[llvm] 8e1d532 - [Object] Simplify RELR decoding

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2021-10-16T15:03:14-07:00
New Revision: 8e1d532707fdf590da6dee53f33cca8a79d133e5

URL: https://github.com/llvm/llvm-project/commit/8e1d532707fdf590da6dee53f33cca8a79d133e5
DIFF: https://github.com/llvm/llvm-project/commit/8e1d532707fdf590da6dee53f33cca8a79d133e5.diff

LOG: [Object] Simplify RELR decoding

Added: 
    

Modified: 
    llvm/lib/Object/ELF.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Object/ELF.cpp b/llvm/lib/Object/ELF.cpp
index cd9f8813e74c3..1eabc29ac5d45 100644
--- a/llvm/lib/Object/ELF.cpp
+++ b/llvm/lib/Object/ELF.cpp
@@ -336,40 +336,26 @@ ELFFile<ELFT>::decode_relrs(Elf_Relr_Range relrs) const {
   std::vector<Elf_Rel> Relocs;
 
   // Word type: uint32_t for Elf32, and uint64_t for Elf64.
-  typedef typename ELFT::uint Word;
+  using Addr = typename ELFT::uint;
 
-  // Word size in number of bytes.
-  const size_t WordSize = sizeof(Word);
-
-  // Number of bits used for the relocation offsets bitmap.
-  // These many relative relocations can be encoded in a single entry.
-  const size_t NBits = 8*WordSize - 1;
-
-  Word Base = 0;
-  for (const Elf_Relr &R : relrs) {
-    Word Entry = R;
-    if ((Entry&1) == 0) {
+  Addr Base = 0;
+  for (Elf_Relr R : relrs) {
+    typename ELFT::uint Entry = R;
+    if ((Entry & 1) == 0) {
       // Even entry: encodes the offset for next relocation.
       Rel.r_offset = Entry;
       Relocs.push_back(Rel);
       // Set base offset for subsequent bitmap entries.
-      Base = Entry + WordSize;
-      continue;
-    }
-
-    // Odd entry: encodes bitmap for relocations starting at base.
-    Word Offset = Base;
-    while (Entry != 0) {
-      Entry >>= 1;
-      if ((Entry&1) != 0) {
-        Rel.r_offset = Offset;
-        Relocs.push_back(Rel);
-      }
-      Offset += WordSize;
+      Base = Entry + sizeof(Addr);
+    } else {
+      // Odd entry: encodes bitmap for relocations starting at base.
+      for (Addr Offset = Base; (Entry >>= 1) != 0; Offset += sizeof(Addr))
+        if ((Entry & 1) != 0) {
+          Rel.r_offset = Offset;
+          Relocs.push_back(Rel);
+        }
+      Base += (CHAR_BIT * sizeof(Entry) - 1) * sizeof(Addr);
     }
-
-    // Advance base offset by NBits words.
-    Base += NBits * WordSize;
   }
 
   return Relocs;