[dsymutil] Fix handling of inlined_subprogram low_pcs

The value of an inlined subprogram low_pc attribute should not
get relocated, but it can happen that it matches the enclosing
function's start address and thus gets the generic treatment.
Special case it to avoid applying the PC offset twice.

llvm-svn: 246406

test/tools/dsymutil/ARM/dummy-debug-map-amr64.map

@@ -0,0 +1,15 @@
+# This is a dummy debug map used for some tests where the contents of the
+# map are just an implementation detail. The tests wanting to use that file
+# should put all there object files in an explicitely named sub-directory
+# of Inputs, and they should be named 1.o, 2.o, ...
+# As not finding an object file or symbols isn't a fatal error for dsymutil,
+# you can extend this file with as much object files and symbols as needed.
+
+---
+triple:          'arm64-apple-darwin'
+objects:
+  - filename: 1.o
+    symbols:
+      - { sym: _bar, objAddr: 0x0, binAddr: 0x10000, size: 0x10 }
+...
+

test/tools/dsymutil/ARM/inlined-low_pc.c

@@ -0,0 +1,15 @@
+/* Compiled with: clang -arch=arm64 -O2 -g -c inlined_low_pc.c */
+
+static int foo(int i) { return 42 + i; }
+int bar(int a) { return foo(a); }
+
+// RUN: llvm-dsymutil -f -y %p/dummy-debug-map-amr64.map -oso-prepend-path %p/../Inputs/inlined-low_pc -o - | llvm-dwarfdump - | FileCheck %s
+
+// CHECK: DW_TAG_subprogram
+// CHECK: DW_AT_low_pc{{.*}}0x0000000000010000
+// CHECK: DW_AT_name{{.*}}"bar"
+// CHECK-NOT: NULL
+// CHECK: DW_TAG_inlined_subroutine
+// CHECK-NEXT: DW_AT_abstract_origin{{.*}}"foo"
+// CHECK-NEXT: DW_AT_low_pc{{.*}}0x0000000000010000
+

test/tools/dsymutil/ARM/lit.local.cfg

@@ -2,3 +2,6 @@ if not 'ARM' in config.root.targets:
     config.unsupported = True
 if not 'AArch64' in config.root.targets:
     config.unsupported = True
+
+config.suffixes = ['.test', '.cpp', '.c']
+

tools/dsymutil/DwarfLinker.cpp

@@ -1206,6 +1206,7 @@ private:
     const char *Name, *MangledName;         ///< Names.
     uint32_t NameOffset, MangledNameOffset; ///< Offsets in the string pool.
 
+    uint64_t OrigLowPc;  ///< Value of AT_low_pc in the input DIE
     uint64_t OrigHighPc; ///< Value of AT_high_pc in the input DIE
     int64_t PCOffset;    ///< Offset to apply to PC addresses inside a function.
 
@@ -1214,8 +1215,8 @@ private:
 
     AttributesInfo()
         : Name(nullptr), MangledName(nullptr), NameOffset(0),
-          MangledNameOffset(0), OrigHighPc(0), PCOffset(0), HasLowPc(false),
-          IsDeclaration(false) {}
+          MangledNameOffset(0), OrigLowPc(UINT64_MAX), OrigHighPc(0),
+          PCOffset(0), HasLowPc(false), IsDeclaration(false) {}
   };
 
   /// \brief Helper for cloneDIE.
@@ -2274,7 +2275,12 @@ unsigned DwarfLinker::cloneAddressAttribute(DIE &Die, AttributeSpec AttrSpec,
   if (AttrSpec.Attr == dwarf::DW_AT_low_pc) {
     if (Die.getTag() == dwarf::DW_TAG_inlined_subroutine ||
         Die.getTag() == dwarf::DW_TAG_lexical_block)
-      Addr += Info.PCOffset;
+      // The low_pc of a block or inline subroutine might get
+      // relocated because it happens to match the low_pc of the
+      // enclosing subprogram. To prevent issues with that, always use
+      // the low_pc from the input DIE if relocations have been applied.
+      Addr = (Info.OrigLowPc != UINT64_MAX ? Info.OrigLowPc : Addr) +
+             Info.PCOffset;
     else if (Die.getTag() == dwarf::DW_TAG_compile_unit) {
       Addr = Unit.getLowPc();
       if (Addr == UINT64_MAX)
@@ -2522,6 +2528,11 @@ DIE *DwarfLinker::cloneDIE(const DWARFDebugInfoEntryMinimal &InputDIE,
     // high_pc value is done in cloneAddressAttribute().
     AttrInfo.OrigHighPc =
         InputDIE.getAttributeValueAsAddress(&U, dwarf::DW_AT_high_pc, 0);
+    // Also store the low_pc. It might get relocated in an
+    // inline_subprogram that happens at the beginning of its
+    // inlining function.
+    AttrInfo.OrigLowPc =
+        InputDIE.getAttributeValueAsAddress(&U, dwarf::DW_AT_low_pc, UINT64_MAX);
   }
 
   // Reset the Offset to 0 as we will be working on the local copy of