Split findUnwindSectionsByPhdr into target-specific functions.

Summary:
This further cleans up the control flow and makes it easier to
optimize and replace portions in a subsequent patch.

This should be NFC, but given the amount of #ifdeffing here,
it may not be. So will watch the buildbots closely.

Also, as this is purely moving existing code around, I plan to
ignore the lint errors.

Reviewers: compnerd, miyuki, mstorsjo

Subscribers: libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D75705

Author: Sterling-Augustine

libunwind/src/AddressSpace.hpp

@@ -409,24 +409,6 @@ LocalAddressSpace::getEncodedP(pint_t &addr, pint_t end, uint8_t encoding,
 // that don't help at all.
 #elif defined(_LIBUNWIND_ARM_EHABI) || defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
 
-struct _LIBUNWIND_HIDDEN dl_iterate_cb_data {
-  LocalAddressSpace *addressSpace;
-  UnwindInfoSections *sects;
-  uintptr_t targetAddr;
-};
-
-int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
-  auto cbdata = static_cast<dl_iterate_cb_data *>(data);
-  bool found_obj = false;
-  bool found_hdr = false;
-
-  assert(cbdata);
-  assert(cbdata->sects);
-
-  if (cbdata->targetAddr < pinfo->dlpi_addr) {
-    return false;
-  }
-
 #if !defined(Elf_Half)
   typedef ElfW(Half) Elf_Half;
 #endif
@@ -437,8 +419,8 @@ int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
   typedef ElfW(Addr) Elf_Addr;
 #endif
 
+static Elf_Addr calculateImageBase(struct dl_phdr_info *pinfo) {
   Elf_Addr image_base = pinfo->dlpi_addr;
-
 #if defined(__ANDROID__) && __ANDROID_API__ < 18
   if (image_base == 0) {
     // Normally, an image base of 0 indicates a non-PIE executable. On
@@ -456,11 +438,32 @@ int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
     }
   }
 #endif
+  return image_base;
+}
 
- #if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
+struct _LIBUNWIND_HIDDEN dl_iterate_cb_data {
+  LocalAddressSpace *addressSpace;
+  UnwindInfoSections *sects;
+  uintptr_t targetAddr;
+};
+
+#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
   #if !defined(_LIBUNWIND_SUPPORT_DWARF_INDEX)
-   #error "_LIBUNWIND_SUPPORT_DWARF_UNWIND requires _LIBUNWIND_SUPPORT_DWARF_INDEX on this platform."
+    #error "_LIBUNWIND_SUPPORT_DWARF_UNWIND requires _LIBUNWIND_SUPPORT_DWARF_INDEX on this platform."
   #endif
+
+int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
+  auto *cbdata = static_cast<dl_iterate_cb_data *>(data);
+  bool found_obj = false;
+  bool found_hdr = false;
+
+  assert(cbdata);
+  assert(cbdata->sects);
+
+  if (cbdata->targetAddr < pinfo->dlpi_addr)
+    return 0;
+
+  Elf_Addr image_base = calculateImageBase(pinfo);
   size_t object_length;
 
   for (Elf_Half i = 0; i < pinfo->dlpi_phnum; i++) {
@@ -492,7 +495,25 @@ int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
   } else {
     return false;
   }
- #else // defined(_LIBUNWIND_ARM_EHABI)
+}
+
+#else  // defined(LIBUNWIND_SUPPORT_DWARF_UNWIND)
+// Given all the #ifdef's above, the code here is for
+// defined(LIBUNWIND_ARM_EHABI)
+
+int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
+  auto *cbdata = static_cast<dl_iterate_cb_data *>(data);
+  bool found_obj = false;
+  bool found_hdr = false;
+
+  assert(cbdata);
+  assert(cbdata->sects);
+
+  if (cbdata->targetAddr < pinfo->dlpi_addr)
+    return 0;
+
+  Elf_Addr image_base = calculateImageBase(pinfo);
+
   for (Elf_Half i = 0; i < pinfo->dlpi_phnum; i++) {
     const Elf_Phdr *phdr = &pinfo->dlpi_phdr[i];
     if (phdr->p_type == PT_LOAD) {
@@ -508,8 +529,8 @@ int findUnwindSectionsByPhdr(struct dl_phdr_info *pinfo, size_t, void *data) {
     }
   }
   return found_obj && found_hdr;
- #endif
 }
+#endif  // defined(LIBUNWIND_SUPPORT_DWARF_UNWIND)
 #endif  // defined(_LIBUNWIND_ARM_EHABI) || defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)