move isOnlyReachableByFallthrough out of MachineBasicBlock into AsmPrinter,
and add a sparc implementation that knows about delay slots. Patch by
Nathan Keynes!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96492 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index fc08384..9f905db 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1717,7 +1717,7 @@
}
// Print the main label for the block.
- if (MBB->pred_empty() || MBB->isOnlyReachableByFallthrough()) {
+ if (MBB->pred_empty() || isBlockOnlyReachableByFallthrough(MBB)) {
if (VerboseAsm) {
// NOTE: Want this comment at start of line.
O << MAI->getCommentString() << " BB#" << MBB->getNumber() << ':';
@@ -1764,6 +1764,39 @@
O << Offset;
}
+/// isBlockOnlyReachableByFallthough - Return true if the basic block has
+/// exactly one predecessor and the control transfer mechanism between
+/// the predecessor and this block is a fall-through.
+bool AsmPrinter::isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB)
+ const {
+ // If this is a landing pad, it isn't a fall through. If it has no preds,
+ // then nothing falls through to it.
+ if (MBB->isLandingPad() || MBB->pred_empty())
+ return false;
+
+ // If there isn't exactly one predecessor, it can't be a fall through.
+ MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), PI2 = PI;
+ ++PI2;
+ if (PI2 != MBB->pred_end())
+ return false;
+
+ // The predecessor has to be immediately before this block.
+ const MachineBasicBlock *Pred = *PI;
+
+ if (!Pred->isLayoutSuccessor(MBB))
+ return false;
+
+ // If the block is completely empty, then it definitely does fall through.
+ if (Pred->empty())
+ return true;
+
+ // Otherwise, check the last instruction.
+ const MachineInstr &LastInst = Pred->back();
+ return !LastInst.getDesc().isBarrier();
+}
+
+
+
GCMetadataPrinter *AsmPrinter::GetOrCreateGCPrinter(GCStrategy *S) {
if (!S->usesMetadata())
return 0;