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[qfcc] Add dependency edges for moved labels

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When moving an identifier label from one node to another, the first node
must be evaluated before the second node, which the edge guarantees.
However, code for swapping two variables

    t = a; a = b; b = t;

creates a dependency cycle. The solution is to create a new leaf node
for the source operand of the assignment. This fixes the swap.r test
without pessimizing postop code.

This takes care of the core problem in #3, but there is still room for
improvement in that the load/store can be combined into a move.
This commit is contained in:
Bill Currie 2021-06-29 12:56:23 +09:00
parent 76b3bedb72
commit a3aebc983b
3 changed files with 50 additions and 5 deletions
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25
tools/qfcc/source/dags.c
View file

@ -629,8 +629,8 @@ dag_make_var_live (set_t *live_vars, operand_t *op)
set_add (live_vars, var->number);
}
static void
dagnode_attach_label (dagnode_t *n, daglabel_t *l)
static int
dagnode_attach_label (dag_t *dag, dagnode_t *n, daglabel_t *l)
{
if (!l->op)
internal_error (0, "attempt to attach operator label to dagnode "
@ -641,9 +641,12 @@ dagnode_attach_label (dagnode_t *n, daglabel_t *l)
"identifiers");
if (l->dagnode) {
dagnode_t *node = l->dagnode;
set_union (n->edges, node->parents);
set_remove (n->edges, n->number);
set_remove (node->identifiers, l->number);
if (set_is_member (node->reachable, n->number)) {
return 0;
}
set_add (n->edges, node->number);
dagnode_set_reachable (dag, n);
}
l->live = 0; // remove live forcing on assignment
l->dagnode = n;
@ -652,6 +655,7 @@ dagnode_attach_label (dagnode_t *n, daglabel_t *l)
if (n->label->op) {
dag_live_aliases (n->label->op);
}
return 1;
}
static int
@ -848,7 +852,18 @@ dag_create (flownode_t *flownode)
lx = operand_label (dag, operands[0]);
if (lx && lx->dagnode != n) {
lx->expr = s->expr;
dagnode_attach_label (n, lx);
if (!dagnode_attach_label (dag, n, lx)) {
// attempting to attach the label to the node would create
// a dependency cycle in the dag, so a new node needs to be
// created for the source operand
if (s->type == st_assign) {
n = leaf_node (dag, operands[1], s->expr);
dagnode_attach_label (dag, n, lx);
} else {
internal_error (s->expr, "unexpected failure to attach"
" label to node");
}
}
}
if (n->type == st_ptrassign) {
dag_kill_nodes (dag, n);

11
tools/qfcc/test/Makemodule.am
View file

@ -32,6 +32,7 @@ test_progs_dat=\
tools/qfcc/test/nilparamret.dat \
tools/qfcc/test/overload.dat \
tools/qfcc/test/paramret.dat \
tools/qfcc/test/postop.dat \
tools/qfcc/test/quaternion.dat \
tools/qfcc/test/return-ivar.dat \
tools/qfcc/test/sendv.dat \
@ -372,6 +373,16 @@ tools/qfcc/test/paramret.run: $(qfcc_test_run_deps)
include $(paramret_dep) # am--include-marker
r_depfiles_remade += $(paramret_dep)
tools_qfcc_test_postop_dat_SOURCES=tools/qfcc/test/postop.r
postop_obj=$(tools_qfcc_test_postop_dat_SOURCES:.r=.o)
postop_dep=$(call qcautodep,$(tools_qfcc_test_postop_dat_SOURCES))
tools/qfcc/test/postop.dat$(EXEEXT): $(postop_obj) $(QFCC_DEP)
$(V_QFCCLD)$(QLINK) -o $@ $(postop_obj)
tools/qfcc/test/postop.run: $(qfcc_test_run_deps)
@$(top_srcdir)/tools/qfcc/test/build-run $@
include $(postop_dep) # am--include-marker
r_depfiles_remade += $(postop_dep)
tools_qfcc_test_quaternion_dat_SOURCES=tools/qfcc/test/quaternion.r
quaternion_obj=$(tools_qfcc_test_quaternion_dat_SOURCES:.r=.o)
quaternion_dep=$(call qcautodep,$(tools_qfcc_test_quaternion_dat_SOURCES))

19
tools/qfcc/test/postop.r Normal file
View file

@ -0,0 +1,19 @@
int array[3] = { -1, -1, -1 };
int array_index (void)
{
int i = 0;
for (int c = 0; c < 3; c++) {
array[i++] = 0;
}
return i == 3 && !(array[0] | array[1] | array[2]);
}
int
main ()
{
int ret = 0;
ret |= !array_index ();
return ret;
}