Move CorrectExtraCFGEdges() from BranchFolding.cpp to a MachineBasicBlock method.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37633 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index af36764..da062b1 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -225,3 +225,63 @@
addSuccessor(New);
}
+/// CorrectExtraCFGEdges - Various pieces of code can cause excess edges in the
+/// CFG to be inserted. If we have proven that MBB can only branch to DestA and
+/// DestB, remove any other MBB successors from the CFG. DestA and DestB can
+/// be null.
+/// Besides DestA and DestB, retain other edges leading to LandingPads (currently
+/// there can be only one; we don't check or require that here).
+/// Note it is possible that DestA and/or DestB are LandingPads.
+bool MachineBasicBlock::CorrectExtraCFGEdges(MachineBasicBlock *DestA,
+ MachineBasicBlock *DestB,
+ bool isCond) {
+ bool MadeChange = false;
+ bool AddedFallThrough = false;
+
+ MachineBasicBlock *FallThru = getNext();
+
+ // If this block ends with a conditional branch that falls through to its
+ // successor, set DestB as the successor.
+ if (isCond) {
+ if (DestB == 0 && FallThru != getParent()->end()) {
+ DestB = FallThru;
+ AddedFallThrough = true;
+ }
+ } else {
+ // If this is an unconditional branch with no explicit dest, it must just be
+ // a fallthrough into DestB.
+ if (DestA == 0 && FallThru != getParent()->end()) {
+ DestA = FallThru;
+ AddedFallThrough = true;
+ }
+ }
+
+ MachineBasicBlock::succ_iterator SI = succ_begin();
+ MachineBasicBlock *OrigDestA = DestA, *OrigDestB = DestB;
+ while (SI != succ_end()) {
+ if (*SI == DestA && DestA == DestB) {
+ DestA = DestB = 0;
+ ++SI;
+ } else if (*SI == DestA) {
+ DestA = 0;
+ ++SI;
+ } else if (*SI == DestB) {
+ DestB = 0;
+ ++SI;
+ } else if ((*SI)->isLandingPad() &&
+ *SI!=OrigDestA && *SI!=OrigDestB) {
+ ++SI;
+ } else {
+ // Otherwise, this is a superfluous edge, remove it.
+ removeSuccessor(SI);
+ MadeChange = true;
+ }
+ }
+ if (!AddedFallThrough) {
+ assert(DestA == 0 && DestB == 0 &&
+ "MachineCFG is missing edges!");
+ } else if (isCond) {
+ assert(DestA == 0 && "MachineCFG is missing edges!");
+ }
+ return MadeChange;
+}