mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2025-09-11 08:29:25 +00:00
a9d2bffeeb
in the old destination block to indicate that the value flows from the new edge splitting block, not from the original multi-successor block. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3590 91177308-0d34-0410-b5e6-96231b3b80d8
95 lines
3.7 KiB
C++
95 lines
3.7 KiB
C++
//===-- Local.h - Functions to perform local transformations -----*- C++ -*--=//
|
|
//
|
|
// This family of functions perform various local transformations to the
|
|
// program.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Transforms/Utils/Local.h"
|
|
#include "llvm/iTerminators.h"
|
|
#include "llvm/iPHINode.h"
|
|
#include "llvm/Analysis/Dominators.h"
|
|
#include "llvm/Support/CFG.h"
|
|
|
|
// isCriticalEdge - Return true if the specified edge is a critical edge.
|
|
// Critical edges are edges from a block with multiple successors to a block
|
|
// with multiple predecessors.
|
|
//
|
|
bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum) {
|
|
assert(SuccNum < TI->getNumSuccessors() && "Illegal edge specification!");
|
|
if (TI->getNumSuccessors() <= 1) return false;
|
|
|
|
const BasicBlock *Dest = TI->getSuccessor(SuccNum);
|
|
pred_const_iterator I = pred_begin(Dest), E = pred_end(Dest);
|
|
|
|
// If there is more than one predecessor, this is a critical edge...
|
|
assert(I != E && "No preds, but we have an edge to the block?");
|
|
++I; // Skip one edge due to the incoming arc from TI.
|
|
return I != E;
|
|
}
|
|
|
|
// SplitCriticalEdge - Insert a new node node to split the critical edge. This
|
|
// will update DominatorSet, ImmediateDominator and DominatorTree information if
|
|
// it is available, thus calling this pass will not invalidate either of them.
|
|
//
|
|
void SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
|
|
assert(isCriticalEdge(TI, SuccNum) &&
|
|
"Cannot break a critical edge, if it isn't a critical edge");
|
|
BasicBlock *TIBB = TI->getParent();
|
|
|
|
// Create a new basic block, linking it into the CFG.
|
|
BasicBlock *NewBB = new BasicBlock(TIBB->getName()+"_crit_edge");
|
|
BasicBlock *DestBB = TI->getSuccessor(SuccNum);
|
|
// Create our unconditional branch...
|
|
BranchInst *BI = new BranchInst(DestBB);
|
|
NewBB->getInstList().push_back(BI);
|
|
|
|
// Branch to the new block, breaking the edge...
|
|
TI->setSuccessor(SuccNum, NewBB);
|
|
|
|
// Insert the block into the function... right after the block TI lives in.
|
|
Function &F = *TIBB->getParent();
|
|
F.getBasicBlockList().insert(TIBB->getNext(), NewBB);
|
|
|
|
// If there are any PHI nodes in DestBB, we need to update them so that they
|
|
// merge incoming values from NewBB instead of from TIBB.
|
|
//
|
|
for (BasicBlock::iterator I = DestBB->begin();
|
|
PHINode *PN = dyn_cast<PHINode>(&*I); ++I) {
|
|
// We no longer enter through TIBB, now we come in through NewBB.
|
|
PN->replaceUsesOfWith(TIBB, NewBB);
|
|
}
|
|
|
|
// Now if we have a pass object, update analysis information. Currently we
|
|
// update DominatorSet and DominatorTree information if it's available.
|
|
//
|
|
if (P) {
|
|
// Should we update DominatorSet information?
|
|
if (DominatorSet *DS = P->getAnalysisToUpdate<DominatorSet>()) {
|
|
// The blocks that dominate the new one are the blocks that dominate TIBB
|
|
// plus the new block itself.
|
|
DominatorSet::DomSetType DomSet = DS->getDominators(TIBB);
|
|
DomSet.insert(NewBB); // A block always dominates itself.
|
|
DS->addBasicBlock(NewBB, DomSet);
|
|
}
|
|
|
|
// Should we update ImmdediateDominator information?
|
|
if (ImmediateDominators *ID =
|
|
P->getAnalysisToUpdate<ImmediateDominators>()) {
|
|
// TIBB is the new immediate dominator for NewBB. NewBB doesn't dominate
|
|
// anything.
|
|
ID->addNewBlock(NewBB, TIBB);
|
|
}
|
|
|
|
// Should we update DominatorTree information?
|
|
if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>()) {
|
|
DominatorTree::Node *TINode = DT->getNode(TIBB);
|
|
|
|
// The new block is not the immediate dominator for any other nodes, but
|
|
// TINode is the immediate dominator for the new node.
|
|
//
|
|
DT->createNewNode(NewBB, TINode);
|
|
}
|
|
}
|
|
}
|