JS VMs struggle to recognize when the condition part of a for loop is…

… constant, especially w.r.t. GLctx.getProgramParameter(), so make sure that no repeated computation is done in such paths. (#20439)
emscripten-core · Aug 29, 2024 · aec91e5 · aec91e5
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commit aec91e5
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Showing 9 changed files with 57 additions and 44 deletions.
diff --git a/src/library_webgl.js b/src/library_webgl.js
@@ -2182,7 +2182,8 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
       // maps integer locations back to uniform name strings, so that we can lazily fetch uniform array locations
       program.uniformArrayNamesById = {};
 
-      for (i = 0; i < GLctx.getProgramParameter(program, 0x8B86/*GL_ACTIVE_UNIFORMS*/); ++i) {
+      var numActiveUniforms = GLctx.getProgramParameter(program, 0x8B86/*GL_ACTIVE_UNIFORMS*/);
+      for (i = 0; i < numActiveUniforms; ++i) {
         var u = GLctx.getActiveUniform(program, i);
         var nm = u.name;
         var sz = u.size;
@@ -2499,8 +2500,9 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
 #if GL_POOL_TEMP_BUFFERS
     if (count <= {{{ GL_POOL_TEMP_BUFFERS_SIZE / 2 }}}) {
       // avoid allocation when uploading few enough uniforms
-      var view = miniTempWebGLIntBuffers[2*count];
-      for (var i = 0; i < 2*count; i += 2) {
+      count *= 2;
+      var view = miniTempWebGLIntBuffers[count];
+      for (var i = 0; i < count; i += 2) {
         view[i] = {{{ makeGetValue('value', '4*i', 'i32') }}};
         view[i+1] = {{{ makeGetValue('value', '4*i+4', 'i32') }}};
       }
@@ -2541,8 +2543,9 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
 #if GL_POOL_TEMP_BUFFERS
     if (count <= {{{ GL_POOL_TEMP_BUFFERS_SIZE / 3 }}}) {
       // avoid allocation when uploading few enough uniforms
-      var view = miniTempWebGLIntBuffers[3*count];
-      for (var i = 0; i < 3*count; i += 3) {
+      count *= 3;
+      var view = miniTempWebGLIntBuffers[count];
+      for (var i = 0; i < count; i += 3) {
         view[i] = {{{ makeGetValue('value', '4*i', 'i32') }}};
         view[i+1] = {{{ makeGetValue('value', '4*i+4', 'i32') }}};
         view[i+2] = {{{ makeGetValue('value', '4*i+8', 'i32') }}};
@@ -2584,8 +2587,9 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
 #if GL_POOL_TEMP_BUFFERS
     if (count <= {{{ GL_POOL_TEMP_BUFFERS_SIZE / 4 }}}) {
       // avoid allocation when uploading few enough uniforms
-      var view = miniTempWebGLIntBuffers[4*count];
-      for (var i = 0; i < 4*count; i += 4) {
+      count *= 4;
+      var view = miniTempWebGLIntBuffers[count];
+      for (var i = 0; i < count; i += 4) {
         view[i] = {{{ makeGetValue('value', '4*i', 'i32') }}};
         view[i+1] = {{{ makeGetValue('value', '4*i+4', 'i32') }}};
         view[i+2] = {{{ makeGetValue('value', '4*i+8', 'i32') }}};
@@ -2669,8 +2673,9 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
 #if GL_POOL_TEMP_BUFFERS
     if (count <= {{{ GL_POOL_TEMP_BUFFERS_SIZE / 2 }}}) {
       // avoid allocation when uploading few enough uniforms
-      var view = miniTempWebGLFloatBuffers[2*count];
-      for (var i = 0; i < 2*count; i += 2) {
+      count *= 2;
+      var view = miniTempWebGLFloatBuffers[count];
+      for (var i = 0; i < count; i += 2) {
         view[i] = {{{ makeGetValue('value', '4*i', 'float') }}};
         view[i+1] = {{{ makeGetValue('value', '4*i+4', 'float') }}};
       }
@@ -2711,8 +2716,9 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
 #if GL_POOL_TEMP_BUFFERS
     if (count <= {{{ GL_POOL_TEMP_BUFFERS_SIZE / 3 }}}) {
       // avoid allocation when uploading few enough uniforms
-      var view = miniTempWebGLFloatBuffers[3*count];
-      for (var i = 0; i < 3*count; i += 3) {
+      count *= 3;
+      var view = miniTempWebGLFloatBuffers[count];
+      for (var i = 0; i < count; i += 3) {
         view[i] = {{{ makeGetValue('value', '4*i', 'float') }}};
         view[i+1] = {{{ makeGetValue('value', '4*i+4', 'float') }}};
         view[i+2] = {{{ makeGetValue('value', '4*i+8', 'float') }}};
@@ -2758,7 +2764,8 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
       // hoist the heap out of the loop for size and for pthreads+growth.
       var heap = HEAPF32;
       value = {{{ getHeapOffset('value', 'float') }}};
-      for (var i = 0; i < 4 * count; i += 4) {
+      count *= 4;
+      for (var i = 0; i < count; i += 4) {
         var dst = value + i;
         view[i] = heap[dst];
         view[i + 1] = heap[dst + 1];
@@ -2802,8 +2809,9 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
 #if GL_POOL_TEMP_BUFFERS
     if (count <= {{{ GL_POOL_TEMP_BUFFERS_SIZE / 4 }}}) {
       // avoid allocation when uploading few enough uniforms
-      var view = miniTempWebGLFloatBuffers[4*count];
-      for (var i = 0; i < 4*count; i += 4) {
+      count *= 4;
+      var view = miniTempWebGLFloatBuffers[count];
+      for (var i = 0; i < count; i += 4) {
         view[i] = {{{ makeGetValue('value', '4*i', 'float') }}};
         view[i+1] = {{{ makeGetValue('value', '4*i+4', 'float') }}};
         view[i+2] = {{{ makeGetValue('value', '4*i+8', 'float') }}};
@@ -2846,8 +2854,9 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
 #if GL_POOL_TEMP_BUFFERS
     if (count <= {{{ GL_POOL_TEMP_BUFFERS_SIZE / 9 }}}) {
       // avoid allocation when uploading few enough uniforms
-      var view = miniTempWebGLFloatBuffers[9*count];
-      for (var i = 0; i < 9*count; i += 9) {
+      count *= 9;
+      var view = miniTempWebGLFloatBuffers[count];
+      for (var i = 0; i < count; i += 9) {
         view[i] = {{{ makeGetValue('value', '4*i', 'float') }}};
         view[i+1] = {{{ makeGetValue('value', '4*i+4', 'float') }}};
         view[i+2] = {{{ makeGetValue('value', '4*i+8', 'float') }}};
@@ -2899,7 +2908,8 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
       // hoist the heap out of the loop for size and for pthreads+growth.
       var heap = HEAPF32;
       value = {{{ getHeapOffset('value', 'float') }}};
-      for (var i = 0; i < 16 * count; i += 16) {
+      count *= 16;
+      for (var i = 0; i < count; i += 16) {
         var dst = value + i;
         view[i] = heap[dst];
         view[i + 1] = heap[dst + 1];
@@ -3351,21 +3361,24 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
       {{{ makeSetValue('p', '0', 'log.length + 1', 'i32') }}};
     } else if (pname == 0x8B87 /* GL_ACTIVE_UNIFORM_MAX_LENGTH */) {
       if (!program.maxUniformLength) {
-        for (var i = 0; i < GLctx.getProgramParameter(program, 0x8B86/*GL_ACTIVE_UNIFORMS*/); ++i) {
+        var numActiveUniforms = GLctx.getProgramParameter(program, 0x8B86/*GL_ACTIVE_UNIFORMS*/);
+        for (var i = 0; i < numActiveUniforms; ++i) {
           program.maxUniformLength = Math.max(program.maxUniformLength, GLctx.getActiveUniform(program, i).name.length+1);
         }
       }
       {{{ makeSetValue('p', '0', 'program.maxUniformLength', 'i32') }}};
     } else if (pname == 0x8B8A /* GL_ACTIVE_ATTRIBUTE_MAX_LENGTH */) {
       if (!program.maxAttributeLength) {
-        for (var i = 0; i < GLctx.getProgramParameter(program, 0x8B89/*GL_ACTIVE_ATTRIBUTES*/); ++i) {
+        var numActiveAttributes = GLctx.getProgramParameter(program, 0x8B89/*GL_ACTIVE_ATTRIBUTES*/);
+        for (var i = 0; i < numActiveAttributes; ++i) {
           program.maxAttributeLength = Math.max(program.maxAttributeLength, GLctx.getActiveAttrib(program, i).name.length+1);
         }
       }
       {{{ makeSetValue('p', '0', 'program.maxAttributeLength', 'i32') }}};
     } else if (pname == 0x8A35 /* GL_ACTIVE_UNIFORM_BLOCK_MAX_NAME_LENGTH */) {
       if (!program.maxUniformBlockNameLength) {
-        for (var i = 0; i < GLctx.getProgramParameter(program, 0x8A36/*GL_ACTIVE_UNIFORM_BLOCKS*/); ++i) {
+        var numActiveUniformBlocks = GLctx.getProgramParameter(program, 0x8A36/*GL_ACTIVE_UNIFORM_BLOCKS*/);
+        for (var i = 0; i < numActiveUniformBlocks; ++i) {
           program.maxUniformBlockNameLength = Math.max(program.maxUniformBlockNameLength, GLctx.getActiveUniformBlockName(program, i).length+1);
         }
       }

diff --git a/test/code_size/embind_hello_wasm.json b/test/code_size/embind_hello_wasm.json
@@ -4,7 +4,7 @@
   "a.js": 9920,
   "a.js.gz": 4354,
   "a.wasm": 7715,
-  "a.wasm.gz": 3512,
+  "a.wasm.gz": 3508,
   "total": 18187,
-  "total_gz": 8246
+  "total_gz": 8242
 }
diff --git a/test/code_size/hello_webgl2_wasm.json b/test/code_size/hello_webgl2_wasm.json
@@ -1,10 +1,10 @@
 {
   "a.html": 454,
   "a.html.gz": 328,
-  "a.js": 4521,
-  "a.js.gz": 2308,
+  "a.js": 4531,
+  "a.js.gz": 2312,
   "a.wasm": 10399,
   "a.wasm.gz": 6695,
-  "total": 15374,
-  "total_gz": 9331
+  "total": 15384,
+  "total_gz": 9335
 }
diff --git a/test/code_size/hello_webgl2_wasm2js.json b/test/code_size/hello_webgl2_wasm2js.json
@@ -1,8 +1,8 @@
 {
   "a.html": 346,
   "a.html.gz": 262,
-  "a.js": 22193,
-  "a.js.gz": 11583,
-  "total": 22539,
-  "total_gz": 11845
+  "a.js": 22203,
+  "a.js.gz": 11588,
+  "total": 22549,
+  "total_gz": 11850
 }
diff --git a/test/code_size/hello_webgl_wasm.json b/test/code_size/hello_webgl_wasm.json
@@ -1,10 +1,10 @@
 {
   "a.html": 454,
   "a.html.gz": 328,
-  "a.js": 4059,
-  "a.js.gz": 2153,
+  "a.js": 4069,
+  "a.js.gz": 2158,
   "a.wasm": 10399,
   "a.wasm.gz": 6695,
-  "total": 14912,
-  "total_gz": 9176
+  "total": 14922,
+  "total_gz": 9181
 }
diff --git a/test/code_size/hello_webgl_wasm2js.json b/test/code_size/hello_webgl_wasm2js.json
@@ -1,8 +1,8 @@
 {
   "a.html": 346,
   "a.html.gz": 262,
-  "a.js": 21719,
-  "a.js.gz": 11419,
-  "total": 22065,
-  "total_gz": 11681
+  "a.js": 21729,
+  "a.js.gz": 11423,
+  "total": 22075,
+  "total_gz": 11685
 }
diff --git a/test/code_size/math_wasm.json b/test/code_size/math_wasm.json
@@ -4,7 +4,7 @@
   "a.js": 110,
   "a.js.gz": 125,
   "a.wasm": 2719,
-  "a.wasm.gz": 1674,
+  "a.wasm.gz": 1673,
   "total": 3381,
-  "total_gz": 2179
+  "total_gz": 2178
 }
diff --git a/test/code_size/random_printf_wasm.json b/test/code_size/random_printf_wasm.json
@@ -1,6 +1,6 @@
 {
   "a.html": 12690,
-  "a.html.gz": 6857,
+  "a.html.gz": 6855,
   "total": 12690,
-  "total_gz": 6857
+  "total_gz": 6855
 }
diff --git a/test/code_size/random_printf_wasm2js.json b/test/code_size/random_printf_wasm2js.json
@@ -1,6 +1,6 @@
 {
   "a.html": 17277,
-  "a.html.gz": 7489,
+  "a.html.gz": 7486,
   "total": 17277,
-  "total_gz": 7489
+  "total_gz": 7486
 }