Insert dbg_value instructions for function entry block liveins (i.e. function arguments).

llvm-svn: 102368

1 files changed, 30 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineRegisterInfo.cpp b/llvm/lib/CodeGen/MachineRegisterInfo.cpp
index 850ade25da5..724d81cdba8 100644
--- a/llvm/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/llvm/lib/CodeGen/MachineRegisterInfo.cpp
@@ -12,8 +12,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/Support/CommandLine.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Support/CommandLine.h"
 using namespace llvm;
 
 MachineRegisterInfo::MachineRegisterInfo(const TargetRegisterInfo &TRI) {
@@ -219,6 +220,30 @@ static void EmitLiveInCopy(MachineBasicBlock *MBB,
   }
 }
 
+/// InsertLiveInDbgValue - Insert a DBG_VALUE instruction for each live-in
+/// register that has a corresponding source information metadata. e.g.
+/// function parameters.
+static void InsertLiveInDbgValue(MachineBasicBlock *MBB,
+                                 MachineBasicBlock::iterator InsertPos,
+                                 unsigned LiveInReg, unsigned VirtReg,
+                                 const MachineRegisterInfo &MRI,
+                                 const TargetInstrInfo &TII) {
+  for (MachineRegisterInfo::use_iterator UI = MRI.use_begin(VirtReg),
+         UE = MRI.use_end(); UI != UE; ++UI) {
+    MachineInstr *UseMI = &*UI;
+    if (!UseMI->isDebugValue() || UseMI->getParent() != MBB)
+      continue;
+    // Found local dbg_value. FIXME: Verify it's not possible to have multiple
+    // dbg_value's which reference the vr in the same mbb.
+    uint64_t Offset = UseMI->getOperand(1).getImm();
+    const MDNode *MDPtr = UseMI->getOperand(2).getMetadata();    
+    BuildMI(*MBB, InsertPos, InsertPos->getDebugLoc(),
+            TII.get(TargetOpcode::DBG_VALUE))
+      .addReg(LiveInReg).addImm(Offset).addMetadata(MDPtr);
+    return;
+  }
+}
+
 /// EmitLiveInCopies - Emit copies to initialize livein virtual registers
 /// into the given entry block.
 void
@@ -235,6 +260,8 @@ MachineRegisterInfo::EmitLiveInCopies(MachineBasicBlock *EntryMBB,
         const TargetRegisterClass *RC = getRegClass(LI->second);
         EmitLiveInCopy(EntryMBB, InsertPos, LI->second, LI->first,
                        RC, CopyRegMap, *this, TRI, TII);
+        InsertLiveInDbgValue(EntryMBB, InsertPos,
+                             LI->first, LI->second, *this, TII);
       }
   } else {
     // Emit the copies into the top of the block.
@@ -246,6 +273,8 @@ MachineRegisterInfo::EmitLiveInCopies(MachineBasicBlock *EntryMBB,
                                         LI->second, LI->first, RC, RC);
         assert(Emitted && "Unable to issue a live-in copy instruction!\n");
         (void) Emitted;
+        InsertLiveInDbgValue(EntryMBB, EntryMBB->begin(),
+                             LI->first, LI->second, *this, TII);
       }
   }