[DWARF parser] Fix broken address ranges construction.

Previous algorithm for constructing [Address ranges]->[Compile Units]
mapping was wrong. It somewhat relied on the assumption that address ranges
for different compile units may not overlap. It is not so.
For example, two compile units may contain the definition of the same
linkonce_odr function. These definitions will be merged at link-time,
resulting in equivalent .debug_ranges entries for both these units

Instead of sorting and merging original address ranges (from .debug_ranges
and .debug_aranges), implement a different approach: save endpoints
of all ranges, and then use a sweep-line approach to construct
the desired mapping. If we find that certain address maps to
several compilation units, we just pick any of them.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210860 91177308-0d34-0410-b5e6-96231b3b80d8

test/DebugInfo/llvm-symbolizer.test

@@ -18,6 +18,7 @@ RUN: echo "%p/Inputs/macho-universal:i386 0x1f67" >> %t.input
 RUN: echo "%p/Inputs/macho-universal:x86_64 0x100000f05" >> %t.input
 RUN: echo "%p/Inputs/llvm-symbolizer-dwo-test 0x400514" >> %t.input
 RUN: echo "%p/Inputs/fission-ranges.elf-x86_64 0x720" >> %t.input
+RUN: echo "%p/Inputs/arange-overlap.elf-x86_64 0x714" >> %t.input
 
 RUN: llvm-symbolizer --functions=linkage --inlining --demangle=false \
 RUN:    --default-arch=i386 < %t.input | FileCheck %s
@@ -94,6 +95,9 @@ CHECK-NEXT: llvm-symbolizer-dwo-test.cc:11
 CHECK: main
 CHECK-NEXT: {{.*}}fission-ranges.cc:6
 
+CHECK: _ZN1S3bazEv
+CHECK-NEXT: {{.*}}arange-overlap.cc:6
+
 RUN: echo "unexisting-file 0x1234" > %t.input2
 RUN: llvm-symbolizer < %t.input2