruction.
Definition: MachineInstr.h:69
virtual StringRef getPassName() const
getPassName - Return a nice clean name for a pass.
Definition: Pass.cpp:81
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
unsigned ID
LLVM IR allows to use arbitrary numbers as calling convention identifiers.
Definition: CallingConv.h:24
bool isArgument(unsigned Opc)
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
char & MachineDominatorsID
MachineDominators - This pass is a machine dominators analysis pass.
iterator_range< T > make_range(T x, T y)
Convenience function for iterating over sub-ranges.
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163
FunctionPass * createWebAssemblyArgumentMove()