Debug Info: Move the complex expression handling (=the remainder) of

emitDebugLocValue() into DwarfExpression.

Ought to be NFC, but it actually uncovered a bug in the debug-loc-asan.ll
testcase. The testcase checks that the address of variable "y" is stored
at [RSP+16], which also lines up with the comment.
It also check(ed) that the *value* of "y" is stored in RDI before that,
but that is actually incorrect, since RDI is the very value that is
stored in [RSP+16]. Here's the assembler output:

	movb	2147450880(%rcx), %r8b
	#DEBUG_VALUE: bar:y <- RDI
	cmpb	$0, %r8b
	movq	%rax, 32(%rsp)          # 8-byte Spill
	movq	%rsi, 24(%rsp)          # 8-byte Spill
	movq	%rdi, 16(%rsp)          # 8-byte Spill
.Ltmp3:
	#DEBUG_VALUE: bar:y <- [RSP+16]

Fixed the comment to spell out the correct register and the check to
expect an address rather than a value.

Note that the range that is emitted for the RDI location was and is still
wrong, it claims to begin at the function prologue, but really it should
start where RDI is first assigned.

llvm-svn: 225851

1 files changed, 12 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 870b9716039..f164f1c8513 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -15,6 +15,7 @@
 #define LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXPRESSION_H
 
 #include "llvm/Support/DataTypes.h"
+#include "llvm/IR/DebugInfo.h"
 
 namespace llvm {
 
@@ -81,8 +82,18 @@ public:
   void AddSignedConstant(int Value);
   /// Emit an unsigned constant.
   void AddUnsignedConstant(unsigned Value);
-};
 
+  /// Emit an entire DIExpression on top of a machine register location.
+  /// \param PieceOffsetInBits If this is one piece out of a fragmented
+  /// location, this is the offset of the piece inside the entire variable.
+  void AddMachineRegExpression(DIExpression Expr, unsigned MachineReg,
+                               unsigned PieceOffsetInBits = 0);
+  /// Emit a the operations in a DIExpression, starting from element I.
+  /// \param PieceOffsetInBits If this is one piece out of a fragmented
+  /// location, this is the offset of the piece inside the entire variable.
+  void AddExpression(DIExpression Expr, unsigned PieceOffsetInBits = 0,
+                     unsigned I = 0);
+};
 
 /// DwarfExpression implementation for .debug_loc entries.
 class DebugLocDwarfExpression : public DwarfExpression {