I was debugging a runtime failure of SPEC06 xalancbmk built with LIPO.
Using -fdisable-<pass> option pinpoints the problem in slp vectorize
pass on a particular function. dbgcnt support is added to to track
down the individual BB, but it fails even when the dbg count is set
to 0.
It turns out that no BB was actually vectorized for that function, but
turning on/off slp-vectorize does make a difference in generated code
-- the only difference between the good and bad case is stack layout.
The problem is in the alignment analysis phase -- which
speculatively changes the base declaration's alignment regardless
whether the vectorization transformation will be performed or not
later.
The attached patch fixes the problem. Testing is ok. Ok for trunk?
thanks,
David
Index: ChangeLog
===================================================================
--- ChangeLog (revision 202088)
+++ ChangeLog (working copy)
@@ -1,5 +1,17 @@
2013-08-29 Xinliang David Li <davi...@google.com>
+ * tree-vect-data-refs.c (vect_compute_data_ref_alignment):
+ Delay base decl alignment adjustment.
+ * tree-vectorizer.c (ensure_base_alignment): New function.
+ (vectorize_loops): Add dbg_cnt support. Perform alignment
+ adjustment.
+ (execute_vect_slp): Ditto.
+ * dbgcnt.def: New debug counter.
+ * tree-data-ref.h: New fields.
+ * Makefile: New dependency.
+
+2013-08-29 Xinliang David Li <davi...@google.com>
+
* loop-unroll.c (report_unroll_peel): Minor message
change.
* tree-vect-loop-manip.c (vect_do_peeling_for_alignment):
Index: tree-vect-data-refs.c
===================================================================
--- tree-vect-data-refs.c (revision 202088)
+++ tree-vect-data-refs.c (working copy)
@@ -763,15 +763,10 @@ vect_compute_data_ref_alignment (struct
dump_generic_expr (MSG_NOTE, TDF_SLIM, ref);
}
- DECL_ALIGN (base) = TYPE_ALIGN (vectype);
- DECL_USER_ALIGN (base) = 1;
+ DR_BASE_DECL (dr) = base;
+ DR_BASE_MISALIGNED (dr) = true;
}
- /* At this point we assume that the base is aligned. */
- gcc_assert (base_aligned
- || (TREE_CODE (base) == VAR_DECL
- && DECL_ALIGN (base) >= TYPE_ALIGN (vectype)));
-
/* If this is a backward running DR then first access in the larger
vectype actually is N-1 elements before the address in the DR.
Adjust misalign accordingly. */
Index: dbgcnt.def
===================================================================
--- dbgcnt.def (revision 202088)
+++ dbgcnt.def (working copy)
@@ -172,6 +172,8 @@ DEBUG_COUNTER (pre_insn)
DEBUG_COUNTER (treepre_insert)
DEBUG_COUNTER (tree_sra)
DEBUG_COUNTER (eipa_sra)
+DEBUG_COUNTER (vect_loop)
+DEBUG_COUNTER (vect_slp)
DEBUG_COUNTER (sched2_func)
DEBUG_COUNTER (sched_block)
DEBUG_COUNTER (sched_func)
Index: tree-vectorizer.c
===================================================================
--- tree-vectorizer.c (revision 202088)
+++ tree-vectorizer.c (working copy)
@@ -68,6 +68,7 @@ along with GCC; see the file COPYING3.
#include "tree-pass.h"
#include "hash-table.h"
#include "tree-ssa-propagate.h"
+#include "dbgcnt.h"
/* Loop or bb location. */
LOC vect_location;
@@ -279,6 +280,37 @@ note_simd_array_uses (hash_table <simd_a
}
}
+/* A helper function to enforce base alignment
+ before transforamtion. */
+
+static void
+ensure_base_alignment (loop_vec_info loop_vinfo, bb_vec_info bb_vinfo)
+{
+ vec<data_reference_p> datarefs;
+ struct data_reference *dr;
+ unsigned int i;
+
+ if (loop_vinfo)
+ datarefs = LOOP_VINFO_DATAREFS (loop_vinfo);
+ else
+ datarefs = BB_VINFO_DATAREFS (bb_vinfo);
+
+ FOR_EACH_VEC_ELT (datarefs, i, dr)
+ {
+ tree base_decl = DR_BASE_DECL (dr);
+ if (base_decl && DR_BASE_MISALIGNED (dr))
+ {
+ gimple stmt = DR_STMT (dr);
+ stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
+ tree vectype = STMT_VINFO_VECTYPE (stmt_info);
+ DECL_ALIGN (base_decl) = TYPE_ALIGN (vectype);
+ DECL_USER_ALIGN (base_decl) = 1;
+ DR_BASE_MISALIGNED (dr) = false;
+ }
+ }
+}
+
+
/* Function vectorize_loops.
Entry point to loop vectorization phase. */
@@ -331,10 +363,14 @@ vectorize_loops (void)
if (!loop_vinfo || !LOOP_VINFO_VECTORIZABLE_P (loop_vinfo))
continue;
+ if (!dbg_cnt (vect_loop))
+ break;
+
if (LOCATION_LOCUS (vect_location) != UNKNOWN_LOC
&& dump_enabled_p ())
dump_printf_loc (MSG_OPTIMIZED_LOCATIONS, vect_location,
"loop vectorized\n");
+ ensure_base_alignment (loop_vinfo, NULL);
vect_transform_loop (loop_vinfo);
num_vectorized_loops++;
/* Now that the loop has been vectorized, allow it to be unrolled
@@ -431,6 +467,7 @@ static unsigned int
execute_vect_slp (void)
{
basic_block bb;
+ bb_vec_info bb_vinfo;
init_stmt_vec_info_vec ();
@@ -438,8 +475,12 @@ execute_vect_slp (void)
{
vect_location = find_bb_location (bb);
- if (vect_slp_analyze_bb (bb))
+ if ((bb_vinfo = vect_slp_analyze_bb (bb)))
{
+ if (!dbg_cnt (vect_slp))
+ break;
+
+ ensure_base_alignment (NULL, bb_vinfo);
vect_slp_transform_bb (bb);
if (dump_enabled_p ())
dump_printf_loc (MSG_OPTIMIZED_LOCATIONS, vect_location,
Index: tree-data-ref.h
===================================================================
--- tree-data-ref.h (revision 202088)
+++ tree-data-ref.h (working copy)
@@ -176,6 +176,12 @@ struct data_reference
/* Auxiliary info specific to a pass. */
void *aux;
+ /* Base var decl. */
+ tree base_decl;
+
+ /* A boolean indicating if the base decl is misaligned. */
+ bool base_misaligned;
+
/* True when the data reference is in RHS of a stmt. */
bool is_read;
@@ -193,6 +199,8 @@ struct data_reference
};
#define DR_STMT(DR) (DR)->stmt
+#define DR_BASE_DECL(DR) (DR)->base_decl
+#define DR_BASE_MISALIGNED(DR) (DR)->base_misaligned
#define DR_REF(DR) (DR)->ref
#define DR_BASE_OBJECT(DR) (DR)->indices.base_object
#define DR_UNCONSTRAINED_BASE(DR) (DR)->indices.unconstrained_base
