Make a function to correctly extract the DW_AT_high_pc given the low pc value.

DWARF 4 and later supports encoding the PC as an address or as as offset from the low PC. Clients using DWARFDie should be insulated from how to extract the high PC value. This function takes care of extracting the form value and looking for the correct form.

Differential Revision: https://reviews.llvm.org/D27885

llvm-svn: 290131

1 files changed, 22 insertions, 13 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index 981f33c1f4f..94777109e44 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -245,21 +245,30 @@ DWARFDie::getRangesBaseAttribute() const {
   return getAttributeValueAsSectionOffset(DW_AT_GNU_ranges_base);
 }
 
-bool DWARFDie::getLowAndHighPC(uint64_t &LowPC, uint64_t &HighPC) const {
-  if (auto LowPCVal = getAttributeValueAsAddress(DW_AT_low_pc))
-    LowPC = *LowPCVal;
-  else
-    return false;
+Optional<uint64_t> DWARFDie::getHighPC(uint64_t LowPC) const {
+  if (auto FormValue = getAttributeValue(DW_AT_high_pc)) {
+    if (auto Address = FormValue->getAsAddress()) {
+      // High PC is an address.
+      return Address;
+    }
+    if (auto Offset = FormValue->getAsUnsignedConstant()) {
+      // High PC is an offset from LowPC.
+      return LowPC + *Offset;
+    }
+  }
+  return None;
+}
 
-  if (auto HighPCVal = getAttributeValueAsAddress(DW_AT_high_pc)) {
-    // High PC is an address.
-    HighPC = *HighPCVal;
-  } else if (auto Offset = getAttributeValueAsUnsignedConstant(DW_AT_high_pc)) {
-    // High PC is an offset from LowPC.
-    HighPC = LowPC + *Offset;
-  } else
+bool DWARFDie::getLowAndHighPC(uint64_t &LowPC, uint64_t &HighPC) const {
+  auto LowPcAddr = getAttributeValueAsAddress(DW_AT_low_pc);
+  if (!LowPcAddr)
     return false;
-  return true;
+  if (auto HighPcAddr = getHighPC(*LowPcAddr)) {
+    LowPC = *LowPcAddr;
+    HighPC = *HighPcAddr;
+    return true;
+  }
+  return false;
 }
 
 DWARFAddressRangesVector