shader: Bug fix: Wrong local variable index in a block in the fragment entry point

internal/shader/shader.go

@@ -685,6 +685,7 @@ func (cs *compileState) parseBlock(outer *block, fname string, stmts []ast.Stmt,
 		if fname == cs.fragmentEntry {
 			offset-- // position
 			offset -= len(cs.ir.Varyings)
+			offset-- // color
 		}
 	}
 

internal/shader/testdata/for5.expected.fs

@@ -0,0 +1,34 @@
+uniform float U0;
+uniform float U1;
+uniform float U2;
+
+void F0(in int l0, out int l1);
+
+void F0(in int l0, out int l1) {
+	l1 = l0;
+	return;
+}
+
+void main(void) {
+	int l0 = 0;
+	int l2 = 0;
+	l0 = 0;
+	for (int l1 = 0; l1 < 10; l1++) {
+		int l2 = 0;
+		int l3 = 0;
+		F0(l1, l2);
+		l3 = l2;
+		l0 = (l0) + (l3);
+		for (int l4 = 0; l4 < 10; l4++) {
+			int l5 = 0;
+			int l6 = 0;
+			F0(l4, l5);
+			l6 = l5;
+			l0 = (l0) + (l6);
+		}
+	}
+	l2 = 0;
+	l0 = (l0) + (l2);
+	gl_FragColor = vec4(l0);
+	return;
+}

internal/shader/testdata/for5.go

@@ -24,3 +24,18 @@ func Vertex(pos vec2) vec4 {
 	sum += y
 	return vec4(sum)
 }
+
+func Fragment(pos vec4) vec4 {
+	sum := 0
+	for i := 0; i < 10; i++ {
+		x := Ident(i)
+		sum += x
+		for j := 0; j < 10; j++ {
+			x := Ident(j)
+			sum += x
+		}
+	}
+	y := 0
+	sum += y
+	return vec4(sum)
+}