MachineBasicBlock: add liveout iterator aware of which liveins are defined by the runtime.

Using this in RegAlloc fast reduces register pressure, and in some cases allows
x86 code to compile that wouldn't before.

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index d792ad490487..1011f52476d2 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -21,6 +21,7 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/SlotIndexes.h"
 #include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/CodeGen/TargetLowering.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/Config/llvm-config.h"
@@ -1629,6 +1630,23 @@ MachineBasicBlock::livein_iterator MachineBasicBlock::livein_begin() const {
   return LiveIns.begin();
 }
 
+MachineBasicBlock::liveout_iterator MachineBasicBlock::liveout_begin() const {
+  const MachineFunction &MF = *getParent();
+  assert(MF.getProperties().hasProperty(
+      MachineFunctionProperties::Property::TracksLiveness) &&
+      "Liveness information is accurate");
+
+  const TargetLowering &TLI = *MF.getSubtarget().getTargetLowering();
+  MCPhysReg ExceptionPointer = 0, ExceptionSelector = 0;
+  if (MF.getFunction().hasPersonalityFn()) {
+    auto PersonalityFn = MF.getFunction().getPersonalityFn();
+    ExceptionPointer = TLI.getExceptionPointerRegister(PersonalityFn);
+    ExceptionSelector = TLI.getExceptionSelectorRegister(PersonalityFn);
+  }
+
+  return liveout_iterator(*this, ExceptionPointer, ExceptionSelector, false);
+}
+
 const MBBSectionID MBBSectionID::ColdSectionID(MBBSectionID::SectionType::Cold);
 const MBBSectionID
     MBBSectionID::ExceptionSectionID(MBBSectionID::SectionType::Exception);