From 9fff11133d1890a2733e8a61ba976492fe800c99 Mon Sep 17 00:00:00 2001
From: Mike Klein <mtklein@chromium.org>
Date: Wed, 24 May 2017 11:37:52 -0400
Subject: [PATCH] better extend: alloc once, no recursion

Change-Id: I6a8cee08248462e4e17196028758dd8d44093b28
Reviewed-on: https://skia-review.googlesource.com/17831
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
---
 src/core/SkRasterPipeline.cpp | 26 +++++++++++++++++++-------
 src/core/SkRasterPipeline.h   |  2 +-
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/src/core/SkRasterPipeline.cpp b/src/core/SkRasterPipeline.cpp
index 0f4c1f4..dc25e5a 100644
--- a/src/core/SkRasterPipeline.cpp
+++ b/src/core/SkRasterPipeline.cpp
@@ -12,6 +12,7 @@ SkRasterPipeline::SkRasterPipeline(SkArenaAlloc* alloc) : fAlloc(alloc) {
 }
 void SkRasterPipeline::reset() {
     fStages      = nullptr;
+    fNumStages   = 0;
     fSlotsNeeded = 1;  // We always need one extra slot for just_return().
 }
 
@@ -21,22 +22,33 @@ void SkRasterPipeline::append(StockStage stage, void* ctx) {
 }
 void SkRasterPipeline::unchecked_append(StockStage stage, void* ctx) {
     fStages = fAlloc->make<StageList>( StageList{fStages, stage, ctx} );
+    fNumStages   += 1;
     fSlotsNeeded += ctx ? 2 : 1;
 }
 
 void SkRasterPipeline::extend(const SkRasterPipeline& src) {
-    this->extend(src.fStages);
-}
-void SkRasterPipeline::extend(const StageList* stages) {
-    if (!stages) {
+    if (src.empty()) {
         return;
     }
-    this->extend(stages->prev);
-    this->unchecked_append(stages->stage, stages->ctx);
+    auto stages = fAlloc->makeArrayDefault<StageList>(src.fNumStages);
+
+    int n = src.fNumStages;
+    const StageList* st = src.fStages;
+    while (n --> 1) {
+        stages[n]      = *st;
+        stages[n].prev = &stages[n-1];
+        st = st->prev;
+    }
+    stages[0]      = *st;
+    stages[0].prev = fStages;
+
+    fStages = &stages[src.fNumStages - 1];
+    fNumStages   += src.fNumStages;
+    fSlotsNeeded += src.fSlotsNeeded - 1;  // Don't double count just_returns().
 }
 
 void SkRasterPipeline::dump() const {
-    SkDebugf("SkRasterPipeline, (in reverse)\n");
+    SkDebugf("SkRasterPipeline, %d stages (in reverse)\n", fNumStages);
     for (auto st = fStages; st; st = st->prev) {
         const char* name = "";
         switch (st->stage) {
diff --git a/src/core/SkRasterPipeline.h b/src/core/SkRasterPipeline.h
index 117ecf3..da38102 100644
--- a/src/core/SkRasterPipeline.h
+++ b/src/core/SkRasterPipeline.h
@@ -156,10 +156,10 @@ private:
 
     static void BuildPipeline(const StageList*, const SkJumper_Engine&, void**);
     void unchecked_append(StockStage, void*);
-    void extend(const StageList*);
 
     SkArenaAlloc* fAlloc;
     StageList*    fStages;
+    int           fNumStages;
     int           fSlotsNeeded;
 };
 
-- 
2.7.4