From 3797b1083bd39e0072e07254b774bc27f1a68e2a Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Sat, 16 Nov 2024 19:25:20 +0900
Subject: [PATCH] [qfcc] Implement loops for spir-v

Mostly, at least: continue and break aren't functional yet, and for
loops haven't been tested, but while and do-while seem to work.
---
 tools/qfcc/include/expr.h        | 36 ++++++++++--
 tools/qfcc/include/expr_names.h  |  2 +
 tools/qfcc/source/expr.c         | 51 +++++++++++++++--
 tools/qfcc/source/expr_assign.c  |  2 +
 tools/qfcc/source/expr_dag.c     |  2 +
 tools/qfcc/source/expr_process.c | 39 +++++++++++++
 tools/qfcc/source/glsl-parse.y   | 33 +++++------
 tools/qfcc/source/target_spirv.c | 98 ++++++++++++++++++++++++++++++++
 8 files changed, 239 insertions(+), 24 deletions(-)

diff --git a/tools/qfcc/include/expr.h b/tools/qfcc/include/expr.h
index 62ea224db..ea18bad94 100644
--- a/tools/qfcc/include/expr.h
+++ b/tools/qfcc/include/expr.h
@@ -349,6 +349,23 @@ typedef struct {
 	symtab_t   *symtab;
 } ex_decl_t;
 
+typedef struct {
+	const expr_t *test;
+	const expr_t *body;
+	const expr_t *break_label;
+	const expr_t *continue_label;
+	bool        body_first;		///< true for do-while loops
+	bool        not;
+} ex_loop_t;
+
+typedef struct {
+	const expr_t *test;
+	const expr_t *true_body;
+	const expr_t *false_body;
+	rua_loc_t   els;
+	bool        not;
+} ex_select_t;
+
 typedef struct expr_s {
 	expr_t     *next;
 	rua_loc_t   loc;			///< source location of expression
@@ -395,6 +412,8 @@ typedef struct expr_s {
 		ex_field_t field;				///< field reference expression
 		ex_array_t array;				///< array index expression
 		ex_decl_t decl;					///< variable declaration expression
+		ex_loop_t loop;					///< loop construct expression
+		ex_select_t select;				///< selection construct expression
 	};
 } expr_t;
 
@@ -928,6 +947,14 @@ expr_t *new_decl_expr (specifier_t spec, symtab_t *symtab);
 expr_t *append_decl (expr_t *decl, symbol_t *sym, const expr_t *init);
 expr_t *append_decl_list (expr_t *decl, const expr_t *list);
 
+expr_t *new_loop_expr (bool not, bool body_first,
+					   const expr_t *test, const expr_t *body,
+					   const expr_t *break_label, const expr_t *continue_label);
+
+expr_t *new_select_expr (bool not, const expr_t *test,
+						 const expr_t *true_body,
+						 const expr_t *els, const expr_t *false_body);
+
 /**	Create an expression of the correct type that references the specified
 	parameter slot.
 
@@ -992,13 +1019,14 @@ const expr_t *deref_pointer_expr (const expr_t *pointer);
 const expr_t *pointer_deref (const expr_t *pointer);
 const expr_t *offset_pointer_expr (const expr_t *pointer, const expr_t *offset);
 const expr_t *address_expr (const expr_t *e1, const type_t *t);
-const expr_t *build_if_statement (int not, const expr_t *test, const expr_t *s1,
-								  const expr_t *els, const expr_t *s2);
-const expr_t *build_while_statement (int not, const expr_t *test,
+const expr_t *build_if_statement (bool not, const expr_t *test,
+								  const expr_t *s1, const expr_t *els,
+								  const expr_t *s2);
+const expr_t *build_while_statement (bool not, const expr_t *test,
 								     const expr_t *statement,
 								     const expr_t *break_label,
 								     const expr_t *continue_label);
-const expr_t *build_do_while_statement (const expr_t *statement, int not,
+const expr_t *build_do_while_statement (const expr_t *statement, bool not,
 										const expr_t *test,
 										const expr_t *break_label,
 										const expr_t *continue_label);
diff --git a/tools/qfcc/include/expr_names.h b/tools/qfcc/include/expr_names.h
index e0237b8ab..9bfae278a 100644
--- a/tools/qfcc/include/expr_names.h
+++ b/tools/qfcc/include/expr_names.h
@@ -74,6 +74,8 @@ EX_EXPR(cond)		///< ?: conditional expression (::ex_cond_t)
 EX_EXPR(field)		///< field reference expression (::ex_field_t)
 EX_EXPR(array)		///< array index expression (::ex_array_t)
 EX_EXPR(decl)		///< delcaration expression (::ex_array_t)
+EX_EXPR(loop)		///< loop construct expression (::ex_loop_t)
+EX_EXPR(select)		///< select construct expression (::ex_select_t)
 
 #undef EX_EXPR
 
diff --git a/tools/qfcc/source/expr.c b/tools/qfcc/source/expr.c
index 77b203113..206573ce2 100644
--- a/tools/qfcc/source/expr.c
+++ b/tools/qfcc/source/expr.c
@@ -145,6 +145,8 @@ get_type (const expr_t *e)
 			return nullptr;
 		case ex_return:
 		case ex_decl:
+		case ex_loop:
+		case ex_select:
 			internal_error (e, "unexpected expression type");
 		case ex_label:
 		case ex_compound:
@@ -996,7 +998,7 @@ new_ushort_expr (unsigned short ushort_val)
 bool
 is_error (const expr_t *e)
 {
-	return e->type == ex_error;
+	return e && e->type == ex_error;
 }
 
 bool
@@ -1979,6 +1981,8 @@ has_function_call (const expr_t *e)
 		case ex_args:
 		case ex_type:
 		case ex_decl:
+		case ex_loop:
+		case ex_select:
 			return false;
 		case ex_multivec:
 			for (auto c = e->multivec.components.head; c; c = c->next) {
@@ -2215,6 +2219,44 @@ new_decl_expr (specifier_t spec, symtab_t *symtab)
 	return decl;
 }
 
+expr_t *
+new_loop_expr (bool not, bool body_first,
+			   const expr_t *test, const expr_t *body,
+			   const expr_t *break_label, const expr_t *continue_label)
+{
+	auto loop = new_expr ();
+	loop->type = ex_loop;
+	loop->loop = (ex_loop_t) {
+		.test = test,
+		.body = body,
+		.break_label = break_label,
+		.continue_label = continue_label,
+		.body_first = body_first,
+		.not = not,
+	};
+	return loop;
+}
+
+expr_t *
+new_select_expr (bool not, const expr_t *test,
+				 const expr_t *true_body,
+				 const expr_t *els,
+				 const expr_t *false_body)
+{
+	auto select = new_expr ();
+	select->type = ex_select;
+	select->select = (ex_select_t) {
+		.test = test,
+		.true_body = true_body,
+		.false_body = false_body,
+		.not = not,
+	};
+	if (els) {
+		select->select.els = els->loc;
+	}
+	return select;
+}
+
 expr_t *
 append_decl (expr_t *decl, symbol_t *sym, const expr_t *init)
 {
@@ -2485,7 +2527,8 @@ address_expr (const expr_t *e1, const type_t *t)
 }
 
 const expr_t *
-build_if_statement (int not, const expr_t *test, const expr_t *s1, const expr_t *els, const expr_t *s2)
+build_if_statement (bool not, const expr_t *test, const expr_t *s1,
+					const expr_t *els, const expr_t *s2)
 {
 	expr_t     *if_expr;
 	expr_t     *tl = new_label_expr ();
@@ -2540,7 +2583,7 @@ build_if_statement (int not, const expr_t *test, const expr_t *s1, const expr_t
 }
 
 const expr_t *
-build_while_statement (int not, const expr_t *test, const expr_t *statement,
+build_while_statement (bool not, const expr_t *test, const expr_t *statement,
 					   const expr_t *break_label, const expr_t *continue_label)
 {
 	const expr_t *l1 = new_label_expr ();
@@ -2576,7 +2619,7 @@ build_while_statement (int not, const expr_t *test, const expr_t *statement,
 }
 
 const expr_t *
-build_do_while_statement (const expr_t *statement, int not, const expr_t *test,
+build_do_while_statement (const expr_t *statement, bool not, const expr_t *test,
 						  const expr_t *break_label,
 						  const expr_t *continue_label)
 {
diff --git a/tools/qfcc/source/expr_assign.c b/tools/qfcc/source/expr_assign.c
index 860b9aadf..66e329482 100644
--- a/tools/qfcc/source/expr_assign.c
+++ b/tools/qfcc/source/expr_assign.c
@@ -133,6 +133,8 @@ is_lvalue (const expr_t *expr)
 		case ex_type:
 		case ex_incop:
 		case ex_decl:
+		case ex_loop:
+		case ex_select:
 			break;
 		case ex_cond:
 			return (is_lvalue (expr->cond.true_expr)
diff --git a/tools/qfcc/source/expr_dag.c b/tools/qfcc/source/expr_dag.c
index 1840561a1..7b7788c65 100644
--- a/tools/qfcc/source/expr_dag.c
+++ b/tools/qfcc/source/expr_dag.c
@@ -80,6 +80,8 @@ edag_add_expr (const expr_t *expr)
 			case ex_type:
 			case ex_incop:
 			case ex_decl:
+			case ex_loop:
+			case ex_select:
 				// these are never put in the dag
 				return expr;
 			case ex_list:
diff --git a/tools/qfcc/source/expr_process.c b/tools/qfcc/source/expr_process.c
index 36d52425b..a4b42c66a 100644
--- a/tools/qfcc/source/expr_process.c
+++ b/tools/qfcc/source/expr_process.c
@@ -156,6 +156,12 @@ proc_field (const expr_t *expr)
 	return e;
 }
 
+static const expr_t *
+proc_label (const expr_t *expr)
+{
+	return expr;
+}
+
 static const expr_t *
 proc_block (const expr_t *expr)
 {
@@ -357,10 +363,41 @@ proc_decl (const expr_t *expr)
 	return block;
 }
 
+static const expr_t *
+proc_loop (const expr_t *expr)
+{
+	auto test = expr_process (expr->loop.test);
+	auto body = expr_process (expr->loop.body);
+	auto break_label = expr->loop.break_label;
+	auto continue_label = expr->loop.continue_label;
+	bool body_first = expr->loop.body_first;
+	bool not = expr->loop.not;
+	scoped_src_loc (expr);
+	return new_loop_expr (not, body_first, test, body,
+						  break_label, continue_label);
+}
+
+static const expr_t *
+proc_select (const expr_t *expr)
+{
+	auto test = expr_process (expr->select.test);
+	auto true_body = expr_process (expr->select.true_body);
+	auto false_body = expr_process (expr->select.false_body);
+	scoped_src_loc (expr);
+	auto select = new_select_expr (expr->select.not, test, true_body, nullptr,
+								   false_body);
+	select->select.els = expr->select.els;
+	return select;
+}
+
 const expr_t *
 expr_process (const expr_t *expr)
 {
+	if (!expr) {
+		return expr;
+	}
 	static process_f funcs[ex_count] = {
+		[ex_label] = proc_label,
 		[ex_block] = proc_block,
 		[ex_expr] = proc_expr,
 		[ex_uexpr] = proc_uexpr,
@@ -374,6 +411,8 @@ expr_process (const expr_t *expr)
 		[ex_cond] = proc_cond,
 		[ex_field] = proc_field,
 		[ex_decl] = proc_decl,
+		[ex_loop] = proc_loop,
+		[ex_select] = proc_select,
 	};
 
 	if (expr->type >= ex_count) {
diff --git a/tools/qfcc/source/glsl-parse.y b/tools/qfcc/source/glsl-parse.y
index c3050202b..644532fc5 100644
--- a/tools/qfcc/source/glsl-parse.y
+++ b/tools/qfcc/source/glsl-parse.y
@@ -1186,15 +1186,13 @@ expression_statement
 
 selection_statement
 //	: IF '(' expression ')' selection_rest_statement
-	: IF '(' expression ')' statement[true] %prec IFX
+	: IF '(' expression[test] ')' statement[true] %prec IFX
 		{
-			$$ = build_if_statement (false, $expression,
-									 $true, nullptr, nullptr);
+			$$ = new_select_expr (false, $test, $true, nullptr, nullptr);
 		}
-	| IF '(' expression ')' statement[true] else statement[false]
+	| IF '(' expression[test] ')' statement[true] else statement[false]
 		{
-			$$ = build_if_statement (false, $expression,
-									 $true, $else, $false);
+			$$ = new_select_expr (false, $test, $true, $else, $false);
 		}
 	;
 
@@ -1270,17 +1268,18 @@ iteration_statement
 	: WHILE new_scope break_label continue_label '(' condition ')'
 			  statement_no_new_scope
 		{
-			$$ = build_while_statement (false, $continue_label,
-										$statement_no_new_scope, break_label,
-										continue_label);
+			$$ = new_loop_expr (false, false,
+								$condition, $statement_no_new_scope,
+								break_label, continue_label);
 			break_label = $break_label;
 			continue_label = $continue_label;
 			current_symtab = $new_scope->block.scope->parent;
 		}
 	| DO break_label continue_label statement WHILE '(' expression ')' ';'
 		{
-			$$ = build_do_while_statement ($statement, false, $expression,
-										   break_label, continue_label);
+			$$ = new_loop_expr (false, true,
+								$expression, $statement,
+								break_label, continue_label);
 			break_label = $break_label;
 			continue_label = $continue_label;
 		}
@@ -1289,13 +1288,15 @@ iteration_statement
 			'(' for_init_statement conditionopt ';' expressionopt ')'
 			statement_no_new_scope
 		{
+			auto loop = new_loop_expr (false, false,
+									   $conditionopt, $statement_no_new_scope,
+									   break_label, continue_label);
+			auto block = new_block_expr (nullptr);
 			if ($for_init_statement) {
-				$for_init_statement = build_block_expr ((expr_t *) $for_init_statement,
-														false);
+				append_expr (block, $for_init_statement);
 			}
-			$$ = build_for_statement ($for_init_statement, $conditionopt,
-									  $expressionopt, $statement_no_new_scope,
-									  break_label, continue_label);
+			$$ = append_expr (block, loop);
+
 			break_label = $break_label;
 			continue_label = $continue_label;
 			current_symtab = $new_scope->block.scope->parent;
diff --git a/tools/qfcc/source/target_spirv.c b/tools/qfcc/source/target_spirv.c
index a40fcf9ec..35decbdb6 100644
--- a/tools/qfcc/source/target_spirv.c
+++ b/tools/qfcc/source/target_spirv.c
@@ -427,6 +427,7 @@ type_id (const type_t *type, spirvctx_t *ctx)
 	return id;
 }
 
+// put a label into decl_space. used only when starting a function
 static unsigned
 spirv_DeclLabel (spirvctx_t *ctx)
 {
@@ -443,6 +444,54 @@ spirv_Label (spirvctx_t *ctx)
 	return INSN (insn, 1);
 }
 
+static unsigned
+spirv_LabelId (unsigned id, spirvctx_t *ctx)
+{
+	auto insn = spirv_new_insn (SpvOpLabel, 2, ctx->code_space);
+	INSN (insn, 1) = id;
+	return id;
+}
+
+static void
+spirv_LoopMerge (unsigned merge, unsigned cont, spirvctx_t *ctx)
+{
+	auto insn = spirv_new_insn (SpvOpLoopMerge, 4, ctx->code_space);
+	INSN (insn, 1) = merge;
+	INSN (insn, 2) = cont;
+	INSN (insn, 3) = SpvLoopControlMaskNone;
+}
+
+static void
+spirv_Branch (unsigned label, spirvctx_t *ctx)
+{
+	auto insn = spirv_new_insn (SpvOpBranch, 2, ctx->code_space);
+	INSN (insn, 1) = label;
+}
+
+static unsigned
+spirv_SplitBlockId (unsigned id, spirvctx_t *ctx)
+{
+	spirv_Branch (id, ctx);
+	spirv_LabelId (id, ctx);
+	return id;
+}
+
+static unsigned
+spirv_SplitBlock (spirvctx_t *ctx)
+{
+	return spirv_SplitBlockId (spirv_id (ctx), ctx);
+}
+
+static void
+spirv_BranchConditional (unsigned test, unsigned true_label,
+						 unsigned false_label, spirvctx_t *ctx)
+{
+	auto insn = spirv_new_insn (SpvOpBranchConditional, 4, ctx->code_space);
+	INSN (insn, 1) = test;
+	INSN (insn, 2) = true_label;
+	INSN (insn, 3) = false_label;
+}
+
 static void
 spirv_Unreachable (spirvctx_t *ctx)
 {
@@ -1272,6 +1321,53 @@ spirv_field (const expr_t *e, spirvctx_t *ctx)
 	return id;
 }
 
+static unsigned
+spirv_loop (const expr_t *e, spirvctx_t *ctx)
+{
+	unsigned loop = spirv_id (ctx);
+	unsigned merge = spirv_id (ctx);
+	unsigned cont = spirv_id (ctx);
+	if (e->loop.body_first) {
+		spirv_Branch (loop, ctx);
+		spirv_LabelId (loop, ctx);
+		spirv_LoopMerge (merge, cont, ctx);
+		spirv_SplitBlock (ctx);
+		spirv_emit_expr (e->loop.body, ctx);
+		spirv_SplitBlockId (cont, ctx);
+		unsigned test = spirv_emit_expr (e->loop.test, ctx);
+		if (e->loop.not) {
+			spirv_BranchConditional (test, merge, loop, ctx);
+		} else {
+			spirv_BranchConditional (test, loop, merge, ctx);
+		}
+		spirv_LabelId (merge, ctx);
+	} else {
+		spirv_Branch (loop, ctx);
+		spirv_LabelId (loop, ctx);
+		spirv_LoopMerge (merge, cont, ctx);
+		spirv_SplitBlock (ctx);
+		unsigned body = spirv_id (ctx);
+		unsigned test = spirv_emit_expr (e->loop.test, ctx);
+		if (e->loop.not) {
+			spirv_BranchConditional (test, merge, body, ctx);
+		} else {
+			spirv_BranchConditional (test, body, merge, ctx);
+		}
+		spirv_LabelId (body, ctx);
+		spirv_emit_expr (e->loop.body, ctx);
+		spirv_SplitBlockId (cont, ctx);
+		spirv_Branch (loop, ctx);
+		spirv_LabelId (merge, ctx);
+	}
+	return 0;
+}
+
+static unsigned
+spirv_select (const expr_t *e, spirvctx_t *ctx)
+{
+	return 0;
+}
+
 static unsigned
 spirv_emit_expr (const expr_t *e, spirvctx_t *ctx)
 {
@@ -1288,6 +1384,8 @@ spirv_emit_expr (const expr_t *e, spirvctx_t *ctx)
 		[ex_extend] = spirv_extend,
 		[ex_cond] = spirv_cond,
 		[ex_field] = spirv_field,
+		[ex_loop] = spirv_loop,
+		[ex_select] = spirv_select,
 	};
 
 	if (e->type >= ex_count) {