Reland "[DebugInfo] Support DWARF expressions in eh_frame"

Summary:
Original change was D43313 (r326932) and reverted by r326953 because it
broke an LLD test and a windows build. The LLD test was already fixed in
lld commit r326944 (thanks maskray). This is the original change with
the windows build fixed.

llvm-svn: 326970

1 files changed, 69 insertions, 0 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDataExtractor.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDataExtractor.cpp
index 861dd313fb0..03e31746139 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDataExtractor.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDataExtractor.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/DWARF/DWARFDataExtractor.h"
+#include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
 
 using namespace llvm;
@@ -25,3 +26,71 @@ uint64_t DWARFDataExtractor::getRelocatedValue(uint32_t Size, uint32_t *Off,
     *SecNdx = Rel->SectionIndex;
   return getUnsigned(Off, Size) + Rel->Value;
 }
+
+Optional<uint64_t>
+DWARFDataExtractor::getEncodedPointer(uint32_t *Offset, uint8_t Encoding,
+                                      uint64_t PCRelOffset) const {
+  if (Encoding == dwarf::DW_EH_PE_omit)
+    return None;
+
+  uint64_t Result = 0;
+  uint32_t OldOffset = *Offset;
+  // First get value
+  switch (Encoding & 0x0F) {
+  case dwarf::DW_EH_PE_absptr:
+    switch (getAddressSize()) {
+    case 2:
+    case 4:
+    case 8:
+      Result = getUnsigned(Offset, getAddressSize());
+      break;
+    default:
+      return None;
+    }
+    break;
+  case dwarf::DW_EH_PE_uleb128:
+    Result = getULEB128(Offset);
+    break;
+  case dwarf::DW_EH_PE_sleb128:
+    Result = getSLEB128(Offset);
+    break;
+  case dwarf::DW_EH_PE_udata2:
+    Result = getUnsigned(Offset, 2);
+    break;
+  case dwarf::DW_EH_PE_udata4:
+    Result = getUnsigned(Offset, 4);
+    break;
+  case dwarf::DW_EH_PE_udata8:
+    Result = getUnsigned(Offset, 8);
+    break;
+  case dwarf::DW_EH_PE_sdata2:
+    Result = getSigned(Offset, 2);
+    break;
+  case dwarf::DW_EH_PE_sdata4:
+    Result = getSigned(Offset, 4);
+    break;
+  case dwarf::DW_EH_PE_sdata8:
+    Result = getSigned(Offset, 8);
+    break;
+  default:
+    return None;
+  }
+  // Then add relative offset, if required
+  switch (Encoding & 0x70) {
+  case dwarf::DW_EH_PE_absptr:
+    // do nothing
+    break;
+  case dwarf::DW_EH_PE_pcrel:
+    Result += PCRelOffset;
+    break;
+  case dwarf::DW_EH_PE_datarel:
+  case dwarf::DW_EH_PE_textrel:
+  case dwarf::DW_EH_PE_funcrel:
+  case dwarf::DW_EH_PE_aligned:
+  default:
+    *Offset = OldOffset;
+    return None;
+  }
+
+  return Result;
+}