A fix for PR21176.
DW_OP_const <const> doesn't describe a constant value, but a value at a constant address.
The proper way to describe a constant value is DW_OP_constu <const>, DW_OP_stack_value.
Added DW_OP_stack_value to the stack.
Marked incorrect-variable-debugloc1.ll to xfail for PowerPC64, while the the failure (PR21881)
is being investigated.
llvm-svn: 224098
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 230ea46..b7e9d65 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1722,6 +1722,18 @@
Streamer.EmitInt8(dwarf::DW_OP_constu, "DW_OP_constu");
Streamer.EmitULEB128(Value.getInt());
}
+ // The proper way to describe a constant value is
+ // DW_OP_constu <const>, DW_OP_stack_value.
+ // Unfortunately, DW_OP_stack_value was not available until DWARF-4,
+ // so we will continue to generate DW_OP_constu <const> for DWARF-2
+ // and DWARF-3. Technically, this is incorrect since DW_OP_const <const>
+ // actually describes a value at a constant addess, not a constant value.
+ // However, in the past there was no better way to describe a constant
+ // value, so the producers and consumers started to rely on heuristics
+ // to disambiguate the value vs. location status of the expression.
+ // See PR21176 for more details.
+ if (getDwarfVersion() >= 4)
+ Streamer.EmitInt8(dwarf::DW_OP_stack_value, "DW_OP_stack_value");
} else if (Value.isLocation()) {
MachineLocation Loc = Value.getLoc();
DIExpression Expr = Value.getExpression();