From 2142fff539f2198cd61dc28c41e506c87fe6e162 Mon Sep 17 00:00:00 2001
From: Jonah Williams <jonahwilliams@google.com>
Date: Sat, 10 Jun 2023 10:14:29 -0700
Subject: [PATCH] [Impeller] Fix vulkan gradient nan issue.
 (flutter/engine#42715)

Fixes https://github.com/flutter/flutter/issues/128603

We were hitting a nan issue. GLSL has different relaxed precision semantics than vulkan does, and didn't hit it for some reason.
---
 .../shaders/linear_gradient_ssbo_fill.frag     | 14 ++++++--------
 engine/src/flutter/impeller/tools/malioc.json  | 18 +++++++++---------
 2 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/engine/src/flutter/impeller/entity/shaders/linear_gradient_ssbo_fill.frag b/engine/src/flutter/impeller/entity/shaders/linear_gradient_ssbo_fill.frag
index 183b3b7978..1b2990d9eb 100644
--- a/engine/src/flutter/impeller/entity/shaders/linear_gradient_ssbo_fill.frag
+++ b/engine/src/flutter/impeller/entity/shaders/linear_gradient_ssbo_fill.frag
@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include <impeller/gradient.glsl>
 #include <impeller/texture.glsl>
 #include <impeller/types.glsl>
 
@@ -30,9 +29,9 @@ highp in vec2 v_position;
 out vec4 frag_color;
 
 void main() {
-  vec2 start_to_end = frag_info.end_point - frag_info.start_point;
-  vec2 start_to_position = v_position - frag_info.start_point;
-  float t =
+  highp vec2 start_to_end = frag_info.end_point - frag_info.start_point;
+  highp vec2 start_to_position = v_position - frag_info.start_point;
+  highp float t =
       dot(start_to_position, start_to_end) / dot(start_to_end, start_to_end);
 
   if ((t < 0.0 || t > 1.0) && frag_info.tile_mode == kTileModeDecal) {
@@ -41,21 +40,20 @@ void main() {
   }
   t = IPFloatTile(t, frag_info.tile_mode);
 
-  vec4 result_color = vec4(0);
   for (int i = 1; i < frag_info.colors_length; i++) {
     ColorPoint prev_point = color_data.colors[i - 1];
     ColorPoint current_point = color_data.colors[i];
     if (t >= prev_point.stop && t <= current_point.stop) {
       float delta = (current_point.stop - prev_point.stop);
       if (delta < 0.001) {
-        result_color = current_point.color;
+        frag_color = current_point.color;
       } else {
         float ratio = (t - prev_point.stop) / delta;
-        result_color = mix(prev_point.color, current_point.color, ratio);
+        frag_color = mix(prev_point.color, current_point.color, ratio);
       }
       break;
     }
   }
   frag_color =
-      vec4(result_color.xyz * result_color.a, result_color.a) * frag_info.alpha;
+      vec4(frag_color.xyz * frag_color.a, frag_color.a) * frag_info.alpha;
 }
diff --git a/engine/src/flutter/impeller/tools/malioc.json b/engine/src/flutter/impeller/tools/malioc.json
index aef3c8891d..27784bffa5 100644
--- a/engine/src/flutter/impeller/tools/malioc.json
+++ b/engine/src/flutter/impeller/tools/malioc.json
@@ -11338,7 +11338,7 @@
       "uses_late_zs_update": false,
       "variants": {
         "Main": {
-          "fp16_arithmetic": 70,
+          "fp16_arithmetic": 32,
           "has_stack_spilling": false,
           "performance": {
             "longest_path_bound_pipelines": [
@@ -11366,10 +11366,10 @@
               "varying"
             ],
             "shortest_path_cycles": [
-              0.109375,
+              0.125,
               0.09375,
-              0.109375,
-              0.0,
+              0.125,
+              0.0625,
               0.0,
               0.25,
               0.0
@@ -11378,10 +11378,10 @@
               "load_store"
             ],
             "total_cycles": [
-              0.59375,
-              0.359375,
-              0.59375,
-              0.0625,
+              0.65625,
+              0.375,
+              0.65625,
+              0.125,
               4.0,
               0.25,
               0.0
@@ -11389,7 +11389,7 @@
           },
           "stack_spill_bytes": 0,
           "thread_occupancy": 100,
-          "uniform_registers_used": 12,
+          "uniform_registers_used": 14,
           "work_registers_used": 15
         }
       }