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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184066 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 9 deletions

diff --git a/lib/CodeGen/InlineSpiller.cpp b/lib/CodeGen/InlineSpiller.cpp
index 3bdc30d..dd00d77 100644
--- a/lib/CodeGen/InlineSpiller.cpp
+++ b/lib/CodeGen/InlineSpiller.cpp
@@ -24,6 +24,7 @@
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineInstrBundle.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
@@ -1123,15 +1124,10 @@ void InlineSpiller::spillAroundUses(unsigned Reg) {
       uint64_t Offset = MI->getOperand(1).getImm();
       const MDNode *MDPtr = MI->getOperand(2).getMetadata();
       DebugLoc DL = MI->getDebugLoc();
-      if (MachineInstr *NewDV = TII.emitFrameIndexDebugValue(MF, StackSlot,
-                                                           Offset, MDPtr, DL)) {
-        DEBUG(dbgs() << "Modifying debug info due to spill:" << "\t" << *MI);
-        MachineBasicBlock *MBB = MI->getParent();
-        MBB->insert(MBB->erase(MI), NewDV);
-      } else {
-        DEBUG(dbgs() << "Removing debug info due to spill:" << "\t" << *MI);
-        MI->eraseFromParent();
-      }
+      DEBUG(dbgs() << "Modifying debug info due to spill:" << "\t" << *MI);
+      MachineBasicBlock *MBB = MI->getParent();
+      BuildMI(*MBB, MBB->erase(MI), DL, TII.get(TargetOpcode::DBG_VALUE))
+          .addFrameIndex(StackSlot).addImm(Offset).addMetadata(MDPtr);
       continue;
     }