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[PATCH, PR50769] Fix ICE in phi_alternatives_equal.
- From: Tom de Vries <Tom_deVries at mentor dot com>
- To: Richard Guenther <richard dot guenther at gmail dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 19 Oct 2011 11:23:31 +0300
- Subject: [PATCH, PR50769] Fix ICE in phi_alternatives_equal.
Richard,
For the example from the PR, -ftree-tail-merge discovers that blocks 6 and 7 are
equal, removes block 7 and redirects the outgoing edge of it's predecessor block
11 to block 6.
Block 6 contains a phi, which after redirecting the edge from block 11 looks
like this:
...
.MEM_54 = PHI <.MEM_27(18), .MEM_26(17), (11)>
...
Since update_vops is false, TODO_update_ssa_only_virtuals will be run
and -ftree-tail-merge doesn't update the phi.
However during cleanup_tree_cfg (which is done before updating the ssa),
phi_alternatives_equal is called which asserts that the phi arguments are defined.
The patch fixes the ICE by setting the empty phi argument to .MEM.
bootstrapped and reg-tested on x86_64.
Ok for trunk?
Thanks,
- Tom
2011-10-19 Tom de Vries <tom@codesourcery.com>
PR 50769/tree-optimization
* tree-ssa-tail-merge.c (replace_block_by): Calculate phi_vuse2
unconditionally. Handle case that phi_vuse2 is not an SSA_NAME. Add
dummy argument .MEM to phi when increasing number of arguments of phi by
redirecting edges to the block with phi.
Index: gcc/tree-ssa-tail-merge.c
===================================================================
--- gcc/tree-ssa-tail-merge.c (revision 179773)
+++ gcc/tree-ssa-tail-merge.c (working copy)
@@ -1470,11 +1470,14 @@ replace_block_by (basic_block bb1, basic
edge e;
edge_iterator ei;
+ phi_vuse2 = vop_at_entry (bb2);
+ if (phi_vuse2 != NULL_TREE && TREE_CODE (phi_vuse2) != SSA_NAME)
+ phi_vuse2 = NULL_TREE;
+
if (update_vops)
{
/* Find the vops at entry of bb1 and bb2. */
phi_vuse1 = vop_at_entry (bb1);
- phi_vuse2 = vop_at_entry (bb2);
/* If one of the 2 not found, it means there's no need to update. */
update_vops = phi_vuse1 != NULL_TREE && phi_vuse2 != NULL_TREE;
@@ -1507,6 +1510,9 @@ replace_block_by (basic_block bb1, basic
gcc_assert (pred_edge != NULL);
if (update_vops)
VEC_safe_push (edge, heap, redirected_edges, pred_edge);
+ else if (phi_vuse2 && gimple_bb (SSA_NAME_DEF_STMT (phi_vuse2)) == bb2)
+ add_phi_arg (SSA_NAME_DEF_STMT (phi_vuse2), SSA_NAME_VAR (phi_vuse2),
+ pred_edge, UNKNOWN_LOCATION);
}
/* Update the vops. */