Cleanup and document MachineLocation.

Clarify documentation and API to make the difference between register and
register-indirect addressed locations more explicit. Put in a comment
to point out that with the current implementation we cannot specify
a register-indirect location with offset 0 (a breg 0 in DWARF).
No functionality change intended.

rdar://problem/13658587

llvm-svn: 180641

2 files changed, 9 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 9187c6c2bec..864787d32fd 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -813,7 +813,7 @@ void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc) const {
   // caller might be in the middle of an dwarf expression. We should
   // probably assert that Reg >= 0 once debug info generation is more mature.
 
-  if (int Offset =  MLoc.getOffset()) {
+  if (MLoc.isIndirect()) {
     if (Reg < 32) {
       OutStreamer.AddComment(
         dwarf::OperationEncodingString(dwarf::DW_OP_breg0 + Reg));
@@ -824,7 +824,7 @@ void AsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc) const {
       OutStreamer.AddComment(Twine(Reg));
       EmitULEB128(Reg);
     }
-    EmitSLEB128(Offset);
+    EmitSLEB128(MLoc.getOffset());
   } else {
     if (Reg < 32) {
       OutStreamer.AddComment(
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 270a10ad37a..c4e77aafabc 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1131,7 +1131,13 @@ static DotDebugLocEntry getDebugLocEntry(AsmPrinter *Asm,
   }
   if (MI->getOperand(0).isReg() && MI->getOperand(1).isImm()) {
     MachineLocation MLoc;
-    MLoc.set(MI->getOperand(0).getReg(), MI->getOperand(1).getImm());
+    // TODO: Currently an offset of 0 in a DBG_VALUE means
+    // we need to generate a direct register value.
+    // There is no way to specify an indirect value with offset 0.
+    if (MI->getOperand(1).getImm() == 0)
+      MLoc.set(MI->getOperand(0).getReg());
+    else
+      MLoc.set(MI->getOperand(0).getReg(), MI->getOperand(1).getImm());
     return DotDebugLocEntry(FLabel, SLabel, MLoc, Var);
   }
   if (MI->getOperand(0).isImm())