[WebAssembly] Fix the CFG Stackifier to handle unoptimized branches
If a branch both branches to and falls through to the same block, treat it as
an explicit branch.
llvm-svn: 255803
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
index 6412442..6ac5366 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
@@ -251,6 +251,19 @@
#endif
}
+/// Test whether Pred has any terminators explicitly branching to MBB, as
+/// opposed to falling through. Note that it's possible (eg. in unoptimized
+/// code) for a branch instruction to both branch to a block and fallthrough
+/// to it, so we check the actual branch operands to see if there are any
+/// explicit mentions.
+static bool ExplicitlyBranchesTo(MachineBasicBlock *Pred, MachineBasicBlock *MBB) {
+ for (MachineInstr &MI : Pred->terminators())
+ for (MachineOperand &MO : MI.explicit_operands())
+ if (MO.isMBB() && MO.getMBB() == MBB)
+ return true;
+ return false;
+}
+
/// Insert a BLOCK marker for branches to MBB (if needed).
static void PlaceBlockMarker(MachineBasicBlock &MBB, MachineFunction &MF,
SmallVectorImpl<MachineBasicBlock *> &ScopeTops,
@@ -266,8 +279,7 @@
for (MachineBasicBlock *Pred : MBB.predecessors())
if (Pred->getNumber() < MBBNumber) {
Header = Header ? MDT.findNearestCommonDominator(Header, Pred) : Pred;
- if (!Pred->isLayoutSuccessor(&MBB) ||
- !(Pred->empty() || !Pred->back().isBarrier()))
+ if (ExplicitlyBranchesTo(Pred, &MBB))
IsBranchedTo = true;
}
if (!Header)