shaderir: Add Stmt.ForVarIndex

Updates #1230

internal/shaderir/glsl.go

@@ -364,8 +364,7 @@ func (p *Program) glslBlock(topBlock, block *Block, level int, localVarIndex int
 			}
 			lines = append(lines, fmt.Sprintf("%s}", idt))
 		case For:
-			v := localVarIndex
-			localVarIndex++
+			v := s.ForVarIndex
 			var delta string
 			switch s.ForDelta {
 			case 0:

internal/shaderir/ir_test.go

@@ -64,14 +64,15 @@ func ifStmt(cond Expr, block Block, elseBlock Block) Stmt {
 	}
 }
 
-func forStmt(init, end int, op Op, delta int, block Block) Stmt {
+func forStmt(index, init, end int, op Op, delta int, block Block) Stmt {
 	return Stmt{
-		Type:     For,
-		Blocks:   []Block{block},
-		ForInit:  init,
-		ForEnd:   end,
-		ForOp:    op,
-		ForDelta: delta,
+		Type:        For,
+		Blocks:      []Block{block},
+		ForVarIndex: index,
+		ForInit:     init,
+		ForEnd:      end,
+		ForOp:       op,
+		ForDelta:    delta,
 	}
 }
 
@@ -592,6 +593,7 @@ varying vec3 V0;`,
 						Block: block(
 							nil,
 							forStmt(
+								3,
 								0,
 								100,
 								LessThanOp,

internal/shaderir/program.go

@@ -64,13 +64,14 @@ type Block struct {
 }
 
 type Stmt struct {
-	Type     StmtType
-	Exprs    []Expr
-	Blocks   []Block
-	ForInit  int
-	ForEnd   int
-	ForOp    Op
-	ForDelta int
+	Type        StmtType
+	Exprs       []Expr
+	Blocks      []Block
+	ForVarIndex int
+	ForInit     int
+	ForEnd      int
+	ForOp       Op
+	ForDelta    int
 }
 
 type StmtType int