The current GCC vectorizer requires the following pattern as a simple reduction computation:
loop_header: a1 = phi < a0, a2 > a3 = ... a2 = operation (a3, a1) But a3 can also be defined outside of the loop. For example, the following loop can benefit from vectorization but the GCC vectorizer fails to vectorize it: int foo(int v) { int s = 1; ++v; for (int i = 0; i < 100000; ++i) s *= v; return s; } This patch relaxes the original requirement by also considering the following pattern: a3 = ... loop_header: a1 = phi < a0, a2 > a2 = operation (a3, a1) A test case is also added. The patch is tested on x86-64. thanks, Cong ================================ diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 39c786e..45c1667 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2013-09-27 Cong Hou <co...@google.com> + + * tree-vect-loop.c: Relax the requirement of the reduction + pattern so that one operand of the reduction operation can + come from outside of the loop. + 2013-09-25 Tom Tromey <tro...@redhat.com> * Makefile.in (PARTITION_H, LTO_SYMTAB_H, COMMON_TARGET_DEF_H) diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 09644d2..90496a2 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,7 @@ +2013-09-27 Cong Hou <co...@google.com> + + * gcc.dg/vect/vect-reduc-pattern-3.c: New test. + 2013-09-25 Marek Polacek <pola...@redhat.com> PR sanitizer/58413 diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c index 2871ba1..3c51c3b 100644 --- a/gcc/tree-vect-loop.c +++ b/gcc/tree-vect-loop.c @@ -2091,6 +2091,13 @@ vect_is_slp_reduction (loop_vec_info loop_info, gimple phi, gimple first_stmt) a3 = ... a2 = operation (a3, a1) + or + + a3 = ... + loop_header: + a1 = phi < a0, a2 > + a2 = operation (a3, a1) + such that: 1. operation is commutative and associative and it is safe to change the order of the computation (if CHECK_REDUCTION is true) @@ -2451,6 +2458,7 @@ vect_is_simple_reduction_1 (loop_vec_info loop_info, gimple phi, if (def2 && def2 == phi && (code == COND_EXPR || !def1 || gimple_nop_p (def1) + || !flow_bb_inside_loop_p (loop, gimple_bb (def1)) || (def1 && flow_bb_inside_loop_p (loop, gimple_bb (def1)) && (is_gimple_assign (def1) || is_gimple_call (def1) @@ -2469,6 +2477,7 @@ vect_is_simple_reduction_1 (loop_vec_info loop_info, gimple phi, if (def1 && def1 == phi && (code == COND_EXPR || !def2 || gimple_nop_p (def2) + || !flow_bb_inside_loop_p (loop, gimple_bb (def2)) || (def2 && flow_bb_inside_loop_p (loop, gimple_bb (def2)) && (is_gimple_assign (def2) || is_gimple_call (def2) diff --git gcc/testsuite/gcc.dg/vect/vect-reduc-pattern-3.c gcc/testsuite/gcc.dg/vect/vect-reduc-pattern-3.c new file mode 100644 index 0000000..06a9416 --- /dev/null +++ gcc/testsuite/gcc.dg/vect/vect-reduc-pattern-3.c @@ -0,0 +1,41 @@ +/* { dg-require-effective-target vect_int } */ + +#include <stdarg.h> +#include "tree-vect.h" + +#define N 10 +#define RES 1024 + +/* A reduction pattern in which there is no data ref in + the loop and one operand is defined outside of the loop. */ + +__attribute__ ((noinline)) int +foo (int v) +{ + int i; + int result = 1; + + ++v; + for (i = 0; i < N; i++) + result *= v; + + return result; +} + +int +main (void) +{ + int res; + + check_vect (); + + res = foo (1); + if (res != RES) + abort (); + + return 0; +} + +/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" } } */ +/* { dg-final { cleanup-tree-dump "vect" } } */ +