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

3 files changed, 29 insertions, 44 deletions

diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 9b39264928..842381b42a 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -42,6 +42,7 @@
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Timer.h"
 #include "llvm/Target/Mangler.h"
+#include "llvm/Target/TargetFrameLowering.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetLowering.h"
 #include "llvm/Target/TargetLoweringObjectFile.h"
@@ -591,8 +592,17 @@ static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
   } else if (MI->getOperand(0).isCImm()) {
     MI->getOperand(0).getCImm()->getValue().print(OS, false /*isSigned*/);
   } else {
-    assert(MI->getOperand(0).isReg() && "Unknown operand type");
-    unsigned Reg = MI->getOperand(0).getReg();
+    unsigned Reg;
+    if (MI->getOperand(0).isReg()) {
+      Reg = MI->getOperand(0).getReg();
+      Deref = Offset != 0; // FIXME: use a better sentinel value so that deref
+                           // of a reg with a zero offset is valid
+    } else {
+      assert(MI->getOperand(0).isFI() && "Unknown operand type");
+      const TargetFrameLowering *TFI = AP.TM.getFrameLowering();
+      Offset += TFI->getFrameIndexReference(*AP.MF, MI->getOperand(0).getIndex(), Reg);
+      Deref = true;
+    }
     if (Reg == 0) {
       // Suppress offset, it is not meaningful here.
       OS << "undef";
@@ -600,8 +610,6 @@ static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
       AP.OutStreamer.EmitRawText(OS.str());
       return true;
     }
-    Deref = Offset != 0; // FIXME: use a better sentinel value so that deref of
-                         // a reg with a zero offset is valid
     if (Deref)
       OS << '[';
     OS << AP.TM.getRegisterInfo()->getName(Reg);
diff --git a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index c3b6c10605..9e8f9aaa9a 100644
--- a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -1525,43 +1525,23 @@ DIE *CompileUnit::constructVariableDIE(DbgVariable *DV, bool isScopeAbstract) {
   // Check if variable is described by a DBG_VALUE instruction.
   if (const MachineInstr *DVInsn = DV->getMInsn()) {
     bool updated = false;
-    if (DVInsn->getNumOperands() == 3) {
-      if (DVInsn->getOperand(0).isReg()) {
-        const MachineOperand RegOp = DVInsn->getOperand(0);
-        const TargetRegisterInfo *TRI = Asm->TM.getRegisterInfo();
-        if (DVInsn->getOperand(1).isImm() &&
-            TRI->getFrameRegister(*Asm->MF) == RegOp.getReg()) {
-          unsigned FrameReg = 0;
-          const TargetFrameLowering *TFI = Asm->TM.getFrameLowering();
-          int Offset =
-            TFI->getFrameIndexReference(*Asm->MF,
-                                        DVInsn->getOperand(1).getImm(),
-                                        FrameReg);
-          MachineLocation Location(FrameReg, Offset);
-          addVariableAddress(DV, VariableDie, Location);
-
-        } else if (RegOp.getReg())
-          addVariableAddress(DV, VariableDie,
-                                         MachineLocation(RegOp.getReg()));
-        updated = true;
-      }
-      else if (DVInsn->getOperand(0).isImm())
-        updated =
-          addConstantValue(VariableDie, DVInsn->getOperand(0),
-                                       DV->getType());
-      else if (DVInsn->getOperand(0).isFPImm())
-        updated =
-          addConstantFPValue(VariableDie, DVInsn->getOperand(0));
-      else if (DVInsn->getOperand(0).isCImm())
-        updated =
-          addConstantValue(VariableDie,
-                                       DVInsn->getOperand(0).getCImm(),
-                                       DV->getType().isUnsignedDIType());
-    } else {
-      addVariableAddress(DV, VariableDie,
-                                     Asm->getDebugValueLocation(DVInsn));
+    assert(DVInsn->getNumOperands() == 3);
+    if (DVInsn->getOperand(0).isReg()) {
+      const MachineOperand RegOp = DVInsn->getOperand(0);
+      if (int64_t Offset = DVInsn->getOperand(1).getImm()) {
+        MachineLocation Location(RegOp.getReg(), Offset);
+        addVariableAddress(DV, VariableDie, Location);
+      } else if (RegOp.getReg())
+        addVariableAddress(DV, VariableDie, MachineLocation(RegOp.getReg()));
       updated = true;
-    }
+    } else if (DVInsn->getOperand(0).isImm())
+      updated =
+          addConstantValue(VariableDie, DVInsn->getOperand(0), DV->getType());
+    else if (DVInsn->getOperand(0).isFPImm())
+      updated = addConstantFPValue(VariableDie, DVInsn->getOperand(0));
+    else if (DVInsn->getOperand(0).isCImm())
+      updated = addConstantValue(VariableDie, DVInsn->getOperand(0).getCImm(),
+                                 DV->getType().isUnsignedDIType());
     if (!updated) {
       // If variableDie is not updated then DBG_VALUE instruction does not
       // have valid variable info.
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 7915e2f50a..23eb569c6f 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1170,10 +1170,7 @@ static DotDebugLocEntry getDebugLocEntry(AsmPrinter *Asm,
                                          const MachineInstr *MI) {
   const MDNode *Var =  MI->getOperand(MI->getNumOperands() - 1).getMetadata();
 
-  if (MI->getNumOperands() != 3) {
-    MachineLocation MLoc = Asm->getDebugValueLocation(MI);
-    return DotDebugLocEntry(FLabel, SLabel, MLoc, Var);
-  }
+  assert(MI->getNumOperands() == 3);
   if (MI->getOperand(0).isReg() && MI->getOperand(1).isImm()) {
     MachineLocation MLoc;
     // TODO: Currently an offset of 0 in a DBG_VALUE means