Message ID | 5086FF8C.40209@redhat.com |
---|---|
State | New |
Headers | show |
On Tue, Oct 23, 2012 at 02:35:24PM -0600, Jeff Law wrote: > +/* Return TRUE if the statement at the end of e->dest depends on > + the output of any statement in BB. Otherwise return FALSE. > + > + This is used when we are threading a backedge and need to ensure > + that temporary equivalences from BB do not affect the condition > + in e->dest. */ > + > +static bool > +cond_arg_set_in_bb (edge e, basic_block bb, int n) > +{ > + ssa_op_iter iter; > + use_operand_p use_p; > + gimple last = gsi_stmt (gsi_last_bb (e->dest)); Use gimple last = last_stmt (e->dest); instead? That way any possible debug stmts are ignored. Jakub
On 10/23/2012 02:50 PM, Jakub Jelinek wrote: > On Tue, Oct 23, 2012 at 02:35:24PM -0600, Jeff Law wrote: >> +/* Return TRUE if the statement at the end of e->dest depends on >> + the output of any statement in BB. Otherwise return FALSE. >> + >> + This is used when we are threading a backedge and need to ensure >> + that temporary equivalences from BB do not affect the condition >> + in e->dest. */ >> + >> +static bool >> +cond_arg_set_in_bb (edge e, basic_block bb, int n) >> +{ >> + ssa_op_iter iter; >> + use_operand_p use_p; >> + gimple last = gsi_stmt (gsi_last_bb (e->dest)); > > Use gimple last = last_stmt (e->dest); instead? That way any possible > debug stmts are ignored. I thought I'd already dealt with this before. I'll double-check and take appropriate action. Any opinions about pulling it into 4.7.x as that release is affected by this codegen bug? I've got no strong opinions and I'm willing to pull it onto the branch if you want it. jeff
On Tue, Oct 23, 2012 at 03:21:59PM -0600, Jeff Law wrote: > On 10/23/2012 02:50 PM, Jakub Jelinek wrote: > >>+static bool > >>+cond_arg_set_in_bb (edge e, basic_block bb, int n) > >>+{ > >>+ ssa_op_iter iter; > >>+ use_operand_p use_p; > >>+ gimple last = gsi_stmt (gsi_last_bb (e->dest)); > > > >Use gimple last = last_stmt (e->dest); instead? That way any possible > >debug stmts are ignored. > I thought I'd already dealt with this before. I'll double-check and > take appropriate action. > > Any opinions about pulling it into 4.7.x as that release is affected > by this codegen bug? I've got no strong opinions and I'm willing to > pull it onto the branch if you want it. I think it should be backported to 4.7, perhaps with a few days delay after the trunk commit. Jakub
On 10/23/2012 03:22 PM, Jakub Jelinek wrote: > On Tue, Oct 23, 2012 at 03:21:59PM -0600, Jeff Law wrote: >> On 10/23/2012 02:50 PM, Jakub Jelinek wrote: >>>> +static bool >>>> +cond_arg_set_in_bb (edge e, basic_block bb, int n) >>>> +{ >>>> + ssa_op_iter iter; >>>> + use_operand_p use_p; >>>> + gimple last = gsi_stmt (gsi_last_bb (e->dest)); >>> >>> Use gimple last = last_stmt (e->dest); instead? That way any possible >>> debug stmts are ignored. >> I thought I'd already dealt with this before. I'll double-check and >> take appropriate action. >> >> Any opinions about pulling it into 4.7.x as that release is affected >> by this codegen bug? I've got no strong opinions and I'm willing to >> pull it onto the branch if you want it. > > I think it should be backported to 4.7, perhaps with a few days delay after the > trunk commit. Do we even have debug statements after control flow statements? jeff
On Tue, Oct 23, 2012 at 03:34:46PM -0600, Jeff Law wrote: > >I think it should be backported to 4.7, perhaps with a few days delay after the > >trunk commit. > Do we even have debug statements after control flow statements? They shouldn't be there, so if you just give up the same way for gsi_stmt NULL as well as non-control stmt, it shouldn't make a difference. So last_stmt might be just shorter to type and more commonly used, nothing more. Jakub
On 10/23/2012 03:43 PM, Jakub Jelinek wrote: > On Tue, Oct 23, 2012 at 03:34:46PM -0600, Jeff Law wrote: >>> I think it should be backported to 4.7, perhaps with a few days delay after the >>> trunk commit. >> Do we even have debug statements after control flow statements? > > They shouldn't be there, so if you just give up the same way for gsi_stmt > NULL as well as non-control stmt, it shouldn't make a difference. > So last_stmt might be just shorter to type and more commonly used, nothing > more. From looking at the existing code and last_stmt; for the cases we care about, they ought to be equivalent. Using last_stmt seems marginally clearer. I'll go ahead and make that change after the usual bootstrap & test cycle. jeff
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr54985.c b/gcc/testsuite/gcc.c-torture/execute/pr54985.c new file mode 100644 index 0000000..678c9f4 --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/execute/pr54985.c @@ -0,0 +1,36 @@ + +typedef struct st { + int a; +} ST; + +int __attribute__((noinline,noclone)) +foo(ST *s, int c) +{ + int first = 1; + int count = c; + ST *item = s; + int a = s->a; + int x; + + while (count--) + { + x = item->a; + if (first) + first = 0; + else if (x >= a) + return 1; + a = x; + item++; + } + return 0; +} + +extern void abort (void); + +int main () +{ + ST _1[2] = {{2}, {1}}; + if (foo(_1, 2) != 0) + abort (); + return 0; +} diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c index 105e3ab..491aa9f 100644 --- a/gcc/tree-ssa-threadedge.c +++ b/gcc/tree-ssa-threadedge.c @@ -572,6 +572,44 @@ simplify_control_stmt_condition (edge e, return cached_lhs; } +/* Return TRUE if the statement at the end of e->dest depends on + the output of any statement in BB. Otherwise return FALSE. + + This is used when we are threading a backedge and need to ensure + that temporary equivalences from BB do not affect the condition + in e->dest. */ + +static bool +cond_arg_set_in_bb (edge e, basic_block bb, int n) +{ + ssa_op_iter iter; + use_operand_p use_p; + gimple last = gsi_stmt (gsi_last_bb (e->dest)); + + /* E->dest does not have to end with a control transferring + instruction. This can occurr when we try to extend a jump + threading opportunity deeper into the CFG. In that case + it is safe for this check to return false. */ + if (!last) + return false; + + if (gimple_code (last) != GIMPLE_COND + && gimple_code (last) != GIMPLE_GOTO + && gimple_code (last) != GIMPLE_SWITCH) + return false; + + FOR_EACH_SSA_USE_OPERAND (use_p, last, iter, SSA_OP_USE | SSA_OP_VUSE) + { + tree use = USE_FROM_PTR (use_p); + + if (TREE_CODE (use) == SSA_NAME + && gimple_code (SSA_NAME_DEF_STMT (use)) != GIMPLE_PHI + && gimple_bb (SSA_NAME_DEF_STMT (use)) == bb) + return true; + } + return false; +} + /* TAKEN_EDGE represents the an edge taken as a result of jump threading. See if we can thread around TAKEN_EDGE->dest as well. If so, return the edge out of TAKEN_EDGE->dest that we can statically compute will be @@ -705,19 +743,8 @@ thread_across_edge (gimple dummy_cond, safe to thread this edge. */ if (e->flags & EDGE_DFS_BACK) { - ssa_op_iter iter; - use_operand_p use_p; - gimple last = gsi_stmt (gsi_last_bb (e->dest)); - - FOR_EACH_SSA_USE_OPERAND (use_p, last, iter, SSA_OP_USE | SSA_OP_VUSE) - { - tree use = USE_FROM_PTR (use_p); - - if (TREE_CODE (use) == SSA_NAME - && gimple_code (SSA_NAME_DEF_STMT (use)) != GIMPLE_PHI - && gimple_bb (SSA_NAME_DEF_STMT (use)) == e->dest) - goto fail; - } + if (cond_arg_set_in_bb (e, e->dest, 1)) + goto fail; } stmt_count = 0; @@ -758,7 +785,9 @@ thread_across_edge (gimple dummy_cond, address. If DEST is not null, then see if we can thread through it as well, this helps capture secondary effects of threading without having to re-run DOM or VRP. */ - if (dest) + if (dest + && ((e->flags & EDGE_DFS_BACK) == 0 + || ! cond_arg_set_in_bb (taken_edge, e->dest, 2))) { /* We don't want to thread back to a block we have already visited. This may be overly conservative. */ @@ -816,11 +845,16 @@ thread_across_edge (gimple dummy_cond, e3 = taken_edge; do { - e2 = thread_around_empty_block (e3, - dummy_cond, - handle_dominating_asserts, - simplify, - visited); + if ((e->flags & EDGE_DFS_BACK) == 0 + || ! cond_arg_set_in_bb (e3, e->dest, 3)) + e2 = thread_around_empty_block (e3, + dummy_cond, + handle_dominating_asserts, + simplify, + visited); + else + e2 = NULL; + if (e2) { e3 = e2;