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//===- SimplifyHalfPowrLibCalls.cpp - Optimize specific half_powr calls ---===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a simple pass that applies an experimental
// transformation on calls to specific functions.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "simplify-libcalls-halfpowr"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Target/TargetData.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
namespace {
/// This pass optimizes well half_powr function calls.
///
class SimplifyHalfPowrLibCalls : public FunctionPass {
const TargetData *TD;
public:
static char ID; // Pass identification
SimplifyHalfPowrLibCalls() : FunctionPass(&ID) {}
bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
}
Instruction *
InlineHalfPowrs(const std::vector<Instruction *> &HalfPowrs,
Instruction *InsertPt);
};
char SimplifyHalfPowrLibCalls::ID = 0;
} // end anonymous namespace.
INITIALIZE_PASS(SimplifyHalfPowrLibCalls, "simplify-libcalls-halfpowr",
"Simplify half_powr library calls", false, false);
// Public interface to the Simplify HalfPowr LibCalls pass.
FunctionPass *llvm::createSimplifyHalfPowrLibCallsPass() {
return new SimplifyHalfPowrLibCalls();
}
/// InlineHalfPowrs - Inline a sequence of adjacent half_powr calls, rearranging
/// their control flow to better facilitate subsequent optimization.
Instruction *
SimplifyHalfPowrLibCalls::
InlineHalfPowrs(const std::vector<Instruction *> &HalfPowrs,
Instruction *InsertPt) {
std::vector<BasicBlock *> Bodies;
BasicBlock *NewBlock = 0;
for (unsigned i = 0, e = HalfPowrs.size(); i != e; ++i) {
CallInst *Call = cast<CallInst>(HalfPowrs[i]);
Function *Callee = Call->getCalledFunction();
// Minimally sanity-check the CFG of half_powr to ensure that it contains
// the kind of code we expect. If we're running this pass, we have
// reason to believe it will be what we expect.
Function::iterator I = Callee->begin();
BasicBlock *Prologue = I++;
if (I == Callee->end()) break;
BasicBlock *SubnormalHandling = I++;
if (I == Callee->end()) break;
BasicBlock *Body = I++;
if (I != Callee->end()) break;
if (SubnormalHandling->getSinglePredecessor() != Prologue)
break;
BranchInst *PBI = dyn_cast<BranchInst>(Prologue->getTerminator());
if (!PBI || !PBI->isConditional())
break;
BranchInst *SNBI = dyn_cast<BranchInst>(SubnormalHandling->getTerminator());
if (!SNBI || SNBI->isConditional())
break;
if (!isa<ReturnInst>(Body->getTerminator()))
break;
Instruction *NextInst = llvm::next(BasicBlock::iterator(Call));
// Inline the call, taking care of what code ends up where.
NewBlock = SplitBlock(NextInst->getParent(), NextInst, this);
InlineFunctionInfo IFI(0, TD);
bool B = InlineFunction(Call, IFI);
assert(B && "half_powr didn't inline?"); B=B;
BasicBlock *NewBody = NewBlock->getSinglePredecessor();
assert(NewBody);
Bodies.push_back(NewBody);
}
if (!NewBlock)
return InsertPt;
// Put the code for all the bodies into one block, to facilitate
// subsequent optimization.
(void)SplitEdge(NewBlock->getSinglePredecessor(), NewBlock, this);
for (unsigned i = 0, e = Bodies.size(); i != e; ++i) {
BasicBlock *Body = Bodies[i];
Instruction *FNP = Body->getFirstNonPHI();
// Splice the insts from body into NewBlock.
NewBlock->getInstList().splice(NewBlock->begin(), Body->getInstList(),
FNP, Body->getTerminator());
}
return NewBlock->begin();
}
/// runOnFunction - Top level algorithm.
///
bool SimplifyHalfPowrLibCalls::runOnFunction(Function &F) {
TD = getAnalysisIfAvailable<TargetData>();
bool Changed = false;
std::vector<Instruction *> HalfPowrs;
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
// Look for calls.
bool IsHalfPowr = false;
if (CallInst *CI = dyn_cast<CallInst>(I)) {
// Look for direct calls and calls to non-external functions.
Function *Callee = CI->getCalledFunction();
if (Callee && Callee->hasExternalLinkage()) {
// Look for calls with well-known names.
if (Callee->getName() == "__half_powrf4")
IsHalfPowr = true;
}
}
if (IsHalfPowr)
HalfPowrs.push_back(I);
// We're looking for sequences of up to three such calls, which we'll
// simplify as a group.
if ((!IsHalfPowr && !HalfPowrs.empty()) || HalfPowrs.size() == 3) {
I = InlineHalfPowrs(HalfPowrs, I);
E = I->getParent()->end();
HalfPowrs.clear();
Changed = true;
}
}
assert(HalfPowrs.empty() && "Block had no terminator!");
}
return Changed;
}
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