From 83aa6d02d82007f57af92a4caeec6bf72aeb1fc0 Mon Sep 17 00:00:00 2001
From: Shankar Easwaran <shankare@codeaurora.org>
Date: Wed, 1 Apr 2015 03:07:01 +0000
Subject: [PATCH] [ELF][Hexagon] Add comments related to hexagon relocations.

No functional changes.

llvm-svn: 233783
---
 .../ReaderWriter/ELF/Hexagon/HexagonEncodings.h   |  1 +
 .../ELF/Hexagon/HexagonRelocationFunctions.h      | 15 +++++++++------
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/lld/lib/ReaderWriter/ELF/Hexagon/HexagonEncodings.h b/lld/lib/ReaderWriter/ELF/Hexagon/HexagonEncodings.h
index 3e12786704a2..d7831533aee2 100644
--- a/lld/lib/ReaderWriter/ELF/Hexagon/HexagonEncodings.h
+++ b/lld/lib/ReaderWriter/ELF/Hexagon/HexagonEncodings.h
@@ -7,6 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 Instruction insn_encodings[] = {
+  // InsnMask   CompareMask BitMask IsDuplexInstruction
   { 0xffe00004, 0x40000000, 0x20f8, 0x0 },
   { 0xffe03080, 0x9ca03080, 0xf60, 0x0 },
   { 0xf9e00000, 0x48c00000, 0x61f20ff, 0x0 },
diff --git a/lld/lib/ReaderWriter/ELF/Hexagon/HexagonRelocationFunctions.h b/lld/lib/ReaderWriter/ELF/Hexagon/HexagonRelocationFunctions.h
index 6bc6db28d9e2..8e57fec67c74 100644
--- a/lld/lib/ReaderWriter/ELF/Hexagon/HexagonRelocationFunctions.h
+++ b/lld/lib/ReaderWriter/ELF/Hexagon/HexagonRelocationFunctions.h
@@ -16,12 +16,15 @@
 namespace lld {
 namespace elf {
 
-/// \brief HexagonInstruction which is used to store various values
+/// \brief Applying fixup on Hexagon requires the relocator to fetch the fixup
+/// mask from the instruction. To fetch the fixup encoding, the linker uses a
+/// static array that contains the instruction mask, the compare mask and the
+/// relocation mask.
 typedef struct {
-  uint32_t insnMask;
-  uint32_t insnCmpMask;
-  uint32_t insnBitMask;
-  bool isDuplex;
+  uint32_t insnMask;    // Instruction mask.
+  uint32_t insnCmpMask; // Compare mask.
+  uint32_t insnBitMask; // Relocation mask.
+  bool isDuplex;        // Indicates if the instruction is a duplex instruction.
 } Instruction;
 
 #include "HexagonEncodings.h"
@@ -37,7 +40,7 @@ inline uint32_t findv4bitmask(uint8_t *location) {
     if (((insn_encodings[i].insnMask) & insn) == insn_encodings[i].insnCmpMask)
       return insn_encodings[i].insnBitMask;
   }
-  llvm_unreachable("found unknown instruction");
+  llvm_unreachable("found unknown Hexagon instruction");
 }
 
 } // elf