6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-09-30 19:55:11 +00:00
Code Issues Projects Releases Wiki Activity

Rewrite CorrectExtraCFGEdges() to make it more understandable.

Browse Source 
* Set the "DestA" and "DestB" according to how they're understood by the
  method. I.e., if one or both of them should point to the "fall through" block,
  then point to the fall through block.

* Improve the loop that removes superfluous edges to be more understandable.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100056 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2010-03-31 22:54:38 +00:00
parent 368454976c
commit bbd51cd0a1
1 changed files with 23 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
lib/CodeGen/MachineBasicBlock.cpp
View File

@ -23,6 +23,7 @@
#include "llvm/Target/TargetMachine.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/LeakDetector.h"
#include "llvm/Support/raw_ostream.h"
@ -459,54 +460,41 @@ bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
// conditional branch followed by an unconditional branch. DestA is the
// 'true' destination and DestB is the 'false' destination.
bool MadeChange = false;
bool AddedFallThrough = false;
bool Changed = false;
MachineFunction::iterator FallThru =
llvm::next(MachineFunction::iterator(this));
if (isCond) {
// If this block ends with a conditional branch that falls through to its
// successor, set DestB as the successor.
if (DestB == 0 && FallThru != getParent()->end()) {
if (DestA == 0 && DestB == 0) {
// Block falls through to successor.
DestA = FallThru;
DestB = FallThru;
} else if (DestA != 0 && DestB == 0) {
if (isCond)
// Block ends in conditional jump that falls through to successor.
DestB = FallThru;
AddedFallThrough = true;
}
} else {
// If this is an unconditional branch with no explicit dest, it must just be
// a fallthrough into DestA.
if (DestA == 0 && FallThru != getParent()->end()) {
DestA = FallThru;
AddedFallThrough = true;
}
assert(DestA && DestB && isCond &&
"CFG in a bad state. Cannot correct CFG edges");
}
// Remove superfluous edges. I.e., those which aren't destinations of this
// basic block, duplicate edges, or landing pads.
SmallPtrSet<const MachineBasicBlock*, 8> SeenMBBs;
MachineBasicBlock::succ_iterator SI = succ_begin();
MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB;
while (SI != succ_end()) {
const MachineBasicBlock *MBB = *SI;
if (MBB == DestA) {
DestA = 0;
++SI;
} else if (MBB == DestB) {
DestB = 0;
++SI;
} else if (MBB->isLandingPad() &&
MBB != OrigDestA && MBB != OrigDestB) {
++SI;
} else {
// Otherwise, this is a superfluous edge, remove it.
if (!SeenMBBs.insert(MBB) ||
(MBB != DestA && MBB != DestB && !MBB->isLandingPad())) {
// This is a superfluous edge, remove it.
SI = removeSuccessor(SI);
MadeChange = true;
Changed = true;
} else {
++SI;
}
}
if (!AddedFallThrough)
assert(DestA == 0 && DestB == 0 && "MachineCFG is missing edges!");
else if (isCond)
assert(DestA == 0 && "MachineCFG is missing edges!");
return MadeChange;
return Changed;
}
/// findDebugLoc - find the next valid DebugLoc starting at MBBI, skipping