Consider all callee_save_p regs as live on non trackable jumps

ChangeLog

@@ -1,3 +1,20 @@
+2014-09-07 Paulo Andrade <pcpa@gnu.org>
+
+	* lib/lightning.c: Mark all registers advertised as live, as
+	per jit_callee_save_p as live whenever reaching a jump that
+	cannot be tracked. This is a rethink of the previous commit,
+	and is a better approach, otherwise there would not be much
+	sense on relying on jit_callee_save_p if it could not be
+	trusted.
+
+	* check/jmpr.tst, check/jmpr.ok: New files implementing a very
+	simple test case, that would actually cause an assertion on
+	code before the change to only mark as live when reaching a
+	jump that could not tracked, the actually advertised as callee
+	save registers.
+
+	check/Makefile.am: Update for new jmpr test case.
+
 2014-09-01 Paulo Andrade <pcpa@gnu.org>
 
 	* lib/lightning.c: Do not mark all registers in unknown state

check/Makefile.am

@@ -77,6 +77,7 @@ EXTRA_DIST =				\
 	carry.tst	carry.ok	\
 	call.tst	call.ok		\
 	float.tst	float.ok	\
+	jmpr.tst	jmpr.ok		\
 	qalu.inc			\
 	qalu_mul.tst	qalu_mul.ok	\
 	qalu_div.tst	qalu_div.ok	\
@@ -104,7 +105,7 @@ base_TESTS =				\
 	fop_abs fop_sqrt		\
 	varargs stack			\
 	clobber carry call		\
-	float				\
+	float jmpr			\
 	qalu_mul qalu_div		\
 	ret
 
@@ -131,7 +132,7 @@ x87_TESTS =					\
 	fop_abs.x87 fop_sqrt.x87		\
 	varargs.x87 stack.x87			\
 	clobber.x87 carry.x87 call.x87		\
-	float.x87
+	float.x87 jmpr.x87
 $(x87_TESTS):	check.x87.sh
 	$(LN_S) $(srcdir)/check.x87.sh $@
 TESTS += $(x87_TESTS)
@@ -153,7 +154,7 @@ x87_nodata_TESTS =							\
 	fop_abs.x87.nodata fop_sqrt.x87.nodata				\
 	varargs.x87.nodata stack.x87.nodata				\
 	clobber.x87.nodata carry.x87.nodata call.x87.nodata		\
-	float.x87.nodata
+	float.x87.nodata jmpr.x87.nodata
 $(x87_nodata_TESTS):	check.x87.nodata.sh
 	$(LN_S) $(srcdir)/check.x87.nodata.sh $@
 TESTS += $(x87_nodata_TESTS)
@@ -177,7 +178,7 @@ arm_TESTS =					\
 	fop_abs.arm fop_sqrt.arm		\
 	varargs.arm stack.arm			\
 	clobber.arm carry.arm call.arm		\
-	float.arm
+	float.arm jmpr.arm
 $(arm_TESTS):	check.arm.sh
 	$(LN_S) $(srcdir)/check.arm.sh $@
 TESTS += $(arm_TESTS)
@@ -201,7 +202,7 @@ swf_TESTS =					\
 	fop_abs.swf fop_sqrt.swf		\
 	varargs.swf stack.swf			\
 	clobber.swf carry.swf call.swf		\
-	float.swf
+	float.swf jmpr.arm
 $(swf_TESTS):	check.swf.sh
 	$(LN_S) $(srcdir)/check.swf.sh $@
 TESTS += $(swf_TESTS)
@@ -225,7 +226,7 @@ nodata_TESTS =						\
 	fop_abs.nodata fop_sqrt.nodata			\
 	varargs.nodata stack.nodata			\
 	clobber.nodata carry.nodata call.nodata		\
-	float.nodata
+	float.nodata jmpr.nodata
 $(nodata_TESTS):	check.nodata.sh
 	$(LN_S) $(srcdir)/check.nodata.sh $@
 TESTS += $(nodata_TESTS)

check/jmpr.ok

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

check/jmpr.tst

@@ -0,0 +1,66 @@
+/*
+This is a very simple check to a condition that on lightning 2.0.5
+could cause an assertion on some backends, due to correcting a problem
+with temporaries that could not be saved/reloaded due to being used only
+in the hardware instruction, or being considered live for too long on the
+lightning instruction, and that could not be reloaded after the jump target
+(or after false/true target on conditional branches).
+
+If this code in lib/lightning.c:_jit_update():
+
+		    for (regno = 0; regno < _jitc->reglen; regno++) {
+			spec = jit_class(_rvs[regno].spec);
+			if (jit_regset_tstbit(mask, regno) &&
+			    (spec & (jit_class_gpr|jit_class_fpr)) &&
+			    !(spec & jit_class_sav))
+			    jit_regset_clrbit(mask, regno);
+		    }
+
+were removed, this test case, on x86_64 would fail like this:
+
+lt-lightning: lightning.c:305: _jit_get_reg: Assertion `regspec & 0x02000000' failed.
+Aborted (core dumped)
+ */
+
+.data	32
+ret:
+#if __WORDSIZE == 32
+.i	0
+#else
+.l	0
+#endif
+ok:
+.c	"ok"
+
+.code
+	prolog
+	jmpi start
+
+add_v1_v2:
+	addr %v1 %v1 %v2
+	ldi %r0 ret
+	jmpr %r0
+
+start:
+	movi %v1 1
+	movi %v2 2
+	movi %r0 ret_add_v1_v2
+	sti ret %r0
+	movi %v0 add_v1_v2
+	jmpr %v0
+	movi_d %f0 3
+	beqi_d pass_movi_f0 %f0 3
+	calli @abort
+pass_movi_f0:
+	beqi pass_check_v2 %v2 2
+	calli @abort
+pass_check_v2:
+ret_add_v1_v2:
+	beqi pass_add_v1_v2 %v1 3
+	calli @abort
+pass_add_v1_v2:
+	prepare
+		pushargi ok
+	finishi @puts
+	ret
+	epilog

lib/lightning.c

@@ -2172,19 +2172,9 @@ _jit_update(jit_state_t *_jit, jit_node_t *node,
 		     * no options for "nospill" temporaries (other temporaries
 		     * also benefit from not needing to spill/reload), so, the
 		     * user must ensure to either spill/reload, or only leave
-		     * live registers on JIT_Vn if using a jump that cannot
-		     * be tracked around the generated jit code */
-		    for (spec = JIT_R_NUM - 1; spec >= 0; spec--) {
-			regno = jit_r(spec);
-			if (jit_regset_tstbit(mask, regno))
-			    jit_regset_clrbit(mask, regno);
-		    }
-		    for (spec = JIT_F_NUM - 1; spec >= 0; spec--) {
-			regno = jit_f(spec);
-			if (jit_regset_tstbit(mask, regno))
-			    jit_regset_clrbit(mask, regno);
-		    }
-		    /* In some backends JIT_Rn and JIT_Fn are callee save */
+		     * live values on registers that are advertised as
+		     * callee save (as per jit_callee_save_p); on most targets
+		     * these are the JIT_Vn registers. */
 		    for (regno = 0; regno < _jitc->reglen; regno++) {
 			spec = jit_class(_rvs[regno].spec);
 			if (jit_regset_tstbit(mask, regno) &&