[assembler] [cleanup] Cleanup RelocInfoWriter

Remove an unused constructor and an unused field, and compute a more
tight {kMaxSize}.
Beside being a cleanup, this might sometimes allow us to allocate a
little bit less memory on 32 bit systems.

R=mstarzinger@chromium.org

Change-Id: Ibf8fef231325f1b9047e2c7f4c66430797729fc1
Reviewed-on: https://chromium-review.googlesource.com/873534Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50696}

src/assembler.cc

@@ -449,7 +449,6 @@ void RelocInfoWriter::Write(const RelocInfo* rinfo) {
     }
   }
   last_pc_ = rinfo->pc();
-  last_mode_ = rmode;
 #ifdef DEBUG
   DCHECK_LE(begin_pos - pos_, kMaxSize);
 #endif

src/assembler.h

@@ -635,7 +635,6 @@ class RelocInfo {
 class RelocInfoWriter BASE_EMBEDDED {
  public:
   RelocInfoWriter() : pos_(nullptr), last_pc_(nullptr) {}
-  RelocInfoWriter(byte* pos, byte* pc) : pos_(pos), last_pc_(pc) {}
 
   byte* pos() const { return pos_; }
   byte* last_pc() const { return last_pc_; }
@@ -651,10 +650,7 @@ class RelocInfoWriter BASE_EMBEDDED {
 
   // Max size (bytes) of a written RelocInfo. Longest encoding is
   // ExtraTag, VariableLengthPCJump, ExtraTag, pc_delta, data_delta.
-  // On ia32 and arm this is 1 + 4 + 1 + 1 + 4 = 11.
-  // On x64 this is 1 + 4 + 1 + 1 + 8 == 15;
-  // Here we use the maximum of the two.
-  static const int kMaxSize = 15;
+  static constexpr int kMaxSize = 1 + 4 + 1 + 1 + kPointerSize;
 
  private:
   inline uint32_t WriteLongPCJump(uint32_t pc_delta);
@@ -669,7 +665,6 @@ class RelocInfoWriter BASE_EMBEDDED {
 
   byte* pos_;
   byte* last_pc_;
-  RelocInfo::Mode last_mode_;
 
   DISALLOW_COPY_AND_ASSIGN(RelocInfoWriter);
 };