shaderir: Allow specifying op for 'for' loop

internal/shaderir/glsl.go

@@ -177,14 +177,27 @@ func (p *Program) glslBlock(b *Block, f *Func, level int, localVarIndex int) []s
 			localVarIndex++
 			var delta string
 			switch s.ForDelta {
+			case 0:
+				delta = fmt.Sprintf("?(unexpected delta: %d)", s.ForDelta)
 			case 1:
 				delta = fmt.Sprintf("l%d++", v)
 			case -1:
 				delta = fmt.Sprintf("l%d--", v)
 			default:
+				if s.ForDelta > 0 {
 					delta = fmt.Sprintf("l%d += %d", v, s.ForDelta)
+				} else {
+					delta = fmt.Sprintf("l%d -= %d", v, -s.ForDelta)
 				}
-			lines = append(lines, fmt.Sprintf("%sfor (int l%d = %d; l%d < %d; %s) {", idt, v, s.ForInit, v, s.ForEnd, delta))
+			}
+			var op string
+			switch s.ForOp {
+			case LessThan, LessEqual, GreaterThan, GreaterEqual, Equal, NotEqual:
+				op = string(s.ForOp)
+			default:
+				op = fmt.Sprintf("?(unexpected op: %s)", string(s.ForOp))
+			}
+			lines = append(lines, fmt.Sprintf("%sfor (int l%d = %d; l%d %s %d; %s) {", idt, v, s.ForInit, v, op, s.ForEnd, delta))
 			lines = append(lines, p.glslBlock(&s.Blocks[0], f, level+1, localVarIndex)...)
 			lines = append(lines, fmt.Sprintf("%s}", idt))
 		case Continue:

internal/shaderir/ir_test.go

@@ -49,12 +49,13 @@ func ifStmt(cond Expr, block Block, elseBlock Block) Stmt {
 	}
 }
 
-func forStmt(init, end, delta int, block Block) Stmt {
+func forStmt(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,
 	}
 }
@@ -289,7 +290,7 @@ varying vec3 V0;`,
 							nil,
 							ifStmt(
 								binaryExpr(
-									Eq,
+									Equal,
 									varNameExpr(Local, 0),
 									floatExpr(0),
 								),
@@ -338,6 +339,7 @@ varying vec3 V0;`,
 							forStmt(
 								0,
 								100,
+								LessThan,
 								1,
 								block(
 									nil,

internal/shaderir/program.go

@@ -45,6 +45,7 @@ type Stmt struct {
 	Blocks   []Block
 	ForInit  int
 	ForEnd   int
+	ForOp    Op
 	ForDelta int
 }
 
@@ -109,18 +110,18 @@ const (
 	Mul          Op = "*"
 	Div          Op = "/"
 	Mod          Op = "%"
-	LShift Op = "<<"
+	LeftShift    Op = "<<"
-	RShift Op = ">>"
+	RightShift   Op = ">>"
-	LT     Op = "<"
+	LessThan     Op = "<"
-	LE     Op = "<="
+	LessEqual    Op = "<="
-	GT     Op = ">"
+	GreaterThan  Op = ">"
-	GE     Op = ">="
+	GreaterEqual Op = ">="
-	Eq     Op = "=="
+	Equal        Op = "=="
-	NE     Op = "!="
+	NotEqual     Op = "!="
 	And          Op = "&"
 	Xor          Op = "^"
 	Or           Op = "|"
 	AndAnd       Op = "&&"
 	OrOr         Op = "||"
-	Cond   Op = "?:"
+	Condition    Op = "?:"
 )