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* Finegrainify namespacification

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* Make the cost metric for passing constants in as arguments to functions MUCH
  more accurate, by actually estimating the amount of code that will be constant
  propagated away.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10136 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2003-11-21 21:46:09 +00:00
parent a51bcb50b0
commit 869adc283c
1 changed files with 105 additions and 36 deletions
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141
lib/Transforms/IPO/InlineSimple.cpp
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@ -12,19 +12,26 @@
//===----------------------------------------------------------------------===//
#include "Inliner.h"
#include "llvm/Instructions.h"
#include "llvm/Function.h"
#include "llvm/iMemory.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Transforms/IPO.h"
namespace llvm {
using namespace llvm;
namespace {
// FunctionInfo - For each function, calculate the size of it in blocks and
// instructions.
struct FunctionInfo {
// NumInsts, NumBlocks - Keep track of how large each function is, which is
// used to estimate the code size cost of inlining it.
unsigned NumInsts, NumBlocks;
// ConstantArgumentWeights - Each formal argument of the function is
// inspected to see if it is used in any contexts where making it a constant
// would reduce the code size. If so, we add some value to the argument
// entry here.
std::vector<unsigned> ConstantArgumentWeights;
FunctionInfo() : NumInsts(0), NumBlocks(0) {}
};
@ -36,14 +43,57 @@ namespace {
RegisterOpt<SimpleInliner> X("inline", "Function Integration/Inlining");
}
Pass *createFunctionInliningPass() { return new SimpleInliner(); }
Pass *llvm::createFunctionInliningPass() { return new SimpleInliner(); }
// CountCodeReductionForConstant - Figure out an approximation for how many
// instructions will be constant folded if the specified value is constant.
//
static unsigned CountCodeReductionForConstant(Value *V) {
unsigned Reduction = 0;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
if (isa<BranchInst>(*UI))
Reduction += 40; // Eliminating a conditional branch is a big win
else if (SwitchInst *SI = dyn_cast<SwitchInst>(*UI))
// Eliminating a switch is a big win, proportional to the number of edges
// deleted.
Reduction += (SI->getNumSuccessors()-1) * 40;
else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
// Turning an indirect call into a direct call is a BIG win
Reduction += CI->getCalledValue() == V ? 500 : 0;
} else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
// Turning an indirect call into a direct call is a BIG win
Reduction += CI->getCalledValue() == V ? 500 : 0;
} else {
// Figure out if this instruction will be removed due to simple constant
// propagation.
Instruction &Inst = cast<Instruction>(**UI);
bool AllOperandsConstant = true;
for (unsigned i = 0, e = Inst.getNumOperands(); i != e; ++i)
if (!isa<Constant>(Inst.getOperand(i)) &&
!isa<GlobalValue>(Inst.getOperand(i)) && Inst.getOperand(i) != V) {
AllOperandsConstant = false;
break;
}
if (AllOperandsConstant) {
// We will get to remove this instruction...
Reduction += 7;
// And any other instructions that use it which become constants
// themselves.
Reduction += CountCodeReductionForConstant(&Inst);
}
}
return Reduction;
}
// getInlineCost - The heuristic used to determine if we should inline the
// function call or not.
//
int SimpleInliner::getInlineCost(CallSite CS) {
Instruction *TheCall = CS.getInstruction();
const Function *Callee = CS.getCalledFunction();
Function *Callee = CS.getCalledFunction();
const Function *Caller = TheCall->getParent()->getParent();
// Don't inline a directly recursive call.
@ -61,34 +111,7 @@ int SimpleInliner::getInlineCost(CallSite CS) {
if (Callee->hasInternalLinkage() && Callee->hasOneUse())
InlineCost -= 30000;
// Add to the inline quality for properties that make the call valuable to
// inline. This includes factors that indicate that the result of inlining
// the function will be optimizable. Currently this just looks at arguments
// passed into the function.
//
for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
I != E; ++I) {
// Each argument passed in has a cost at both the caller and the callee
// sides. This favors functions that take many arguments over functions
// that take few arguments.
InlineCost -= 20;
// If this is a function being passed in, it is very likely that we will be
// able to turn an indirect function call into a direct function call.
if (isa<Function>(I))
InlineCost -= 100;
// If a constant, global variable or alloca is passed in, inlining this
// function is likely to allow significant future optimization possibilities
// (constant propagation, scalar promotion, and scalarization), so encourage
// the inlining of the function.
//
else if (isa<Constant>(I) || isa<GlobalVariable>(I) || isa<AllocaInst>(I))
InlineCost -= 60;
}
// Now that we have considered all of the factors that make the call site more
// likely to be inlined, look at factors that make us not want to inline it.
// Get information about the callee...
FunctionInfo &CalleeFI = CachedFunctionInfo[Callee];
// If we haven't calculated this information yet...
@ -102,19 +125,65 @@ int SimpleInliner::getInlineCost(CallSite CS) {
NumInsts += BB->size();
NumBlocks++;
}
CalleeFI.NumBlocks = NumBlocks;
CalleeFI.NumInsts = NumInsts;
// Check out all of the arguments to the function, figuring out how much
// code can be eliminated if one of the arguments is a constant.
std::vector<unsigned> &ArgWeights = CalleeFI.ConstantArgumentWeights;
for (Function::aiterator I = Callee->abegin(), E = Callee->aend();
I != E; ++I)
ArgWeights.push_back(CountCodeReductionForConstant(I));
}
// Add to the inline quality for properties that make the call valuable to
// inline. This includes factors that indicate that the result of inlining
// the function will be optimizable. Currently this just looks at arguments
// passed into the function.
//
unsigned ArgNo = 0;
for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
I != E; ++I, ++ArgNo) {
// Each argument passed in has a cost at both the caller and the callee
// sides. This favors functions that take many arguments over functions
// that take few arguments.
InlineCost -= 20;
// If this is a function being passed in, it is very likely that we will be
// able to turn an indirect function call into a direct function call.
if (isa<Function>(I))
InlineCost -= 100;
// If an alloca is passed in, inlining this function is likely to allow
// significant future optimization possibilities (like scalar promotion, and
// scalarization), so encourage the inlining of the function.
//
else if (isa<AllocaInst>(I))
InlineCost -= 60;
// If this is a constant being passed into the function, use the argument
// weights calculated for the callee to determine how much will be folded
// away with this information.
else if (isa<Constant>(I) || isa<GlobalVariable>(I)) {
if (ArgNo < CalleeFI.ConstantArgumentWeights.size())
InlineCost -= CalleeFI.ConstantArgumentWeights[ArgNo];
}
}
// Now that we have considered all of the factors that make the call site more
// likely to be inlined, look at factors that make us not want to inline it.
// Don't inline into something too big, which would make it bigger. Here, we
// count each basic block as a single unit.
InlineCost += Caller->size()*2;
// Look at the size of the callee. Each basic block counts as 20 units, and
// each instruction counts as 10.
InlineCost += CalleeFI.NumInsts*10 + CalleeFI.NumBlocks*20;
// each instruction counts as 5.
InlineCost += CalleeFI.NumInsts*5 + CalleeFI.NumBlocks*20;
return InlineCost;
}
} // End llvm namespace