DWARF: Unify form size handling code

Summary:
This patch replaces the two switches which are deducing the size of
various forms with a single implementation. I have put the new
implementation into BinaryFormat, to avoid introducing dependencies
between the two independent libraries (DebugInfo and CodeGen) that need
this functionality.

Reviewers: aprantl, JDevlieghere, dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D44418

llvm-svn: 327486

1 files changed, 87 insertions, 0 deletions

diff --git a/llvm/lib/BinaryFormat/Dwarf.cpp b/llvm/lib/BinaryFormat/Dwarf.cpp
index e345b3acabd..1a809a178fe 100644
--- a/llvm/lib/BinaryFormat/Dwarf.cpp
+++ b/llvm/lib/BinaryFormat/Dwarf.cpp
@@ -580,6 +580,93 @@ StringRef llvm::dwarf::IndexString(unsigned Idx) {
   }
 }
 
+Optional<uint8_t> llvm::dwarf::getFixedFormByteSize(dwarf::Form Form,
+                                                    FormParams Params) {
+  switch (Form) {
+  case DW_FORM_addr:
+    if (Params)
+      return Params.AddrSize;
+    return None;
+
+  case DW_FORM_block:          // ULEB128 length L followed by L bytes.
+  case DW_FORM_block1:         // 1 byte length L followed by L bytes.
+  case DW_FORM_block2:         // 2 byte length L followed by L bytes.
+  case DW_FORM_block4:         // 4 byte length L followed by L bytes.
+  case DW_FORM_string:         // C-string with null terminator.
+  case DW_FORM_sdata:          // SLEB128.
+  case DW_FORM_udata:          // ULEB128.
+  case DW_FORM_ref_udata:      // ULEB128.
+  case DW_FORM_indirect:       // ULEB128.
+  case DW_FORM_exprloc:        // ULEB128 length L followed by L bytes.
+  case DW_FORM_strx:           // ULEB128.
+  case DW_FORM_addrx:          // ULEB128.
+  case DW_FORM_loclistx:       // ULEB128.
+  case DW_FORM_rnglistx:       // ULEB128.
+  case DW_FORM_GNU_addr_index: // ULEB128.
+  case DW_FORM_GNU_str_index:  // ULEB128.
+    return None;
+
+  case DW_FORM_ref_addr:
+    if (Params)
+      return Params.getRefAddrByteSize();
+    return None;
+
+  case DW_FORM_flag:
+  case DW_FORM_data1:
+  case DW_FORM_ref1:
+  case DW_FORM_strx1:
+  case DW_FORM_addrx1:
+    return 1;
+
+  case DW_FORM_data2:
+  case DW_FORM_ref2:
+  case DW_FORM_strx2:
+  case DW_FORM_addrx2:
+    return 2;
+
+  case DW_FORM_strx3:
+    return 3;
+
+  case DW_FORM_data4:
+  case DW_FORM_ref4:
+  case DW_FORM_ref_sup4:
+  case DW_FORM_strx4:
+  case DW_FORM_addrx4:
+    return 4;
+
+  case DW_FORM_strp:
+  case DW_FORM_GNU_ref_alt:
+  case DW_FORM_GNU_strp_alt:
+  case DW_FORM_line_strp:
+  case DW_FORM_sec_offset:
+  case DW_FORM_strp_sup:
+    if (Params)
+      return Params.getDwarfOffsetByteSize();
+    return None;
+
+  case DW_FORM_data8:
+  case DW_FORM_ref8:
+  case DW_FORM_ref_sig8:
+  case DW_FORM_ref_sup8:
+    return 8;
+
+  case DW_FORM_flag_present:
+    return 0;
+
+  case DW_FORM_data16:
+    return 16;
+
+  case DW_FORM_implicit_const:
+    // The implicit value is stored in the abbreviation as a SLEB128, and
+    // there no data in debug info.
+    return 0;
+
+  default:
+    break;
+  }
+  return None;
+}
+
 bool llvm::dwarf::isValidFormForVersion(Form F, unsigned Version,
                                         bool ExtensionsOk) {
   if (FormVendor(F) == DWARF_VENDOR_DWARF) {