Reg2Mem cleanup and optimizations:
- enable phi instructions demotion to stack
- create alloca instructions in the entry block
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43208 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/Reg2Mem.cpp b/lib/Transforms/Scalar/Reg2Mem.cpp
index ef7411a..e4ef5ba 100644
--- a/lib/Transforms/Scalar/Reg2Mem.cpp
+++ b/lib/Transforms/Scalar/Reg2Mem.cpp
@@ -26,10 +26,12 @@
#include "llvm/Instructions.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/Support/CFG.h"
#include <list>
using namespace llvm;
-STATISTIC(NumDemoted, "Number of registers demoted");
+STATISTIC(NumRegsDemoted, "Number of registers demoted");
+STATISTIC(NumPhisDemoted, "Number of phi-nodes demoted");
namespace {
struct VISIBILITY_HIDDEN RegToMem : public FunctionPass {
@@ -43,8 +45,8 @@
bool valueEscapes(Instruction* i) {
BasicBlock* bb = i->getParent();
- for(Value::use_iterator ii = i->use_begin(), ie = i->use_end();
- ii != ie; ++ii)
+ for (Value::use_iterator ii = i->use_begin(), ie = i->use_end();
+ ii != ie; ++ii)
if (cast<Instruction>(*ii)->getParent() != bb ||
isa<PHINode>(*ii))
return true;
@@ -53,26 +55,57 @@
virtual bool runOnFunction(Function &F) {
if (!F.isDeclaration()) {
- //give us a clean block
- BasicBlock* bbold = &F.getEntryBlock();
- BasicBlock* bbnew = new BasicBlock("allocablock", &F,
- &F.getEntryBlock());
- new BranchInst(bbold, bbnew);
+ // Insert all new allocas into entry block.
+ BasicBlock* BBEntry = &F.getEntryBlock();
+ assert(pred_begin(BBEntry) == pred_end(BBEntry) &&
+ "Entry block to function must not have predecessors!");
- //find the instructions
+ // Find first non-alloca instruction and create insertion point. This is
+ // safe if block is well-formed: it always have terminator, otherwise
+ // we'll get and assertion.
+ BasicBlock::iterator I = BBEntry->begin();
+ while (isa<AllocaInst>(I)) ++I;
+
+ CastInst *AllocaInsertionPoint =
+ CastInst::create(Instruction::BitCast,
+ Constant::getNullValue(Type::Int32Ty), Type::Int32Ty,
+ "reg2mem alloca point", I);
+
+ // Find the escaped instructions. But don't create stack slots for
+ // allocas in entry block.
std::list<Instruction*> worklist;
for (Function::iterator ibb = F.begin(), ibe = F.end();
ibb != ibe; ++ibb)
for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
iib != iie; ++iib) {
- if(valueEscapes(iib))
+ if (!(isa<AllocaInst>(iib) && iib->getParent() == BBEntry) &&
+ valueEscapes(iib)) {
worklist.push_front(&*iib);
+ }
}
- //demote escaped instructions
- NumDemoted += worklist.size();
+
+ // Demote escaped instructions
+ NumRegsDemoted += worklist.size();
for (std::list<Instruction*>::iterator ilb = worklist.begin(),
ile = worklist.end(); ilb != ile; ++ilb)
- DemoteRegToStack(**ilb, false);
+ DemoteRegToStack(**ilb, false, AllocaInsertionPoint);
+
+ worklist.clear();
+
+ // Find all phi's
+ for (Function::iterator ibb = F.begin(), ibe = F.end();
+ ibb != ibe; ++ibb)
+ for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
+ iib != iie; ++iib)
+ if (isa<PHINode>(iib))
+ worklist.push_front(&*iib);
+
+ // Demote phi nodes
+ NumPhisDemoted += worklist.size();
+ for (std::list<Instruction*>::iterator ilb = worklist.begin(),
+ ile = worklist.end(); ilb != ile; ++ilb)
+ DemotePHIToStack(cast<PHINode>(*ilb), AllocaInsertionPoint);
+
return true;
}
return false;