Put post-conditional assignments in a separate block

Author: davepagurek

src/strands/strands_conditionals.js

@@ -41,6 +41,7 @@ function buildConditional(strandsContext, conditional) {
   const mergeBlock = CFG.createBasicBlock(cfg, BlockType.MERGE);
   const results = [];
   const branchBlocks = [];
+  const branchEndBlocks = [];
   const mergedAssignments = {};
   const phiBlockDependencies = {};
   // Create a BRANCH block to handle phi node declarations
@@ -64,27 +65,28 @@ function buildConditional(strandsContext, conditional) {
     }
     const scopeStartBlock = CFG.createBasicBlock(cfg, BlockType.SCOPE_START);
     CFG.addEdge(cfg, previousBlock, scopeStartBlock);
-    const branchBlock = CFG.createBasicBlock(cfg, blockType);
-    CFG.addEdge(cfg, scopeStartBlock, branchBlock);
-    branchBlocks.push(branchBlock);
-    CFG.pushBlock(cfg, branchBlock);
+    const branchContentBlock = CFG.createBasicBlock(cfg, blockType);
+    CFG.addEdge(cfg, scopeStartBlock, branchContentBlock);
+    branchBlocks.push(branchContentBlock);
+    CFG.pushBlock(cfg, branchContentBlock);
     const branchResults = branchCallback();
     for (const key in branchResults) {
       if (!phiBlockDependencies[key]) {
-        phiBlockDependencies[key] = [{ value: branchResults[key], blockId: branchBlock }];
+        phiBlockDependencies[key] = [{ value: branchResults[key], blockId: branchContentBlock }];
       } else {
-        phiBlockDependencies[key].push({ value: branchResults[key], blockId: branchBlock });
+        phiBlockDependencies[key].push({ value: branchResults[key], blockId: branchContentBlock });
       }
     }
     results.push(branchResults);
+
+    // Create BRANCH_END block for phi assignments
+    const branchEndBlock = CFG.createBasicBlock(cfg, BlockType.DEFAULT);
+    CFG.addEdge(cfg, cfg.currentBlock, branchEndBlock);
+    branchEndBlocks.push(branchEndBlock);
+    CFG.popBlock(cfg);
+
     const scopeEndBlock = CFG.createBasicBlock(cfg, BlockType.SCOPE_END);
-    if (cfg.currentBlock !== branchBlock) {
-      CFG.addEdge(cfg, cfg.currentBlock, scopeEndBlock);
-      CFG.popBlock(cfg);
-    } else {
-      CFG.addEdge(cfg, branchBlock, scopeEndBlock);
-      CFG.popBlock(cfg);
-    }
+    CFG.addEdge(cfg, branchEndBlock, scopeEndBlock);
     CFG.addEdge(cfg, scopeEndBlock, mergeBlock);
     previousBlock = scopeStartBlock;
   }
@@ -96,8 +98,8 @@ function buildConditional(strandsContext, conditional) {
   CFG.popBlock(cfg);
   for (let i = 0; i < results.length; i++) {
     const branchResult = results[i];
-    const branchBlockID = branchBlocks[i];
-    CFG.pushBlockForModification(cfg, branchBlockID);
+    const branchEndBlockID = branchEndBlocks[i];
+    CFG.pushBlockForModification(cfg, branchEndBlockID);
     for (const key in branchResult) {
       if (mergedAssignments[key]) {
         // Create an assignment statement: phiNode = branchResult[key]
@@ -112,7 +114,7 @@ function buildConditional(strandsContext, conditional) {
           phiBlocks: []
         };
         const assignmentID = DAG.getOrCreateNode(strandsContext.dag, assignmentNode);
-        CFG.recordInBasicBlock(cfg, branchBlockID, assignmentID);
+        CFG.recordInBasicBlock(cfg, branchEndBlockID, assignmentID);
       }
     }
     CFG.popBlock(cfg);

test/unit/webgl/p5.Shader.js

@@ -596,6 +596,32 @@ suite('p5.Shader', function() {
         assert.approximately(pixelColor[1], 127, 5); // Green channel should be ~127
         assert.approximately(pixelColor[2], 127, 5); // Blue channel should be ~127
       });
+      test('handle if-else-if chains in the else branch', () => {
+        myp5.createCanvas(50, 50, myp5.WEBGL);
+        const testShader = myp5.baseMaterialShader().modify(() => {
+          const value = myp5.uniformFloat(() => 0.2); // middle value
+          myp5.getPixelInputs(inputs => {
+            let color = myp5.float(0.0);
+            if (value > 0.8) {
+              color = myp5.float(1.0); // white for high values
+            } else if (value > 0.3) {
+              color = myp5.float(0.5); // gray for medium values
+            } else {
+              color = myp5.float(0.0); // black for low values
+            }
+            inputs.color = [color, color, color, 1.0];
+            return inputs;
+          });
+        }, { myp5 });
+        myp5.noStroke();
+        myp5.shader(testShader);
+        myp5.plane(myp5.width, myp5.height);
+        // Check that the center pixel is gray (medium condition was true)
+        const pixelColor = myp5.get(25, 25);
+        assert.approximately(pixelColor[0], 0, 5); // Red channel should be ~127 (gray)
+        assert.approximately(pixelColor[1], 0, 5); // Green channel should be ~127
+        assert.approximately(pixelColor[2], 0, 5); // Blue channel should be ~127
+      });
       test('handle nested if statements', () => {
         myp5.createCanvas(50, 50, myp5.WEBGL);
         const testShader = myp5.baseMaterialShader().modify(() => {