LLVM 20.0.0git
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SIInsertWaitcnts.cpp File Reference

Insert wait instructions for memory reads and writes. More...

#include "AMDGPU.h"
#include "GCNSubtarget.h"
#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
#include "SIMachineFunctionInfo.h"
#include "Utils/AMDGPUBaseInfo.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/Sequence.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachinePostDominators.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/DebugCounter.h"
#include "llvm/TargetParser/TargetParser.h"

Go to the source code of this file.

Classes

struct  llvm::enum_iteration_traits< InstCounterType >
 

Namespaces

namespace  llvm
 This is an optimization pass for GlobalISel generic memory operations.
 

Macros

#define DEBUG_TYPE   "si-insert-waitcnts"
 

Functions

 DEBUG_COUNTER (ForceExpCounter, DEBUG_TYPE"-forceexp", "Force emit s_waitcnt expcnt(0) instrs")
 
 DEBUG_COUNTER (ForceLgkmCounter, DEBUG_TYPE"-forcelgkm", "Force emit s_waitcnt lgkmcnt(0) instrs")
 
 DEBUG_COUNTER (ForceVMCounter, DEBUG_TYPE"-forcevm", "Force emit s_waitcnt vmcnt(0) instrs")
 
 INITIALIZE_PASS_BEGIN (SIInsertWaitcnts, DEBUG_TYPE, "SI Insert Waitcnts", false, false) INITIALIZE_PASS_END(SIInsertWaitcnts
 
static bool updateOperandIfDifferent (MachineInstr &MI, uint16_t OpName, unsigned NewEnc)
 
static std::optional< InstCounterType > counterTypeForInstr (unsigned Opcode)
 Determine if MI is a gfx12+ single-counter S_WAIT_*CNT instruction, and if so, which counter it is waiting on.
 
static bool readsVCCZ (const MachineInstr &MI)
 
static bool callWaitsOnFunctionEntry (const MachineInstr &MI)
 
static bool callWaitsOnFunctionReturn (const MachineInstr &MI)
 
static bool isCacheInvOrWBInst (MachineInstr &Inst)
 
static bool isWaitInstr (MachineInstr &Inst)
 

Variables

static cl::opt< boolForceEmitZeroFlag ("amdgpu-waitcnt-forcezero", cl::desc("Force all waitcnt instrs to be emitted as s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)"), cl::init(false), cl::Hidden)
 
 DEBUG_TYPE
 
SI Insert Waitcnts
 
SI Insert false
 

Detailed Description

Insert wait instructions for memory reads and writes.

Memory reads and writes are issued asynchronously, so we need to insert S_WAITCNT instructions when we want to access any of their results or overwrite any register that's used asynchronously.

TODO: This pass currently keeps one timeline per hardware counter. A more finely-grained approach that keeps one timeline per event type could sometimes get away with generating weaker s_waitcnt instructions. For example, when both SMEM and LDS are in flight and we need to wait for the i-th-last LDS instruction, then an lgkmcnt(i) is actually sufficient, but the pass will currently generate a conservative lgkmcnt(0) because multiple event types are in flight.

Definition in file SIInsertWaitcnts.cpp.

Macro Definition Documentation

◆ DEBUG_TYPE

#define DEBUG_TYPE   "si-insert-waitcnts"

Definition at line 42 of file SIInsertWaitcnts.cpp.

Function Documentation

◆ callWaitsOnFunctionEntry()

static bool callWaitsOnFunctionEntry ( const MachineInstr MI)
static
Returns
true if the callee inserts an s_waitcnt 0 on function entry.

Definition at line 1586 of file SIInsertWaitcnts.cpp.

◆ callWaitsOnFunctionReturn()

static bool callWaitsOnFunctionReturn ( const MachineInstr MI)
static
Returns
true if the callee is expected to wait for any outstanding waits before returning.

Definition at line 1596 of file SIInsertWaitcnts.cpp.

◆ counterTypeForInstr()

static std::optional< InstCounterType > counterTypeForInstr ( unsigned  Opcode)
static

Determine if MI is a gfx12+ single-counter S_WAIT_*CNT instruction, and if so, which counter it is waiting on.

Definition at line 1150 of file SIInsertWaitcnts.cpp.

Referenced by isWaitInstr().

◆ DEBUG_COUNTER() [1/3]

DEBUG_COUNTER ( ForceExpCounter  ,
DEBUG_TYPE"-forceexp"  ,
"Force emit s_waitcnt expcnt(0) instrs"   
)

◆ DEBUG_COUNTER() [2/3]

DEBUG_COUNTER ( ForceLgkmCounter  ,
DEBUG_TYPE"-forcelgkm"  ,
"Force emit s_waitcnt lgkmcnt(0) instrs"   
)

◆ DEBUG_COUNTER() [3/3]

DEBUG_COUNTER ( ForceVMCounter  ,
DEBUG_TYPE"-forcevm"  ,
"Force emit s_waitcnt vmcnt(0) instrs"   
)

◆ INITIALIZE_PASS_BEGIN()

INITIALIZE_PASS_BEGIN ( SIInsertWaitcnts  ,
DEBUG_TYPE  ,
"SI Insert Waitcnts"  ,
false  ,
false   
)

◆ isCacheInvOrWBInst()

static bool isCacheInvOrWBInst ( MachineInstr Inst)
static

Definition at line 1974 of file SIInsertWaitcnts.cpp.

References llvm::MachineInstr::getOpcode().

◆ isWaitInstr()

static bool isWaitInstr ( MachineInstr Inst)
static

◆ readsVCCZ()

static bool readsVCCZ ( const MachineInstr MI)
static

Definition at line 1579 of file SIInsertWaitcnts.cpp.

References MI.

◆ updateOperandIfDifferent()

static bool updateOperandIfDifferent ( MachineInstr MI,
uint16_t  OpName,
unsigned  NewEnc 
)
static

Variable Documentation

◆ DEBUG_TYPE

DEBUG_TYPE

Definition at line 1123 of file SIInsertWaitcnts.cpp.

◆ false

SI Insert false

Definition at line 1123 of file SIInsertWaitcnts.cpp.

◆ ForceEmitZeroFlag

cl::opt< bool > ForceEmitZeroFlag("amdgpu-waitcnt-forcezero", cl::desc("Force all waitcnt instrs to be emitted as s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)"), cl::init(false), cl::Hidden) ( "amdgpu-waitcnt-forcezero"  ,
cl::desc("Force all waitcnt instrs to be emitted as s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)")  ,
cl::init(false)  ,
cl::Hidden   
)
static

◆ Waitcnts

SI Insert Waitcnts

Definition at line 1123 of file SIInsertWaitcnts.cpp.