IT instructions are considered to be scheduling hazards, but are scheduled

with the following instructions. This is done via trickery by considering the
instruction preceding the IT to be the hazard. Care must be taken to ensure
it's the first non-debug instruction, or the presence of debug info will
affect codegen.

Part of the continuing work for rdar://7797940, making ARM code-gen unaffected
by the presence of debug information.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106871 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 1 deletions

diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index b9bc0b8..7ef7fd6 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -1410,6 +1410,15 @@ bool ARMBaseInstrInfo::shouldScheduleLoadsNear(SDNode *Load1, SDNode *Load2,
 bool ARMBaseInstrInfo::isSchedulingBoundary(const MachineInstr *MI,
                                             const MachineBasicBlock *MBB,
                                             const MachineFunction &MF) const {
+  // Debug info is never a scheduling boundary. It's necessary to be explicit
+  // due to the special treatment of IT instructions below, otherwise a
+  // dbg_value followed by an IT will result in the IT instruction being
+  // considered a scheduling hazard, which is wrong. It should be the actual
+  // instruction preceding the dbg_value instruction(s), just like it is
+  // when debug info is not present.
+  if (MI->isDebugValue())
+    return false;
+
   // Terminators and labels can't be scheduled around.
   if (MI->getDesc().isTerminator() || MI->isLabel())
     return true;
@@ -1421,7 +1430,10 @@ bool ARMBaseInstrInfo::isSchedulingBoundary(const MachineInstr *MI,
   // 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)
+  // Make sure to skip any dbg_value instructions
+  while (++I != MBB->end() && I->isDebugValue())
+    ;
+  if (I != MBB->end() && I->getOpcode() == ARM::t2IT)
     return true;
 
   // Don't attempt to schedule around any instruction that defines