[DebugInfo] DW_OP_deref_size in PrologEpilogInserter.

The PrologEpilogInserter need to insert a DW_OP_deref_size before
prepending a memory location expression to an already implicit
expression to avoid having the existing expression act on the memory
address instead of the value behind it.

The reason for using DW_OP_deref_size and not plain DW_OP_deref is that
big-endian targets need to read the right size as simply truncating a
larger read would yield the wrong result (LSB bytes are not at the lower
address).

This re-commit fixes issues reported in the first one. Namely deref was
inserted under wrong conditions and additionally the deref_size argument
was incorrectly encoded.

Differential Revision: https://reviews.llvm.org/D59687

llvm-svn: 359535

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 18bedf0b902..145504946a5 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -139,6 +139,8 @@ protected:
   /// Emit a raw unsigned value.
   virtual void emitUnsigned(uint64_t Value) = 0;
 
+  virtual void emitData1(uint8_t Value) = 0;
+
   virtual void emitBaseTypeRef(uint64_t Idx) = 0;
 
   /// Emit a normalized unsigned constant.
@@ -264,6 +266,7 @@ class DebugLocDwarfExpression final : public DwarfExpression {
   void emitOp(uint8_t Op, const char *Comment = nullptr) override;
   void emitSigned(int64_t Value) override;
   void emitUnsigned(uint64_t Value) override;
+  void emitData1(uint8_t Value) override;
   void emitBaseTypeRef(uint64_t Idx) override;
   bool isFrameRegister(const TargetRegisterInfo &TRI,
                        unsigned MachineReg) override;
@@ -281,6 +284,7 @@ const AsmPrinter ≈
   void emitOp(uint8_t Op, const char *Comment = nullptr) override;
   void emitSigned(int64_t Value) override;
   void emitUnsigned(uint64_t Value) override;
+  void emitData1(uint8_t Value) override;
   void emitBaseTypeRef(uint64_t Idx) override;
   bool isFrameRegister(const TargetRegisterInfo &TRI,
                        unsigned MachineReg) override;