[lldb/DWARF] Remove "range lower than function low_pc" check

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.

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

@@ -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)
+        if (range.valid() && range.LowPC >= m_first_code_address)
           block->AddRange(Block::Range(range.LowPC - subprogram_low_pc,
                                        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();
 

lldb/test/Shell/SymbolFile/DWARF/range-lower-then-low-pc.s

@@ -6,28 +6,13 @@
 # RUN: %lldb %t -o "image lookup -v -n look_me_up" -o exit | FileCheck %s
 
 # CHECK:      1 match found in {{.*}}
-# CHECK:      Summary: {{.*}}`foo + 6 [inlined] foo_inl + 1
-# CHECK-NEXT:          {{.*}}`foo + 5
-# CHECK:      Blocks: id = {{.*}}, ranges = [0x00000000-0x00000003)[0x00000004-0x00000008)
-# CHECK-NEXT:         id = {{.*}}, ranges = [0x00000001-0x00000002)[0x00000005-0x00000007), name = "foo_inl"
+# CHECK:      Summary: {{.*}}`foo - 3 [inlined] foo_inl + 1
+# CHECK-NEXT:          {{.*}}`foo - 4
+# CHECK:      Blocks: id = {{.*}}, ranges = [0x00000000-0x00000004)[0x00000005-0x00000008)
+# CHECK-NEXT:         id = {{.*}}, ranges = [0x00000001-0x00000003)[0x00000006-0x00000007), name = "foo_inl"
 
         .text
 
-        .type   foo,@function
-foo:
-        nop
-.Lfoo_inl:
-        nop
-.Lfoo_inl_end:
-        nop
-.Lfoo_end:
-        .size   foo, .Lfoo_end-foo
-
-bar:
-        nop
-.Lbar_end:
-        .size   bar, .Lbar_end-bar
-
         .section        .text.__part1,"ax",@progbits
 foo.__part.1:
         nop
@@ -42,6 +27,21 @@ look_me_up:
         .size   foo.__part.1, .Lfoo.__part.1_end-foo.__part.1
 
 
+bar:
+        nop
+.Lbar_end:
+        .size   bar, .Lbar_end-bar
+
+        .type   foo,@function
+foo:
+        nop
+.Lfoo_inl:
+        nop
+.Lfoo_inl_end:
+        nop
+.Lfoo_end:
+        .size   foo, .Lfoo_end-foo
+
         .section        .debug_abbrev,"",@progbits
         .byte   1                               # Abbreviation Code
         .byte   17                              # DW_TAG_compile_unit