[codeview] Emit S_FRAMEPROC and use S_DEFRANGE_FRAMEPOINTER_REL

Summary:
Before this change, LLVM would always describe locals on the stack as
being relative to some specific register, RSP, ESP, EBP, ESI, etc.
Variables in stack memory are pretty common, so there is a special
S_DEFRANGE_FRAMEPOINTER_REL symbol for them. This change uses it to
reduce the size of our debug info.

On top of the size savings, there are cases on 32-bit x86 where local
variables are addressed from ESP, but ESP changes across the function.
Unlike in DWARF, there is no FPO data to describe the stack adjustments
made to push arguments onto the stack and pop them off after the call,
which makes it hard for the debugger to find the local variables in
frames further up the stack.

To handle this, CodeView has a special VFRAME register, which
corresponds to the $T0 variable set by our FPO data in 32-bit.  Offsets
to local variables are instead relative to this value.

This is part of PR38857.

Reviewers: hans, zturner, javed.absar

Subscribers: aprantl, hiraditya, JDevlieghere, llvm-commits

Differential Revision: https://reviews.llvm.org/D52217

llvm-svn: 343543

1 files changed, 28 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
index 6d7b97c5dd6..3836862f0a8 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
@@ -54,6 +54,9 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
   BumpPtrAllocator Allocator;
   codeview::GlobalTypeTableBuilder TypeTable;
 
+  /// The codeview CPU type used by the translation unit.
+  codeview::CPUType TheCPU;
+
   /// Represents the most general definition range.
   struct LocalVarDefRange {
     /// Indicates that variable data is stored in memory relative to the
@@ -140,6 +143,28 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
     const MCSymbol *End = nullptr;
     unsigned FuncId = 0;
     unsigned LastFileId = 0;
+
+    /// Number of bytes allocated in the prologue for all local stack objects.
+    unsigned FrameSize = 0;
+
+    /// Number of bytes of parameters on the stack.
+    unsigned ParamSize = 0;
+
+    /// Number of bytes pushed to save CSRs.
+    unsigned CSRSize = 0;
+
+    /// Two-bit value indicating which register is the designated frame pointer
+    /// register for local variables. Included in S_FRAMEPROC.
+    codeview::EncodedFramePtrReg EncodedLocalFramePtrReg =
+        codeview::EncodedFramePtrReg::None;
+
+    /// Two-bit value indicating which register is the designated frame pointer
+    /// register for stack parameters. Included in S_FRAMEPROC.
+    codeview::EncodedFramePtrReg EncodedParamFramePtrReg =
+        codeview::EncodedFramePtrReg::None;
+
+    codeview::FrameProcedureOptions FrameProcOpts;
+
     bool HaveLineInfo = false;
   };
   FunctionInfo *CurFn = nullptr;
@@ -293,10 +318,11 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
   void recordLocalVariable(LocalVariable &&Var, const LexicalScope *LS);
 
   /// Emits local variables in the appropriate order.
-  void emitLocalVariableList(ArrayRef<LocalVariable> Locals);
+  void emitLocalVariableList(const FunctionInfo &FI,
+                             ArrayRef<LocalVariable> Locals);
 
   /// Emits an S_LOCAL record and its associated defined ranges.
-  void emitLocalVariable(const LocalVariable &Var);
+  void emitLocalVariable(const FunctionInfo &FI, const LocalVariable &Var);
 
   /// Emits a sequence of lexical block scopes and their children.
   void emitLexicalBlockList(ArrayRef<LexicalBlock *> Blocks,