LLVM 19.0.0git
Macros | Typedefs | Functions | Variables
CallSiteSplitting.cpp File Reference
#include "llvm/Transforms/Scalar/CallSiteSplitting.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"

Go to the source code of this file.

Macros

#define DEBUG_TYPE   "callsite-splitting"
 

Typedefs

using ConditionTy = std::pair< ICmpInst *, unsigned >
 
using ConditionsTy = SmallVector< ConditionTy, 2 >
 
using PredsWithCondsTy = SmallVector< std::pair< BasicBlock *, ConditionsTy >, 2 >
 

Functions

 STATISTIC (NumCallSiteSplit, "Number of call-site split")
 
static void addNonNullAttribute (CallBase &CB, Value *Op)
 
static void setConstantInArgument (CallBase &CB, Value *Op, Constant *ConstValue)
 
static bool isCondRelevantToAnyCallArgument (ICmpInst *Cmp, CallBase &CB)
 
static void recordCondition (CallBase &CB, BasicBlock *From, BasicBlock *To, ConditionsTy &Conditions)
 If From has a conditional jump to To, add the condition to Conditions, if it is relevant to any argument at CB.
 
static void recordConditions (CallBase &CB, BasicBlock *Pred, ConditionsTy &Conditions, BasicBlock *StopAt)
 Record ICmp conditions relevant to any argument in CB following Pred's single predecessors.
 
static void addConditions (CallBase &CB, const ConditionsTy &Conditions)
 
static SmallVector< BasicBlock *, 2 > getTwoPredecessors (BasicBlock *BB)
 
static bool canSplitCallSite (CallBase &CB, TargetTransformInfo &TTI)
 
static InstructioncloneInstForMustTail (Instruction *I, Instruction *Before, Value *V)
 
static void copyMustTailReturn (BasicBlock *SplitBB, Instruction *CI, Instruction *NewCI)
 Copy mandatory musttail return sequence that follows original CI, and link it up to NewCI value instead:
 
static void splitCallSite (CallBase &CB, ArrayRef< std::pair< BasicBlock *, ConditionsTy > > Preds, DomTreeUpdater &DTU)
 For each (predecessor, conditions from predecessors) pair, it will split the basic block containing the call site, hook it up to the predecessor and replace the call instruction with new call instructions, which contain constraints based on the conditions from their predecessors.
 
static bool isPredicatedOnPHI (CallBase &CB)
 
static PredsWithCondsTy shouldSplitOnPHIPredicatedArgument (CallBase &CB)
 
static PredsWithCondsTy shouldSplitOnPredicatedArgument (CallBase &CB, DomTreeUpdater &DTU)
 
static bool tryToSplitCallSite (CallBase &CB, TargetTransformInfo &TTI, DomTreeUpdater &DTU)
 
static bool doCallSiteSplitting (Function &F, TargetLibraryInfo &TLI, TargetTransformInfo &TTI, DominatorTree &DT)
 

Variables

static cl::opt< unsignedDuplicationThreshold ("callsite-splitting-duplication-threshold", cl::Hidden, cl::desc("Only allow instructions before a call, if " "their cost is below DuplicationThreshold"), cl::init(5))
 Only allow instructions before a call, if their CodeSize cost is below DuplicationThreshold.
 

Macro Definition Documentation

◆ DEBUG_TYPE

#define DEBUG_TYPE   "callsite-splitting"

Definition at line 73 of file CallSiteSplitting.cpp.

Typedef Documentation

◆ ConditionsTy

using ConditionsTy = SmallVector<ConditionTy, 2>

Definition at line 125 of file CallSiteSplitting.cpp.

◆ ConditionTy

using ConditionTy = std::pair<ICmpInst *, unsigned>

Definition at line 124 of file CallSiteSplitting.cpp.

◆ PredsWithCondsTy

Definition at line 439 of file CallSiteSplitting.cpp.

Function Documentation

◆ addConditions()

static void addConditions ( CallBase CB,
const ConditionsTy Conditions 
)
static

◆ addNonNullAttribute()

static void addNonNullAttribute ( CallBase CB,
Value Op 
)
static

Definition at line 86 of file CallSiteSplitting.cpp.

References llvm::CallBase::addParamAttr(), llvm::CallBase::args(), and I.

Referenced by addConditions().

◆ canSplitCallSite()

static bool canSplitCallSite ( CallBase CB,
TargetTransformInfo TTI 
)
static

◆ cloneInstForMustTail()

static Instruction * cloneInstForMustTail ( Instruction I,
Instruction Before,
Value V 
)
static

Definition at line 221 of file CallSiteSplitting.cpp.

References Before, and I.

Referenced by copyMustTailReturn().

◆ copyMustTailReturn()

static void copyMustTailReturn ( BasicBlock SplitBB,
Instruction CI,
Instruction NewCI 
)
static

Copy mandatory musttail return sequence that follows original CI, and link it up to NewCI value instead:

  • (optional) bitcast NewCI to ...
  • ret bitcast or NewCI

Insert this sequence right before SplitBB's terminator, which will be cleaned up later in splitCallSite below.

Definition at line 239 of file CallSiteSplitting.cpp.

References assert(), cloneInstForMustTail(), llvm::ilist_node_impl< OptionsT >::getIterator(), llvm::BasicBlock::getParent(), llvm::Function::getReturnType(), llvm::BasicBlock::getTerminator(), and llvm::Type::isVoidTy().

Referenced by splitCallSite().

◆ doCallSiteSplitting()

static bool doCallSiteSplitting ( Function F,
TargetLibraryInfo TLI,
TargetTransformInfo TTI,
DominatorTree DT 
)
static

◆ getTwoPredecessors()

static SmallVector< BasicBlock *, 2 > getTwoPredecessors ( BasicBlock BB)
static

◆ isCondRelevantToAnyCallArgument()

static bool isCondRelevantToAnyCallArgument ( ICmpInst Cmp,
CallBase CB 
)
static

◆ isPredicatedOnPHI()

static bool isPredicatedOnPHI ( CallBase CB)
static

◆ recordCondition()

static void recordCondition ( CallBase CB,
BasicBlock From,
BasicBlock To,
ConditionsTy Conditions 
)
static

If From has a conditional jump to To, add the condition to Conditions, if it is relevant to any argument at CB.

Definition at line 129 of file CallSiteSplitting.cpp.

References Cond, From, isCondRelevantToAnyCallArgument(), llvm::PatternMatch::m_Constant(), llvm::PatternMatch::m_ICmp(), llvm::PatternMatch::m_Value(), llvm::PatternMatch::match(), and llvm::SmallVectorTemplateBase< T, bool >::push_back().

Referenced by recordConditions(), and shouldSplitOnPredicatedArgument().

◆ recordConditions()

static void recordConditions ( CallBase CB,
BasicBlock Pred,
ConditionsTy Conditions,
BasicBlock StopAt 
)
static

Record ICmp conditions relevant to any argument in CB following Pred's single predecessors.

If there are conflicting conditions along a path, like x == 1 and x == 0, the first condition will be used. We stop once we reach an edge to StopAt.

Definition at line 152 of file CallSiteSplitting.cpp.

References llvm::SmallPtrSetImpl< PtrType >::count(), From, llvm::SmallPtrSetImpl< PtrType >::insert(), and recordCondition().

Referenced by shouldSplitOnPredicatedArgument().

◆ setConstantInArgument()

static void setConstantInArgument ( CallBase CB,
Value Op,
Constant ConstValue 
)
static

◆ shouldSplitOnPHIPredicatedArgument()

static PredsWithCondsTy shouldSplitOnPHIPredicatedArgument ( CallBase CB)
static

◆ shouldSplitOnPredicatedArgument()

static PredsWithCondsTy shouldSplitOnPredicatedArgument ( CallBase CB,
DomTreeUpdater DTU 
)
static

◆ splitCallSite()

static void splitCallSite ( CallBase CB,
ArrayRef< std::pair< BasicBlock *, ConditionsTy > >  Preds,
DomTreeUpdater DTU 
)
static

For each (predecessor, conditions from predecessors) pair, it will split the basic block containing the call site, hook it up to the predecessor and replace the call instruction with new call instructions, which contain constraints based on the conditions from their predecessors.

For example, in the IR below with an OR condition, the call-site can be split. In this case, Preds for Tail is [(Header, a == null), (TBB, a != null, b == null)]. Tail is replaced by 2 split blocks, containing CallInst1, which has constraints based on the conditions from Head and CallInst2, which has constraints based on the conditions coming from TBB.

From :

Header: c = icmp eq i32* a, null br i1 c Tail, TBB TBB: c2 = icmp eq i32* b, null br i1 c Tail, End Tail: ca = call i1 @callee (i32* a, i32* b)

to :

Header: // PredBB1 is Header c = icmp eq i32* a, null br i1 c Tail-split1, TBB TBB: // PredBB2 is TBB c2 = icmp eq i32* b, null br i1 c Tail-split2, End Tail-split1: ca1 = call @callee (i32* null, i32* b) // CallInst1 br Tail Tail-split2: ca2 = call @callee (i32* nonnull a, i32* null) // CallInst2 br Tail Tail: p = phi i1 [ca1, Tail-split1],[ca2, Tail-split2]

Note that in case any arguments at the call-site are constrained by its predecessors, new call-sites with more constrained arguments will be created in createCallSitesOnPredicatedArgument().

Definition at line 302 of file CallSiteSplitting.cpp.

References addConditions(), llvm::PHINode::addIncoming(), llvm::DomTreeUpdater::applyUpdatesPermissive(), llvm::CallBase::args(), assert(), llvm::BasicBlock::begin(), copyMustTailReturn(), llvm::PHINode::Create(), llvm::dbgs(), llvm::DomTreeUpdater::deleteBB(), llvm::Instruction::dropDbgValues(), llvm::DuplicateInstructionsInSplitBetween(), llvm::Instruction::eraseFromParent(), llvm::Instruction::getDebugLoc(), llvm::ilist_node_impl< OptionsT >::getIterator(), llvm::Value::getName(), llvm::Instruction::getParent(), getParent(), llvm::ilist_node_impl< OptionsT >::getReverseIterator(), llvm::BasicBlock::getTerminator(), llvm::Value::getType(), I, llvm::Instruction::insertBefore(), llvm::CallBase::isMustTailCall(), LLVM_DEBUG, llvm::BasicBlock::phis(), llvm::predecessors(), llvm::BasicBlock::rend(), llvm::Value::replaceAllUsesWith(), llvm::Instruction::setDebugLoc(), llvm::SmallVectorBase< Size_T >::size(), llvm::SplitBlock(), and llvm::Value::use_empty().

Referenced by tryToSplitCallSite().

◆ STATISTIC()

STATISTIC ( NumCallSiteSplit  ,
"Number of call-site split"   
)

◆ tryToSplitCallSite()

static bool tryToSplitCallSite ( CallBase CB,
TargetTransformInfo TTI,
DomTreeUpdater DTU 
)
static

Variable Documentation

◆ DuplicationThreshold

cl::opt< unsigned > DuplicationThreshold("callsite-splitting-duplication-threshold", cl::Hidden, cl::desc("Only allow instructions before a call, if " "their cost is below DuplicationThreshold"), cl::init(5)) ( "callsite-splitting-duplication-threshold"  ,
cl::Hidden  ,
cl::desc("Only allow instructions before a call, if " "their cost is below DuplicationThreshold")  ,
cl::init(5)   
)
static

Only allow instructions before a call, if their CodeSize cost is below DuplicationThreshold.

Those instructions need to be duplicated in all split blocks.

Referenced by canSplitCallSite().