#define DEBUG_TYPE "ipconstprop"
#include "llvm/Transforms/IPO.h"
-#include "llvm/Constants.h"
-#include "llvm/Instructions.h"
-#include "llvm/Module.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/CallSite.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/CallSite.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
using namespace llvm;
STATISTIC(NumArgumentsProped, "Number of args turned into constants");
namespace {
/// IPCP - The interprocedural constant propagation pass
///
- struct VISIBILITY_HIDDEN IPCP : public ModulePass {
+ struct IPCP : public ModulePass {
static char ID; // Pass identification, replacement for typeid
- IPCP() : ModulePass((intptr_t)&ID) {}
+ IPCP() : ModulePass(ID) {
+ initializeIPCPPass(*PassRegistry::getPassRegistry());
+ }
- bool runOnModule(Module &M);
+ bool runOnModule(Module &M) override;
private:
bool PropagateConstantsIntoArguments(Function &F);
bool PropagateConstantReturn(Function &F);
};
- char IPCP::ID = 0;
- RegisterPass<IPCP> X("ipconstprop", "Interprocedural constant propagation");
}
+char IPCP::ID = 0;
+INITIALIZE_PASS(IPCP, "ipconstprop",
+ "Interprocedural constant propagation", false, false)
+
ModulePass *llvm::createIPConstantPropagationPass() { return new IPCP(); }
bool IPCP::runOnModule(Module &M) {
if (!I->isDeclaration()) {
// Delete any klingons.
I->removeDeadConstantUsers();
- if (I->hasInternalLinkage())
+ if (I->hasLocalLinkage())
LocalChange |= PropagateConstantsIntoArguments(*I);
Changed |= PropagateConstantReturn(*I);
}
ArgumentConstants.resize(F.arg_size());
unsigned NumNonconstant = 0;
- for (Value::use_iterator UI = F.use_begin(), E = F.use_end(); UI != E; ++UI) {
+ for (Use &U : F.uses()) {
+ User *UR = U.getUser();
+ // Ignore blockaddress uses.
+ if (isa<BlockAddress>(UR)) continue;
+
// Used by a non-instruction, or not the callee of a function, do not
// transform.
- if (UI.getOperandNo() != 0 ||
- (!isa<CallInst>(*UI) && !isa<InvokeInst>(*UI)))
+ if (!isa<CallInst>(UR) && !isa<InvokeInst>(UR))
return false;
- CallSite CS = CallSite::get(cast<Instruction>(*UI));
+ CallSite CS(cast<Instruction>(UR));
+ if (!CS.isCallee(&U))
+ return false;
// Check out all of the potentially constant arguments. Note that we don't
// inspect varargs here.
Function::arg_iterator AI = F.arg_begin();
for (unsigned i = 0, e = ArgumentConstants.size(); i != e; ++i, ++AI) {
// Do we have a constant argument?
- if (ArgumentConstants[i].second || AI->use_empty())
+ if (ArgumentConstants[i].second || AI->use_empty() ||
+ AI->hasInAllocaAttr() || (AI->hasByValAttr() && !F.onlyReadsMemory()))
continue;
Value *V = ArgumentConstants[i].first;
}
-// Check to see if this function returns a constant. If so, replace all callers
-// that user the return value with the returned valued. If we can replace ALL
-// callers,
+// Check to see if this function returns one or more constants. If so, replace
+// all callers that use those return values with the constant value. This will
+// leave in the actual return values and instructions, but deadargelim will
+// clean that up.
+//
+// Additionally if a function always returns one of its arguments directly,
+// callers will be updated to use the value they pass in directly instead of
+// using the return value.
bool IPCP::PropagateConstantReturn(Function &F) {
- if (F.getReturnType() == Type::VoidTy)
+ if (F.getReturnType()->isVoidTy())
return false; // No return value.
+ // If this function could be overridden later in the link stage, we can't
+ // propagate information about its results into callers.
+ if (F.mayBeOverridden())
+ return false;
+
// Check to see if this function returns a constant.
SmallVector<Value *,4> RetVals;
- const StructType *STy = dyn_cast<StructType>(F.getReturnType());
+ StructType *STy = dyn_cast<StructType>(F.getReturnType());
if (STy)
- RetVals.assign(STy->getNumElements(), 0);
+ for (unsigned i = 0, e = STy->getNumElements(); i < e; ++i)
+ RetVals.push_back(UndefValue::get(STy->getElementType(i)));
else
- RetVals.push_back(0);
+ RetVals.push_back(UndefValue::get(F.getReturnType()));
+ unsigned NumNonConstant = 0;
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
- assert(RetVals.size() == RI->getNumOperands() &&
- "Invalid ReturnInst operands!");
for (unsigned i = 0, e = RetVals.size(); i != e; ++i) {
- if (isa<UndefValue>(RI->getOperand(i)))
- continue; // Ignore
- Constant *C = dyn_cast<Constant>(RI->getOperand(i));
- if (C == 0)
- return false; // Does not return a constant.
-
+ // Already found conflicting return values?
Value *RV = RetVals[i];
- if (RV == 0)
- RetVals[i] = C;
- else if (RV != C)
- return false; // Does not return the same constant.
+ if (!RV)
+ continue;
+
+ // Find the returned value
+ Value *V;
+ if (!STy)
+ V = RI->getOperand(0);
+ else
+ V = FindInsertedValue(RI->getOperand(0), i);
+
+ if (V) {
+ // Ignore undefs, we can change them into anything
+ if (isa<UndefValue>(V))
+ continue;
+
+ // Try to see if all the rets return the same constant or argument.
+ if (isa<Constant>(V) || isa<Argument>(V)) {
+ if (isa<UndefValue>(RV)) {
+ // No value found yet? Try the current one.
+ RetVals[i] = V;
+ continue;
+ }
+ // Returning the same value? Good.
+ if (RV == V)
+ continue;
+ }
+ }
+ // Different or no known return value? Don't propagate this return
+ // value.
+ RetVals[i] = 0;
+ // All values non-constant? Stop looking.
+ if (++NumNonConstant == RetVals.size())
+ return false;
}
}
- if (STy) {
- for (unsigned i = 0, e = RetVals.size(); i < e; ++i)
- if (RetVals[i] == 0)
- RetVals[i] = UndefValue::get(STy->getElementType(i));
- } else {
- assert(RetVals.size() == 1);
- if (RetVals[0] == 0)
- RetVals[0] = UndefValue::get(F.getReturnType());
- }
-
- // If we got here, the function returns a constant value. Loop over all
- // users, replacing any uses of the return value with the returned constant.
- bool ReplacedAllUsers = true;
+ // If we got here, the function returns at least one constant value. Loop
+ // over all users, replacing any uses of the return value with the returned
+ // constant.
bool MadeChange = false;
- for (Value::use_iterator UI = F.use_begin(), E = F.use_end(); UI != E; ++UI) {
- // Make sure this is an invoke or call and that the use is for the callee.
- if (!(isa<InvokeInst>(*UI) || isa<CallInst>(*UI)) ||
- UI.getOperandNo() != 0) {
- ReplacedAllUsers = false;
+ for (Use &U : F.uses()) {
+ CallSite CS(U.getUser());
+ Instruction* Call = CS.getInstruction();
+
+ // Not a call instruction or a call instruction that's not calling F
+ // directly?
+ if (!Call || !CS.isCallee(&U))
continue;
- }
- Instruction *Call = cast<Instruction>(*UI);
+ // Call result not used?
if (Call->use_empty())
continue;
MadeChange = true;
if (STy == 0) {
- Call->replaceAllUsesWith(RetVals[0]);
+ Value* New = RetVals[0];
+ if (Argument *A = dyn_cast<Argument>(New))
+ // Was an argument returned? Then find the corresponding argument in
+ // the call instruction and use that.
+ New = CS.getArgument(A->getArgNo());
+ Call->replaceAllUsesWith(New);
continue;
}
-
- while (!Call->use_empty()) {
- GetResultInst *GR = cast<GetResultInst>(Call->use_back());
- GR->replaceAllUsesWith(RetVals[GR->getIndex()]);
- GR->eraseFromParent();
- }
- }
-
- // If we replace all users with the returned constant, and there can be no
- // other callers of the function, replace the constant being returned in the
- // function with an undef value.
- if (ReplacedAllUsers && F.hasInternalLinkage()) {
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
- if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
- for (unsigned i = 0, e = RetVals.size(); i < e; ++i) {
- Value *RetVal = RetVals[i];
- if (isa<UndefValue>(RetVal))
- continue;
- Value *RV = UndefValue::get(RetVal->getType());
- if (RI->getOperand(i) != RV) {
- RI->setOperand(i, RV);
- MadeChange = true;
- }
+
+ for (auto I = Call->user_begin(), E = Call->user_end(); I != E;) {
+ Instruction *Ins = cast<Instruction>(*I);
+
+ // Increment now, so we can remove the use
+ ++I;
+
+ // Find the index of the retval to replace with
+ int index = -1;
+ if (ExtractValueInst *EV = dyn_cast<ExtractValueInst>(Ins))
+ if (EV->hasIndices())
+ index = *EV->idx_begin();
+
+ // If this use uses a specific return value, and we have a replacement,
+ // replace it.
+ if (index != -1) {
+ Value *New = RetVals[index];
+ if (New) {
+ if (Argument *A = dyn_cast<Argument>(New))
+ // Was an argument returned? Then find the corresponding argument in
+ // the call instruction and use that.
+ New = CS.getArgument(A->getArgNo());
+ Ins->replaceAllUsesWith(New);
+ Ins->eraseFromParent();
}
}
}
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