Allow ARM if-converter to be run after post allocation scheduling.
- This fixed a number of bugs in if-converter, tail merging, and post-allocation
scheduler. If-converter now runs branch folding / tail merging first to
maximize if-conversion opportunities.
- Also changed the t2IT instruction slightly. It now defines the ITSTATE
register which is read by instructions in the IT block.
- Added Thumb2 specific hazard recognizer to ensure the scheduler doesn't
change the instruction ordering in the IT block (since IT mask has been
finalized). It also ensures no other instructions can be scheduled between
instructions in the IT block.
This is not yet enabled.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106344 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index 6eb3fab..8d3ad80 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -1306,6 +1306,34 @@
return MI0->isIdenticalTo(MI1, MachineInstr::IgnoreVRegDefs);
}
+bool ARMBaseInstrInfo::isSchedulingBoundary(const MachineInstr *MI,
+ const MachineBasicBlock *MBB,
+ const MachineFunction &MF) const {
+ // Terminators and labels can't be scheduled around.
+ if (MI->getDesc().isTerminator() || MI->isLabel())
+ return true;
+
+ // Treat the start of the IT block as a scheduling boundary, but schedule
+ // t2IT along with all instructions following it.
+ // FIXME: This is a big hammer. But the alternative is to add all potential
+ // true and anti dependencies to IT block instructions as implicit operands
+ // to the t2IT instruction. The added compile time and complexity does not
+ // seem worth it.
+ MachineBasicBlock::const_iterator I = MI;
+ if (++I != MBB->end() && I->getOpcode() == ARM::t2IT)
+ return true;
+
+ // Don't attempt to schedule around any instruction that defines
+ // a stack-oriented pointer, as it's unlikely to be profitable. This
+ // saves compile time, because it doesn't require every single
+ // stack slot reference to depend on the instruction that does the
+ // modification.
+ if (MI->definesRegister(ARM::SP))
+ return true;
+
+ return false;
+}
+
/// getInstrPredicate - If instruction is predicated, returns its predicate
/// condition, otherwise returns AL. It also returns the condition code
/// register by reference.