First cut at new loop codegen.

SPIRV/GlslangToSpv.cpp

@@ -1342,33 +1342,51 @@ void TGlslangToSpvTraverser::visitConstantUnion(glslang::TIntermConstantUnion* n
 
 bool TGlslangToSpvTraverser::visitLoop(glslang::TVisit /* visit */, glslang::TIntermLoop* node)
 {
-    // body emission needs to know what the for-loop terminal is when it sees a "continue"
-    loopTerminal.push(node->getTerminal());
+    auto blocks = builder.makeNewLoop();
+    if (node->testFirst() && node->getTest()) {
+        spv::Block& head = builder.makeNewBlock();
+        builder.createBranch(&head);
 
-    builder.makeNewLoop(node->testFirst());
-
-    if (node->getTest()) {
+        builder.setBuildPoint(&head);
         node->getTest()->traverse(this);
-        // the AST only contained the test computation, not the branch, we have to add it
-        spv::Id condition = builder.accessChainLoad(convertGlslangToSpvType(node->getTest()->getType()));
-        builder.createLoopTestBranch(condition);
+        spv::Id condition =
+            builder.accessChainLoad(convertGlslangToSpvType(node->getTest()->getType()));
+        builder.createLoopMerge(&blocks.merge, &blocks.continue_target, spv::LoopControlMaskNone);
+        builder.createConditionalBranch(condition, &blocks.body, &blocks.merge);
+
+        builder.setBuildPoint(&blocks.body);
+        if (node->getBody())
+            node->getBody()->traverse(this);  // continue->cont, break->exit
+        builder.createBranch(&blocks.continue_target);
+
+        builder.setBuildPoint(&blocks.continue_target);
+        if (node->getTerminal())
+            node->getTerminal()->traverse(this);
+        builder.createBranch(&head);
     } else {
-        builder.createBranchToBody();
-    }
-
-    if (node->getBody()) {
-        breakForLoop.push(true);
-        node->getBody()->traverse(this);
-        breakForLoop.pop();
+        builder.createBranch(&blocks.body);
+
+        builder.setBuildPoint(&blocks.body);
+        if (node->getBody())
+            node->getBody()->traverse(this);  // continue->cont, break->exit
+        builder.createBranch(&blocks.continue_target);
+
+        builder.setBuildPoint(&blocks.continue_target);
+        if (node->getTerminal())
+            node->getTerminal()->traverse(this);
+        if (node->getTest()) {
+            node->getTest()->traverse(this);
+            spv::Id condition =
+                builder.accessChainLoad(convertGlslangToSpvType(node->getTest()->getType()));
+            builder.createLoopMerge(&blocks.merge, &blocks.continue_target,
+                                    spv::LoopControlMaskNone);
+            builder.createConditionalBranch(condition, &blocks.body, &blocks.merge);
+        } else {
+            builder.createBranch(&blocks.body);
+        }
     }
 
-    if (loopTerminal.top())
-        loopTerminal.top()->traverse(this);
-
-    builder.closeLoop();
-
-    loopTerminal.pop();
-
+    builder.setBuildPoint(&blocks.merge);
     return false;
 }
 

SPIRV/SpvBuilder.cpp

@@ -1753,6 +1753,19 @@ void Builder::endSwitch(std::vector<Block*>& /*segmentBlock*/)
     switchMerges.pop();
 }
 
+Block& Builder::makeNewBlock()
+{
+    Function& function = buildPoint->getParent();
+    auto block = new Block(getUniqueId(), function);
+    function.addBlock(block);
+    return *block;
+}
+
+Builder::LoopBlocks Builder::makeNewLoop()
+{
+    return {makeNewBlock(), makeNewBlock(), makeNewBlock()};
+}
+
 // Comments in header
 void Builder::makeNewLoop(bool loopTestFirst)
 {

SPIRV/SpvBuilder.h

@@ -378,6 +378,13 @@ public:
     // The loopTestFirst parameter is true when the loop test executes before
     // the body.  (It is false for do-while loops.)
     void makeNewLoop(bool loopTestFirst);
+    struct LoopBlocks {
+        Block &body, &merge, &continue_target;
+    };
+    LoopBlocks makeNewLoop();
+
+    // Create a new block in the function containing the build point.
+    Block& makeNewBlock();
 
     // Add the branch for the loop test, based on the given condition.
     // The true branch goes to the first block in the loop body, and
@@ -494,7 +501,11 @@ public:
 
     void dump(std::vector<unsigned int>&) const;
 
-protected:
+    void createBranch(Block* block);
+    void createConditionalBranch(Id condition, Block* thenBlock, Block* elseBlock);
+    void createLoopMerge(Block* mergeBlock, Block* continueBlock, unsigned int control);
+
+ protected:
     Id makeIntConstant(Id typeId, unsigned value, bool specConstant);
     Id findScalarConstant(Op typeClass, Op opcode, Id typeId, unsigned value) const;
     Id findScalarConstant(Op typeClass, Op opcode, Id typeId, unsigned v1, unsigned v2) const;
@@ -503,10 +514,7 @@ protected:
     void transferAccessChainSwizzle(bool dynamic);
     void simplifyAccessChainSwizzle();
     void createAndSetNoPredecessorBlock(const char*);
-    void createBranch(Block* block);
     void createSelectionMerge(Block* mergeBlock, unsigned int control);
-    void createLoopMerge(Block* mergeBlock, Block* continueBlock, unsigned int control);
-    void createConditionalBranch(Id condition, Block* thenBlock, Block* elseBlock);
     void dumpInstructions(std::vector<unsigned int>&, const std::vector<Instruction*>&) const;
 
     struct Loop; // Defined below.

Test/baseResults/spv.for-simple.vert.out

@@ -5,49 +5,51 @@ Linked vertex stage:
 
 // Module Version 10000
 // Generated by (magic number): 80001
-// Id's are bound by 25
+// Id's are bound by 26
 
                               Capability Shader
                1:             ExtInstImport  "GLSL.std.450"
                               MemoryModel Logical GLSL450
-                              EntryPoint Vertex 4  "main" 23 24
+                              EntryPoint Vertex 4  "main" 24 25
                               Source ESSL 300
                               Name 4  "main"
                               Name 8  "i"
-                              Name 17  "j"
-                              Name 23  "gl_VertexID"
-                              Name 24  "gl_InstanceID"
-                              Decorate 23(gl_VertexID) BuiltIn VertexId
-                              Decorate 24(gl_InstanceID) BuiltIn InstanceId
+                              Name 18  "j"
+                              Name 24  "gl_VertexID"
+                              Name 25  "gl_InstanceID"
+                              Decorate 24(gl_VertexID) BuiltIn VertexId
+                              Decorate 25(gl_InstanceID) BuiltIn InstanceId
                2:             TypeVoid
                3:             TypeFunction 2
                6:             TypeInt 32 1
                7:             TypePointer Function 6(int)
                9:      6(int) Constant 0
-              14:      6(int) Constant 10
-              15:             TypeBool
-              18:      6(int) Constant 12
-              20:      6(int) Constant 1
-              22:             TypePointer Input 6(int)
- 23(gl_VertexID):     22(ptr) Variable Input
-24(gl_InstanceID):     22(ptr) Variable Input
+              15:      6(int) Constant 10
+              16:             TypeBool
+              19:      6(int) Constant 12
+              21:      6(int) Constant 1
+              23:             TypePointer Input 6(int)
+ 24(gl_VertexID):     23(ptr) Variable Input
+25(gl_InstanceID):     23(ptr) Variable Input
          4(main):           2 Function None 3
                5:             Label
             8(i):      7(ptr) Variable Function
-           17(j):      7(ptr) Variable Function
+           18(j):      7(ptr) Variable Function
                               Store 8(i) 9
-                              Branch 10
+                              Branch 13
               10:             Label
-              13:      6(int) Load 8(i)
-              16:    15(bool) SLessThan 13 14
-                              LoopMerge 11 10 None
-                              BranchConditional 16 12 11
-              12:               Label
-                                Store 17(j) 18
-              19:      6(int)   Load 8(i)
-              21:      6(int)   IAdd 19 20
-                                Store 8(i) 21
-                                Branch 10
+                              Store 18(j) 19
+                              Branch 12
               11:             Label
                               Return
+              12:             Label
+              20:      6(int) Load 8(i)
+              22:      6(int) IAdd 20 21
+                              Store 8(i) 22
+                              Branch 13
+              13:             Label
+              14:      6(int) Load 8(i)
+              17:    16(bool) SLessThan 14 15
+                              LoopMerge 11 12 None
+                              BranchConditional 17 10 11
                               FunctionEnd