[mips] Deal with empty blocks in the mips hazard scheduler
This patch teaches the hazard scheduler how to handle empty blocks
when search for the next real instruction when dealing with forbidden
slots.
Reviewers: slthakur
Differential Revision: https://reviews.llvm.org/D31293
llvm-svn: 299427
diff --git a/llvm/lib/Target/Mips/MipsHazardSchedule.cpp b/llvm/lib/Target/Mips/MipsHazardSchedule.cpp
index 87446e3..f6fcf6e 100644
--- a/llvm/lib/Target/Mips/MipsHazardSchedule.cpp
+++ b/llvm/lib/Target/Mips/MipsHazardSchedule.cpp
@@ -103,23 +103,24 @@
// Find the next real instruction from the current position, looking through
// basic block boundaries.
-static Iter getNextMachineInstr(Iter Position, MachineBasicBlock *Parent) {
+static std::pair<Iter, bool> getNextMachineInstr(Iter Position, MachineBasicBlock * Parent) {
if (Position == Parent->end()) {
- MachineBasicBlock *Succ = Parent->getNextNode();
- if (Succ != nullptr && Parent->isSuccessor(Succ)) {
- Position = Succ->begin();
- Parent = Succ;
- } else {
- llvm_unreachable(
- "Should have identified the end of the function earlier!");
- }
+ do {
+ MachineBasicBlock *Succ = Parent->getNextNode();
+ if (Succ != nullptr && Parent->isSuccessor(Succ)) {
+ Position = Succ->begin();
+ Parent = Succ;
+ } else {
+ return std::make_pair(Position, true);
+ }
+ } while (Parent->empty());
}
Iter Instr = getNextMachineInstrInBB(Position);
if (Instr == Parent->end()) {
return getNextMachineInstr(Instr, Parent);
}
- return Instr;
+ return std::make_pair(Instr, false);
}
bool MipsHazardSchedule::runOnMachineFunction(MachineFunction &MF) {
@@ -145,7 +146,9 @@
bool LastInstInFunction =
std::next(I) == FI->end() && std::next(FI) == MF.end();
if (!LastInstInFunction) {
- Inst = getNextMachineInstr(std::next(I), &*FI);
+ std::pair<Iter, bool> Res = getNextMachineInstr(std::next(I), &*FI);
+ LastInstInFunction |= Res.second;
+ Inst = Res.first;
}
if (LastInstInFunction || !TII->SafeInForbiddenSlot(*Inst)) {