Debug Info: Simplify Frame Index handling in DBG_VALUE Machine Instructions

Rather than using the full power of target-specific addressing modes in
DBG_VALUEs with Frame Indicies, simply use Frame Index + Offset. This
reduces the complexity of debug info handling down to two
representations of values (reg+offset and frame index+offset) rather
than three or four.

Ideally we could ensure that frame indicies had been eliminated by the
time we reached an assembly or dwarf generation, but I haven't spent the
time to figure out where the FIs are leaking through into that & whether
there's a good place to convert them. Some FI+offset=>reg+offset
conversion is done (see PrologEpilogInserter, for example) which is
necessary for some SelectionDAG assumptions about registers, I believe,
but it might be possible to make this a more thorough conversion &
ensure there are no remaining FIs no matter how instruction selection
is performed.

llvm-svn: 184066

1 files changed, 4 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 475017abf84..5f689d20095 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -401,7 +401,8 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
   // Insert DBG_VALUE instructions for function arguments to the entry block.
   for (unsigned i = 0, e = FuncInfo->ArgDbgValues.size(); i != e; ++i) {
     MachineInstr *MI = FuncInfo->ArgDbgValues[e-i-1];
-    unsigned Reg = MI->getOperand(0).getReg();
+    bool hasFI = MI->getOperand(0).isFI();
+    unsigned Reg = hasFI ? TRI.getFrameRegister(*MF) : MI->getOperand(0).getReg();
     if (TargetRegisterInfo::isPhysicalRegister(Reg))
       EntryMBB->insert(EntryMBB->begin(), MI);
     else {
@@ -414,6 +415,8 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
     // If Reg is live-in then update debug info to track its copy in a vreg.
     DenseMap<unsigned, unsigned>::iterator LDI = LiveInMap.find(Reg);
     if (LDI != LiveInMap.end()) {
+      assert(!hasFI && "There's no handling of frame pointer updating here yet "
+                       "- add if needed");
       MachineInstr *Def = RegInfo->getVRegDef(LDI->second);
       MachineBasicBlock::iterator InsertPos = Def;
       const MDNode *Variable =