1 //===- SimplifyHalfPowrLibCalls.cpp - Optimize specific half_powr calls ---===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements a simple pass that applies an experimental
11 // transformation on calls to specific functions.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "simplify-libcalls-halfpowr"
16 #include "llvm/Transforms/Scalar.h"
17 #include "llvm/Instructions.h"
18 #include "llvm/Intrinsics.h"
19 #include "llvm/Module.h"
20 #include "llvm/Pass.h"
21 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
22 #include "llvm/Transforms/Utils/Cloning.h"
23 #include "llvm/Target/TargetData.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include "llvm/Support/Debug.h"
29 /// This pass optimizes well half_powr function calls.
31 class SimplifyHalfPowrLibCalls : public FunctionPass {
34 static char ID; // Pass identification
35 SimplifyHalfPowrLibCalls() : FunctionPass(ID) {}
37 bool runOnFunction(Function &F);
39 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
43 InlineHalfPowrs(const std::vector<Instruction *> &HalfPowrs,
44 Instruction *InsertPt);
46 char SimplifyHalfPowrLibCalls::ID = 0;
47 } // end anonymous namespace.
49 INITIALIZE_PASS(SimplifyHalfPowrLibCalls, "simplify-libcalls-halfpowr",
50 "Simplify half_powr library calls", false, false);
52 // Public interface to the Simplify HalfPowr LibCalls pass.
53 FunctionPass *llvm::createSimplifyHalfPowrLibCallsPass() {
54 return new SimplifyHalfPowrLibCalls();
57 /// InlineHalfPowrs - Inline a sequence of adjacent half_powr calls, rearranging
58 /// their control flow to better facilitate subsequent optimization.
60 SimplifyHalfPowrLibCalls::
61 InlineHalfPowrs(const std::vector<Instruction *> &HalfPowrs,
62 Instruction *InsertPt) {
63 std::vector<BasicBlock *> Bodies;
64 BasicBlock *NewBlock = 0;
66 for (unsigned i = 0, e = HalfPowrs.size(); i != e; ++i) {
67 CallInst *Call = cast<CallInst>(HalfPowrs[i]);
68 Function *Callee = Call->getCalledFunction();
70 // Minimally sanity-check the CFG of half_powr to ensure that it contains
71 // the kind of code we expect. If we're running this pass, we have
72 // reason to believe it will be what we expect.
73 Function::iterator I = Callee->begin();
74 BasicBlock *Prologue = I++;
75 if (I == Callee->end()) break;
76 BasicBlock *SubnormalHandling = I++;
77 if (I == Callee->end()) break;
78 BasicBlock *Body = I++;
79 if (I != Callee->end()) break;
80 if (SubnormalHandling->getSinglePredecessor() != Prologue)
82 BranchInst *PBI = dyn_cast<BranchInst>(Prologue->getTerminator());
83 if (!PBI || !PBI->isConditional())
85 BranchInst *SNBI = dyn_cast<BranchInst>(SubnormalHandling->getTerminator());
86 if (!SNBI || SNBI->isConditional())
88 if (!isa<ReturnInst>(Body->getTerminator()))
91 Instruction *NextInst = llvm::next(BasicBlock::iterator(Call));
93 // Inline the call, taking care of what code ends up where.
94 NewBlock = SplitBlock(NextInst->getParent(), NextInst, this);
96 InlineFunctionInfo IFI(0, TD);
97 bool B = InlineFunction(Call, IFI);
98 assert(B && "half_powr didn't inline?"); B=B;
100 BasicBlock *NewBody = NewBlock->getSinglePredecessor();
102 Bodies.push_back(NewBody);
108 // Put the code for all the bodies into one block, to facilitate
109 // subsequent optimization.
110 (void)SplitEdge(NewBlock->getSinglePredecessor(), NewBlock, this);
111 for (unsigned i = 0, e = Bodies.size(); i != e; ++i) {
112 BasicBlock *Body = Bodies[i];
113 Instruction *FNP = Body->getFirstNonPHI();
114 // Splice the insts from body into NewBlock.
115 NewBlock->getInstList().splice(NewBlock->begin(), Body->getInstList(),
116 FNP, Body->getTerminator());
119 return NewBlock->begin();
122 /// runOnFunction - Top level algorithm.
124 bool SimplifyHalfPowrLibCalls::runOnFunction(Function &F) {
125 TD = getAnalysisIfAvailable<TargetData>();
127 bool Changed = false;
128 std::vector<Instruction *> HalfPowrs;
129 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
130 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
132 bool IsHalfPowr = false;
133 if (CallInst *CI = dyn_cast<CallInst>(I)) {
134 // Look for direct calls and calls to non-external functions.
135 Function *Callee = CI->getCalledFunction();
136 if (Callee && Callee->hasExternalLinkage()) {
137 // Look for calls with well-known names.
138 if (Callee->getName() == "__half_powrf4")
143 HalfPowrs.push_back(I);
144 // We're looking for sequences of up to three such calls, which we'll
145 // simplify as a group.
146 if ((!IsHalfPowr && !HalfPowrs.empty()) || HalfPowrs.size() == 3) {
147 I = InlineHalfPowrs(HalfPowrs, I);
148 E = I->getParent()->end();
153 assert(HalfPowrs.empty() && "Block had no terminator!");