Implement the "live" code to explicitly tell a register is live.

*include/lightning.h, lib/lightning.c: Add the new jit_live code
	to explicitly mark a register as live. It is required to avoid
	assuming functions always return a value in the gpr and fpr return
	register, and to avoid the need of some very specialized codes
	that vary too much from backend to backend, to instruct the
	optimization code the return register is live.

	* lib/jit_arm.c, lib/jit_mips.c, lib/jit_ppc.c, lib/jit_print.c,
	lib/jit_x86.c: Update for the new jit_live code.

	* check/ret.ok, check/ret.tst: New files implementing a simple
	test case that would previously fail at least in ix86/x86_64.

	* check/Makefile.am: Update for new "ret" test case.

ChangeLog

@@ -1,3 +1,20 @@
+2013-02-05 Paulo Andrade <pcpa@gnu.org>
+
+	*include/lightning.h, lib/lightning.c: Add the new jit_live code
+	to explicitly mark a register as live. It is required to avoid
+	assuming functions always return a value in the gpr and fpr return
+	register, and to avoid the need of some very specialized codes
+	that vary too much from backend to backend, to instruct the
+	optimization code the return register is live.
+
+	* lib/jit_arm.c, lib/jit_mips.c, lib/jit_ppc.c, lib/jit_print.c,
+	lib/jit_x86.c: Update for the new jit_live code.
+
+	* check/ret.ok, check/ret.tst: New files implementing a simple
+	test case that would previously fail at least in ix86/x86_64.
+
+	* check/Makefile.am: Update for new "ret" test case.
+
 2013-02-05 Paulo Andrade <pcpa@gnu.org>
 
 	* lib/jit_ppc-cpu.c, lib/jit_ppc.c: Validate and correct

TODO

@@ -13,16 +13,6 @@
 	and "i" variants, and possibly unsigned version. Branches
 	would use "bo" and "bx" prefix.
 
-	* Convert retr to an actual node, otherwise, code like:
-	movi %r0 1
-	divr %r1 %r2 %r3
-	retr %r0
-	will fail in x86 because, besides "divr" telling it clobbers
-	%rax (r0) it ends being ignored because retr is a noop there
-	(removed "mov %rax,%rax" expansion) and the code checking for
-	live registers ends up not knowing about %rax being live after
-	the "divr". This affects only x86.
-
 	* Validate that divrem in jit_x86-cpu.c is not modifying
 	the non result arguments. This is not verified by clobber.tst,
 	as it only checks registers not involved in the operation

check/Makefile.am

@@ -69,6 +69,7 @@ EXTRA_DIST =				\
 	qalu.inc			\
 	qalu_mul.tst	qalu_mul.ok	\
 	qalu_div.tst	qalu_div.ok	\
+	ret.tst		ret.ok		\
 	ccall.ok			\
 	check.sh			\
 	check.x87.sh			\
@@ -92,7 +93,8 @@ base_TESTS =				\
 	varargs stack			\
 	clobber carry call		\
 	float				\
-	qalu_mul qalu_div
+	qalu_mul qalu_div		\
+	ret
 
 $(base_TESTS):	check.sh
 	$(LN_S) $(srcdir)/check.sh $@

check/ret.ok

@@ -0,0 +1 @@
+ok

check/ret.tst

@@ -0,0 +1,51 @@
+.data	16
+ok:
+.c	"ok"
+
+.code
+	jmpi main
+
+/*
+ * very simple test on purpose because otherwise it would not trigger
+ * the bug where the retr %r0 or retr_d %f0 would be omitted because
+ * the argument was already the return register, but the register end
+ * clobbered by another instruction, like the div*, and the wrong
+ * value returned because the retr* was removed and this way, lost
+ * information that the register was live at function exit.
+ */
+
+check_r0:
+	prolog
+	movi %r0 1
+	movi %r2 10
+	// on x86 this changes %rax on other arches could use %r0 as temporary
+	divi %r1 %r2 3
+	// %r0 must still be 1
+	retr %r0
+	epilog
+
+check_f0:
+	prolog
+	movi_d %f0 0.5
+	movi_d %f2 10
+	divi_d %f1 %f2 3
+	retr_d %f0
+	epilog
+
+main:
+	prolog
+	calli check_r0
+	retval %r1
+	beqi r0_ok %r1 1
+	calli @abort
+r0_ok:
+	calli check_f0
+	retval_d %f1
+	beqi_d f0_ok %f1 0.5
+	calli @abort
+f0_ok:
+	prepare
+		pushargi ok
+	finishi @puts
+	ret
+	epilog

include/lightning.h

@@ -101,6 +101,8 @@ typedef struct jit_state	jit_state_t;
 typedef enum {
 #define jit_data(u,v,w)		_jit_data(_jit,u,v,w)
     jit_code_data,
+#define jit_live(u)		jit_new_node_w(jit_code_live, u)
+    jit_code_live,
     jit_code_save,		jit_code_load,
 #define jit_name(u)		_jit_name(_jit,u)
     jit_code_name,

lib/jit_arm.c

@@ -278,7 +278,10 @@ _jit_ret(jit_state_t *_jit)
 void
 _jit_retr(jit_state_t *_jit, jit_int32_t u)
 {
-    jit_movr(JIT_RET, u);
+    if (JIT_RET != u)
+	jit_movr(JIT_RET, u);
+    else
+	jit_live(JIT_RET);
     jit_ret();
 }
 
@@ -295,20 +298,24 @@ _jit_retr_f(jit_state_t *_jit, jit_int32_t u)
     if (jit_cpu.abi) {
 	if (u != JIT_FRET)
 	    jit_movr_f(JIT_FRET, u);
+	else
+	    jit_live(JIT_FRET);
+    }
+    else {
+	if (u != JIT_RET)
+	    jit_movr_f_w(JIT_RET, u);
+	else
+	    jit_live(JIT_RET);
     }
-    else if (u != JIT_RET)
-	jit_movr_f_w(JIT_RET, u);
     jit_ret();
 }
 
 void
 _jit_reti_f(jit_state_t *_jit, jit_float32_t u)
 {
-    if (jit_cpu.abi) {
-	if (u != JIT_FRET)
-	    jit_movi_f(JIT_FRET, u);
-    }
-    else if (u != JIT_RET)
+    if (jit_cpu.abi)
+	jit_movi_f(JIT_FRET, u);
+    else
 	jit_movi_f_w(JIT_RET, u);
     jit_ret();
 }
@@ -319,20 +326,24 @@ _jit_retr_d(jit_state_t *_jit, jit_int32_t u)
     if (jit_cpu.abi) {
 	if (u != JIT_FRET)
 	    jit_movr_d(JIT_FRET, u);
+	else
+	    jit_live(JIT_FRET);
+    }
+    else {
+	if (u != JIT_RET)
+	    jit_movr_d_ww(JIT_RET, _R1, u);
+	else
+	    jit_live(JIT_RET);
     }
-    else if (u != JIT_RET)
-	jit_movr_d_ww(JIT_RET, _R1, u);
     jit_ret();
 }
 
 void
 _jit_reti_d(jit_state_t *_jit, jit_float64_t u)
 {
-    if (jit_cpu.abi) {
-	if (u != JIT_FRET)
-	    jit_movi_d(JIT_FRET, u);
-    }
-    else if (u != JIT_RET)
+    if (jit_cpu.abi)
+	jit_movi_d(JIT_FRET, u);
+    else
 	jit_movi_d_ww(JIT_RET, _R1, u);
     jit_ret();
 }
@@ -1476,6 +1487,7 @@ _emit_code(jit_state_t *_jit)
 		else
 		    vfp_movi_d(rn(node->u.w), node->w.d);
 		break;
+	    case jit_code_live:
 	    case jit_code_arg:
 	    case jit_code_arg_f:		case jit_code_arg_d:
 		break;

lib/jit_mips.c

@@ -187,14 +187,20 @@ _jit_retr(jit_state_t *_jit, jit_int32_t u)
 void
 _jit_reti(jit_state_t *_jit, jit_word_t u)
 {
-    jit_movi(JIT_RET, u);
+    if (JIT_RET != u)
+	jit_movi(JIT_RET, u);
+    else
+	jit_live(JIT_RET);
     jit_ret();
 }
 
 void
 _jit_retr_f(jit_state_t *_jit, jit_int32_t u)
 {
-    jit_movr_f(JIT_FRET, u);
+    if (JIT_FRET != u)
+	jit_movr_f(JIT_FRET, u);
+    else
+	jit_live(JIT_FRET);
     jit_ret();
 }
 
@@ -208,7 +214,10 @@ _jit_reti_f(jit_state_t *_jit, jit_float32_t u)
 void
 _jit_retr_d(jit_state_t *_jit, jit_int32_t u)
 {
-    jit_movr_d(JIT_FRET, u);
+    if (JIT_FRET != u)
+	jit_movr_d(JIT_FRET, u);
+    else
+	jit_live(JIT_FRET);
     jit_ret();
 }
 
@@ -1209,6 +1218,7 @@ _emit_code(jit_state_t *_jit)
 		movi_d_ww(rn(node->u.w), rn(node->v.w),
 			  (jit_float64_t *)node->w.n->u.w);
 		break;
+	    case jit_code_live:
 	    case jit_code_arg:
 	    case jit_code_arg_f:		case jit_code_arg_d:
 		break;

lib/jit_ppc.c

@@ -186,7 +186,10 @@ _jit_ret(jit_state_t *_jit)
 void
 _jit_retr(jit_state_t *_jit, jit_int32_t u)
 {
-    jit_movr(JIT_RET, u);
+    if (JIT_RET != u)
+	jit_movr(JIT_RET, u);
+    else
+	jit_live(JIT_RET);
     jit_ret();
 }
 
@@ -200,7 +203,10 @@ _jit_reti(jit_state_t *_jit, jit_word_t u)
 void
 _jit_retr_f(jit_state_t *_jit, jit_int32_t u)
 {
-    jit_movr_f(JIT_FRET, u);
+    if (JIT_RET != u)
+	jit_movr_f(JIT_FRET, u);
+    else
+	jit_live(JIT_FRET);
     jit_ret();
 }
 
@@ -214,7 +220,10 @@ _jit_reti_f(jit_state_t *_jit, jit_float32_t u)
 void
 _jit_retr_d(jit_state_t *_jit, jit_int32_t u)
 {
-    jit_movr_d(JIT_FRET, u);
+    if (JIT_FRET != u)
+	jit_movr_d(JIT_FRET, u);
+    else
+	jit_live(JIT_FRET);
     jit_ret();
 }
 
@@ -1188,6 +1197,7 @@ _emit_code(jit_state_t *_jit)
 		epilog(node);
 		_jit->function = NULL;
 		break;
+	    case jit_code_live:
 	    case jit_code_arg:
 	    case jit_code_arg_f:		case jit_code_arg_d:
 		break;

lib/jit_print.c

@@ -36,6 +36,7 @@
  */
 static char *code_name[] = {
     "data",
+    "live",
     "save",		"load",
     "#name",		"#note",
     "label",

lib/jit_x86.c

@@ -356,8 +356,12 @@ _jit_ret(jit_state_t *_jit)
 void
 _jit_retr(jit_state_t *_jit, jit_int32_t u)
 {
+    /* movr(%ret, %ret) would be optimized out */
     if (JIT_RET != u)
 	jit_movr(JIT_RET, u);
+    /* explicitly tell it is live */
+    else
+	jit_live(JIT_RET);
     jit_ret();
 }
 
@@ -373,6 +377,8 @@ _jit_retr_f(jit_state_t *_jit, jit_int32_t u)
 {
     if (JIT_FRET != u)
 	jit_movr_f(JIT_FRET, u);
+    else
+	jit_live(JIT_FRET);
     jit_ret();
 }
 
@@ -388,6 +394,8 @@ _jit_retr_d(jit_state_t *_jit, jit_int32_t u)
 {
     if (JIT_FRET != u)
 	jit_movr_d(JIT_FRET, u);
+    else
+	jit_live(JIT_FRET);
     jit_ret();
 }
 
@@ -1599,6 +1607,7 @@ _emit_code(jit_state_t *_jit)
 		    fstpr(rn(node->u.w) + 1);
 		break;
 #endif
+	    case jit_code_live:
 	    case jit_code_arg:
 	    case jit_code_arg_f:		case jit_code_arg_d:
 		break;

lib/lightning.c

@@ -809,6 +809,9 @@ _jit_classify(jit_state_t *_jit, jit_code_t code)
 	case jit_code_prolog:	case jit_code_epilog:
 	    mask = 0;
 	    break;
+	case jit_code_live:
+	    mask = jit_cc_a0_reg;
+	    break;
 	case jit_code_arg:	case jit_code_arg_f:	case jit_code_arg_d:
 	    mask = jit_cc_a0_int;
 	    break;