It's not necessary to do rounding for alloca operations when the requested
alignment is equal to the stack alignment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/IPConstantPropagation.cpp b/lib/Transforms/IPO/IPConstantPropagation.cpp
new file mode 100644
index 0000000..b55e538
--- /dev/null
+++ b/lib/Transforms/IPO/IPConstantPropagation.cpp
@@ -0,0 +1,197 @@
+//===-- IPConstantPropagation.cpp - Propagate constants through calls -----===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass implements an _extremely_ simple interprocedural constant
+// propagation pass. It could certainly be improved in many different ways,
+// like using a worklist. This pass makes arguments dead, but does not remove
+// them. The existing dead argument elimination pass should be run after this
+// to clean up the mess.
+//
+//===----------------------------------------------------------------------===//
+
+#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"
+using namespace llvm;
+
+STATISTIC(NumArgumentsProped, "Number of args turned into constants");
+STATISTIC(NumReturnValProped, "Number of return values turned into constants");
+
+namespace {
+ /// IPCP - The interprocedural constant propagation pass
+ ///
+ struct VISIBILITY_HIDDEN IPCP : public ModulePass {
+ static char ID; // Pass identification, replacement for typeid
+ IPCP() : ModulePass((intptr_t)&ID) {}
+
+ bool runOnModule(Module &M);
+ private:
+ bool PropagateConstantsIntoArguments(Function &F);
+ bool PropagateConstantReturn(Function &F);
+ };
+ char IPCP::ID = 0;
+ RegisterPass<IPCP> X("ipconstprop", "Interprocedural constant propagation");
+}
+
+ModulePass *llvm::createIPConstantPropagationPass() { return new IPCP(); }
+
+bool IPCP::runOnModule(Module &M) {
+ bool Changed = false;
+ bool LocalChange = true;
+
+ // FIXME: instead of using smart algorithms, we just iterate until we stop
+ // making changes.
+ while (LocalChange) {
+ LocalChange = false;
+ for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
+ if (!I->isDeclaration()) {
+ // Delete any klingons.
+ I->removeDeadConstantUsers();
+ if (I->hasInternalLinkage())
+ LocalChange |= PropagateConstantsIntoArguments(*I);
+ Changed |= PropagateConstantReturn(*I);
+ }
+ Changed |= LocalChange;
+ }
+ return Changed;
+}
+
+/// PropagateConstantsIntoArguments - Look at all uses of the specified
+/// function. If all uses are direct call sites, and all pass a particular
+/// constant in for an argument, propagate that constant in as the argument.
+///
+bool IPCP::PropagateConstantsIntoArguments(Function &F) {
+ if (F.arg_empty() || F.use_empty()) return false; // No arguments? Early exit.
+
+ std::vector<std::pair<Constant*, bool> > ArgumentConstants;
+ ArgumentConstants.resize(F.arg_size());
+
+ unsigned NumNonconstant = 0;
+
+ for (Value::use_iterator I = F.use_begin(), E = F.use_end(); I != E; ++I)
+ if (!isa<Instruction>(*I))
+ return false; // Used by a non-instruction, do not transform
+ else {
+ CallSite CS = CallSite::get(cast<Instruction>(*I));
+ if (CS.getInstruction() == 0 ||
+ CS.getCalledFunction() != &F)
+ return false; // Not a direct call site?
+
+ // Check out all of the potentially constant arguments
+ CallSite::arg_iterator AI = CS.arg_begin();
+ Function::arg_iterator Arg = F.arg_begin();
+ for (unsigned i = 0, e = ArgumentConstants.size(); i != e;
+ ++i, ++AI, ++Arg) {
+ if (*AI == &F) return false; // Passes the function into itself
+
+ if (!ArgumentConstants[i].second) {
+ if (Constant *C = dyn_cast<Constant>(*AI)) {
+ if (!ArgumentConstants[i].first)
+ ArgumentConstants[i].first = C;
+ else if (ArgumentConstants[i].first != C) {
+ // Became non-constant
+ ArgumentConstants[i].second = true;
+ ++NumNonconstant;
+ if (NumNonconstant == ArgumentConstants.size()) return false;
+ }
+ } else if (*AI != &*Arg) { // Ignore recursive calls with same arg
+ // This is not a constant argument. Mark the argument as
+ // non-constant.
+ ArgumentConstants[i].second = true;
+ ++NumNonconstant;
+ if (NumNonconstant == ArgumentConstants.size()) return false;
+ }
+ }
+ }
+ }
+
+ // If we got to this point, there is a constant argument!
+ assert(NumNonconstant != ArgumentConstants.size());
+ Function::arg_iterator AI = F.arg_begin();
+ bool MadeChange = false;
+ for (unsigned i = 0, e = ArgumentConstants.size(); i != e; ++i, ++AI)
+ // Do we have a constant argument!?
+ if (!ArgumentConstants[i].second && !AI->use_empty()) {
+ Value *V = ArgumentConstants[i].first;
+ if (V == 0) V = UndefValue::get(AI->getType());
+ AI->replaceAllUsesWith(V);
+ ++NumArgumentsProped;
+ MadeChange = true;
+ }
+ return MadeChange;
+}
+
+
+// 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,
+bool IPCP::PropagateConstantReturn(Function &F) {
+ if (F.getReturnType() == Type::VoidTy)
+ return false; // No return value.
+
+ // Check to see if this function returns a constant.
+ Value *RetVal = 0;
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+ if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
+ if (isa<UndefValue>(RI->getOperand(0))) {
+ // Ignore.
+ } else if (Constant *C = dyn_cast<Constant>(RI->getOperand(0))) {
+ if (RetVal == 0)
+ RetVal = C;
+ else if (RetVal != C)
+ return false; // Does not return the same constant.
+ } else {
+ return false; // Does not return a constant.
+ }
+
+ if (RetVal == 0) RetVal = 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;
+ bool MadeChange = false;
+ for (Value::use_iterator I = F.use_begin(), E = F.use_end(); I != E; ++I)
+ if (!isa<Instruction>(*I))
+ ReplacedAllUsers = false;
+ else {
+ CallSite CS = CallSite::get(cast<Instruction>(*I));
+ if (CS.getInstruction() == 0 ||
+ CS.getCalledFunction() != &F) {
+ ReplacedAllUsers = false;
+ } else {
+ if (!CS.getInstruction()->use_empty()) {
+ CS.getInstruction()->replaceAllUsesWith(RetVal);
+ MadeChange = true;
+ }
+ }
+ }
+
+ // 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() && !isa<UndefValue>(RetVal)) {
+ Value *RV = UndefValue::get(RetVal->getType());
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+ if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
+ if (RI->getOperand(0) != RV) {
+ RI->setOperand(0, RV);
+ MadeChange = true;
+ }
+ }
+ }
+
+ if (MadeChange) ++NumReturnValProped;
+ return MadeChange;
+}