glslang -> SPV: 1) Include post switch-break unreachable blocks and 2) Generally, don't emit degenerate (basically empty) unreachable blocks.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@31023 e7fa87d3-cd2b-0410-9028-fcbf551c1848

SPIRV/SpvBuilder.cpp

@@ -1683,6 +1683,7 @@ void Builder::addSwitchBreak()
 {
     // branch to the top of the merge block stack
     createBranch(switchMerges.top());
+    createAndSetNoPredecessorBlock("post-switch-break");
 }
 
 // Comments in header
@@ -1993,11 +1994,12 @@ void Builder::simplifyAccessChainSwizzle()
 void Builder::createAndSetNoPredecessorBlock(const char* name)
 {
     Block* block = new Block(getUniqueId(), buildPoint->getParent());
+    block->setUnreachable();
     buildPoint->getParent().addBlock(block);
     setBuildPoint(block);
 
-    if (name)
+    //if (name)
-        addName(block->getId(), name);
+    //    addName(block->getId(), name);
 }
 
 // Comments in header

SPIRV/spvIR.h

@@ -162,8 +162,6 @@ protected:
 
 class Block {
 public:
-    // Setting insert to true indicates to add this new block 
-    // to the end of the parent function.
     Block(Id id, Function& parent);
     virtual ~Block()
     {
@@ -177,6 +175,8 @@ public:
     void addPredecessor(Block* pred) { predecessors.push_back(pred); }
     void addLocalVariable(Instruction* inst) { localVariables.push_back(inst); }
     int getNumPredecessors() const { return (int)predecessors.size(); }
+    void setUnreachable() { unreachable = true; }
+    bool isUnreachable() const { return unreachable; }
 
     bool isTerminated() const
     {
@@ -195,6 +195,12 @@ public:
 
     void dump(std::vector<unsigned int>& out) const
     {
+        // skip the degenerate unreachable blocks
+        // TODO: code gen: skip all unreachable blocks (transitive closure)
+        //                 (but, until that's done safer to keep non-degenerate unreachable blocks, in case others depend on something)
+        if (unreachable && instructions.size() <= 2)
+            return;
+
         instructions[0]->dump(out);
         for (int i = 0; i < (int)localVariables.size(); ++i)
             localVariables[i]->dump(out);
@@ -212,6 +218,11 @@ protected:
     std::vector<Block*> predecessors;
     std::vector<Instruction*> localVariables;
     Function& parent;
+
+    // track whether this block is known to be uncreachable (not necessarily 
+    // true for all unreachable blocks, but should be set at least
+    // for the extraneous ones introduced by the builder).
+    bool unreachable;
 };
 
 //
@@ -338,7 +349,7 @@ __inline void Function::addLocalVariable(Instruction* inst)
     parent.mapInstruction(inst);
 }
 
-__inline Block::Block(Id id, Function& parent) : parent(parent)
+__inline Block::Block(Id id, Function& parent) : parent(parent), unreachable(false)
 {
     instructions.push_back(new Instruction(id, NoType, OpLabel));
 }

Test/baseResults/switch.frag.out

@@ -17,7 +17,7 @@ ERROR: 0:120: 'default' : cannot appear outside switch statement
 ERROR: 0:126: 'onlyInSwitch' : undeclared identifier 
 WARNING: 0:128: 'switch' : last case/default label not followed by statements 
 ERROR: 0:140: 'nestedX' : undeclared identifier 
-ERROR: 0:156: 'nestedZ' : undeclared identifier 
+ERROR: 0:157: 'nestedZ' : undeclared identifier 
 ERROR: 17 compilation errors.  No code generated.
 
 
@@ -322,27 +322,28 @@ ERROR: node is still EOpNull!
 0:144              3 (const int)
 0:?           Sequence
 0:146            Branch: Break
-0:147          case:  with expression
+0:147            Branch: Break
-0:147            Constant:
+0:148          case:  with expression
-0:147              4 (const int)
+0:148            Constant:
+0:148              4 (const int)
 0:?           Sequence
-0:148            Sequence
+0:149            Sequence
-0:148              move second child to first child (temp mediump int)
+0:149              move second child to first child (temp mediump int)
-0:148                'linearY' (temp mediump int)
+0:149                'linearY' (temp mediump int)
-0:148                'linearZ' (temp mediump int)
+0:149                'linearZ' (temp mediump int)
-0:149            Branch: Break
+0:150            Branch: Break
-0:150          case:  with expression
+0:151          case:  with expression
-0:150            Constant:
+0:151            Constant:
-0:150              5 (const int)
+0:151              5 (const int)
-0:?           Sequence
-0:152            Branch: Break
-0:153          case:  with expression
-0:153            Constant:
-0:153              6 (const int)
 0:?           Sequence
+0:153            Branch: Break
+0:154          case:  with expression
 0:154            Constant:
-0:154              4 (const int)
+0:154              6 (const int)
-0:156      'nestedZ' (temp float)
+0:?           Sequence
+0:155            Constant:
+0:155              4 (const int)
+0:157      'nestedZ' (temp float)
 0:?   Linker Objects
 0:?     'c' (uniform mediump int)
 0:?     'd' (uniform mediump int)
@@ -653,27 +654,28 @@ ERROR: node is still EOpNull!
 0:144              3 (const int)
 0:?           Sequence
 0:146            Branch: Break
-0:147          case:  with expression
+0:147            Branch: Break
-0:147            Constant:
+0:148          case:  with expression
-0:147              4 (const int)
+0:148            Constant:
+0:148              4 (const int)
 0:?           Sequence
-0:148            Sequence
+0:149            Sequence
-0:148              move second child to first child (temp mediump int)
+0:149              move second child to first child (temp mediump int)
-0:148                'linearY' (temp mediump int)
+0:149                'linearY' (temp mediump int)
-0:148                'linearZ' (temp mediump int)
+0:149                'linearZ' (temp mediump int)
-0:149            Branch: Break
+0:150            Branch: Break
-0:150          case:  with expression
+0:151          case:  with expression
-0:150            Constant:
+0:151            Constant:
-0:150              5 (const int)
+0:151              5 (const int)
-0:?           Sequence
-0:152            Branch: Break
-0:153          case:  with expression
-0:153            Constant:
-0:153              6 (const int)
 0:?           Sequence
+0:153            Branch: Break
+0:154          case:  with expression
 0:154            Constant:
-0:154              4 (const int)
+0:154              6 (const int)
-0:156      'nestedZ' (temp float)
+0:?           Sequence
+0:155            Constant:
+0:155              4 (const int)
+0:157      'nestedZ' (temp float)
 0:?   Linker Objects
 0:?     'c' (uniform mediump int)
 0:?     'd' (uniform mediump int)

Test/switch.frag

@@ -144,6 +144,7 @@ void main()
     case 3:
         int linearZ;
         break;
+        break;
     case 4:
         int linearY = linearZ;
         break;