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[PATCH] [mips] Fix forbidden slot hazard handling

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MipsHazardSchedule has to determine what the next physical machine instruction
is to decide whether to insert a nop. In case where a branch with a forbidden
slot appears at the end of a basic block, first *real* instruction of the next
physical basic block was determined using getFirstNonDebugInstr().

Unfortunately this only considers DBG_VALUEs and not other transient opcodes
such as EHLABEL. As EHLABEL passes the SafeInForbiddenSlot predicate and the
instruction after the EHLABEL can be a CTI, we observed test failures in the
LNT testsuite.

Reviewers: dsanders

Differential Review: http://reviews.llvm.org/D19051

llvm-svn: 268052
This commit is contained in:
Simon Dardis 2016-04-29 16:04:18 +00:00
parent d4659dc8ea
commit cbfb26b5e3
1 changed files with 11 additions and 3 deletions
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14
lib/Target/Mips/MipsHazardSchedule.cpp
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@ -91,6 +91,14 @@ FunctionPass *llvm::createMipsHazardSchedule() {
return new MipsHazardSchedule();
}
// Find the next real instruction from the current position.
static Iter getNextMachineInstr(Iter Position) {
Iter I = Position, E = Position->getParent()->end();
I = std::find_if_not(I, E, [](const Iter &Insn) { return Insn->isTransient(); });
assert(I != E);
return I;
}
bool MipsHazardSchedule::runOnMachineFunction(MachineFunction &MF) {
const MipsSubtarget *STI =
@ -113,14 +121,14 @@ bool MipsHazardSchedule::runOnMachineFunction(MachineFunction &MF) {
bool InsertNop = false;
// Next instruction in the basic block.
if (std::next(I) != FI->end() &&
!TII->SafeInForbiddenSlot(*std::next(I))) {
!TII->SafeInForbiddenSlot(*getNextMachineInstr(std::next(I)))) {
InsertNop = true;
} else {
// Next instruction in the physical successor basic block.
for (auto *Succ : FI->successors()) {
if (FI->isLayoutSuccessor(Succ) &&
Succ->getFirstNonDebugInstr() != Succ->end() &&
!TII->SafeInForbiddenSlot(*Succ->getFirstNonDebugInstr())) {
getNextMachineInstr(Succ->begin()) != Succ->end() &&
!TII->SafeInForbiddenSlot(*getNextMachineInstr(Succ->begin()))) {
InsertNop = true;
break;
}