[lldb/DWARF] Remove "range lower than function low_pc" check (#132395)

The check is not correct for discontinuous functions, as one of the
blocks could very well begin before the function entry point. To catch
dead-stripped ranges, I check whether the functions is after the first
known code address. I don't print any error in this case as that is a
common/expected situation.

This avoids many errors like:
```
error: ld-linux-x86-64.so.2 0x00085f3b: adding range [0x0000000000001ae8-0x0000000000001b07) which has a 
base that is less than the function's low PC 0x000000000001cfb0. Please file a bug and attach the file at
 the start of this error message
```
when debugging binaries on debian trixie because the dynamic linker
(ld-linux) contains discontinuous functions.

If the block ranges is not a subrange of the enclosing block then this
will range will currently be added to the outer block as well (i.e., we
get the same behavior that's currently possible for non-subrange blocks
larger than function_low_pc). However, this code path is buggy and I'd
like to change that (#117725).

Author: labath

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

@@ -1323,7 +1323,7 @@ bool SymbolFileDWARF::ParseDebugMacros(CompileUnit &comp_unit) {
 
 size_t SymbolFileDWARF::ParseBlocksRecursive(CompileUnit &comp_unit,
                                              Block *parent_block, DWARFDIE die,
-                                             addr_t subprogram_low_pc) {
+                                             addr_t function_file_addr) {
   size_t blocks_added = 0;
   for (; die; die = die.GetSibling()) {
     dw_tag_t tag = die.Tag();
@@ -1346,19 +1346,9 @@ size_t SymbolFileDWARF::ParseBlocksRecursive(CompileUnit &comp_unit,
                                  decl_line, decl_column, call_file, call_line,
                                  call_column, nullptr)) {
       for (const llvm::DWARFAddressRange &range : ranges) {
-        if (!range.valid())
-          continue;
-        if (range.LowPC >= subprogram_low_pc)
-          block->AddRange(Block::Range(range.LowPC - subprogram_low_pc,
+        if (range.valid() && range.LowPC >= m_first_code_address)
+          block->AddRange(Block::Range(range.LowPC - function_file_addr,
                                        range.HighPC - range.LowPC));
-        else {
-          GetObjectFile()->GetModule()->ReportError(
-              "{0:x8}: adding range [{1:x16}-{2:x16}) which has a base "
-              "that is less than the function's low PC {3:x16}. Please file "
-              "a bug and attach the file at the "
-              "start of this error message",
-              block->GetID(), range.LowPC, range.HighPC, subprogram_low_pc);
-        }
       }
       block->FinalizeRanges();
 
@@ -1386,7 +1376,7 @@ size_t SymbolFileDWARF::ParseBlocksRecursive(CompileUnit &comp_unit,
 
       if (die.HasChildren()) {
         blocks_added += ParseBlocksRecursive(
-            comp_unit, block, die.GetFirstChild(), subprogram_low_pc);
+            comp_unit, block, die.GetFirstChild(), function_file_addr);
       }
     }
   }

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h

@@ -391,7 +391,7 @@ class SymbolFileDWARF : public SymbolFileCommon {
   Function *ParseFunction(CompileUnit &comp_unit, const DWARFDIE &die);
 
   size_t ParseBlocksRecursive(CompileUnit &comp_unit, Block *parent_block,
-                              DWARFDIE die, lldb::addr_t subprogram_low_pc);
+                              DWARFDIE die, lldb::addr_t function_file_addr);
 
   size_t ParseTypes(const SymbolContext &sc, const DWARFDIE &die,
                     bool parse_siblings, bool parse_children);