freedreno/afuc: Add iret

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6368>

src/freedreno/afuc/afuc.h

@@ -152,6 +152,11 @@ typedef union PACKED {
 		uint32_t uoff    : 26;    /* absolute (unsigned) offset */
 		uint32_t hdr     : 6;
 	} call;
+	struct PACKED {
+		uint32_t pad       : 25;
+		uint32_t interrupt : 1; /* return from ctxt-switch interrupt handler */
+		uint32_t hdr       : 6;
+	} ret;
 	struct PACKED {
 		uint32_t pad     : 26;
 		uint32_t hdr     : 6;

src/freedreno/afuc/asm.c

@@ -254,6 +254,10 @@ static void emit_instructions(int outfd)
 		case T_OP_RET:
 			opc = OPC_RET;
 			break;
+		case T_OP_IRET:
+			opc = OPC_RET;
+			instr.ret.interrupt = 1;
+			break;
 		case T_OP_CALL:
 			opc = OPC_CALL;
 			instr.call.uoff = resolve_label(ai->label);

src/freedreno/afuc/disasm.c

@@ -656,9 +656,12 @@ static void disasm(uint32_t *buf, int sizedwords)
 			break;
 		case OPC_RET:
 			assert(!rep);
-			if (instr->pad)
+			if (instr->ret.pad)
 				printf("[%08x]  ; ", instrs[i]);
-			printf("ret");
+			if (instr->ret.interrupt)
+				printf("iret");
+			else
+				printf("ret");
 			break;
 		case OPC_WIN:
 			assert(!rep);

src/freedreno/afuc/lexer.l

@@ -78,6 +78,7 @@ extern YYSTYPE yylval;
 "brne"                            return TOKEN(T_OP_BRNE);
 "breq"                            return TOKEN(T_OP_BREQ);
 "ret"                             return TOKEN(T_OP_RET);
+"iret"                            return TOKEN(T_OP_IRET);
 "call"                            return TOKEN(T_OP_CALL);
 "jump"                            return TOKEN(T_OP_JUMP);
 "waitin"                          return TOKEN(T_OP_WAITIN);

src/freedreno/afuc/parser.y

@@ -153,6 +153,7 @@ label(const char *str)
 %token <tok> T_OP_BRNE
 %token <tok> T_OP_BREQ
 %token <tok> T_OP_RET
+%token <tok> T_OP_IRET
 %token <tok> T_OP_CALL
 %token <tok> T_OP_JUMP
 %token <tok> T_OP_WAITIN
@@ -248,6 +249,7 @@ other_instr:       T_OP_CALL T_LABEL_REF { new_instr($1); label($2); }
 |                  T_OP_PREEMPTLEAVE T_LABEL_REF { new_instr($1); label($2); }
 |                  T_OP_SETSECURE reg ',' T_LABEL_REF { new_instr($1); src1($2); label($4); }
 |                  T_OP_RET              { new_instr($1); }
+|                  T_OP_IRET             { new_instr($1); }
 |                  T_OP_JUMP T_LABEL_REF { new_instr($1); label($2); }
 |                  T_OP_WAITIN           { new_instr($1); }
 |                  T_OP_NOP              { new_instr($1); }