Re: [RFC] ldist: Recognize rawmemchr loop patterns

[Stefan Schulze Frielinghaus <stefansf@linux.ibm.com>]

ping

On Thu, Apr 08, 2021 at 10:23:31AM +0200, Stefan Schulze Frielinghaus wrote:
> ping
> 
> On Tue, Mar 16, 2021 at 06:13:21PM +0100, Stefan Schulze Frielinghaus wrote:
> > [snip]
> > 
> > Please find attached a new version of the patch.  A major change compared to
> > the previous patch is that I created a separate pass which hopefully makes
> > reviewing also easier since it is almost self-contained.  After realizing that
> > detecting loops which mimic the behavior of rawmemchr/strlen functions does not
> > really fit into the topic of loop distribution, I created a separate pass.  Due
> > to this I was also able to play around a bit and schedule the pass at different
> > times.  Currently it is scheduled right before loop distribution where loop
> > header copying already took place which leads to the following effect.  Running
> > this setup over
> > 
> > char *t (char *p)
> > {
> >   for (; *p; ++p);
> >   return p;
> > }
> > 
> > the new pass transforms
> > 
> > char * t (char * p)
> > {
> >   char _1;
> >   char _7;
> > 
> >   <bb 2> [local count: 118111600]:
> >   _7 = *p_3(D);
> >   if (_7 != 0)
> >     goto <bb 5>; [89.00%]
> >   else
> >     goto <bb 7>; [11.00%]
> > 
> >   <bb 5> [local count: 105119324]:
> > 
> >   <bb 3> [local count: 955630225]:
> >   # p_8 = PHI <p_6(6), p_3(D)(5)>
> >   p_6 = p_8 + 1;
> >   _1 = *p_6;
> >   if (_1 != 0)
> >     goto <bb 6>; [89.00%]
> >   else
> >     goto <bb 8>; [11.00%]
> > 
> >   <bb 8> [local count: 105119324]:
> >   # p_2 = PHI <p_6(3)>
> >   goto <bb 4>; [100.00%]
> > 
> >   <bb 6> [local count: 850510901]:
> >   goto <bb 3>; [100.00%]
> > 
> >   <bb 7> [local count: 12992276]:
> > 
> >   <bb 4> [local count: 118111600]:
> >   # p_9 = PHI <p_2(8), p_3(D)(7)>
> >   return p_9;
> > 
> > }
> > 
> > into
> > 
> > char * t (char * p)
> > {
> >   char * _5;
> >   char _7;
> > 
> >   <bb 2> [local count: 118111600]:
> >   _7 = *p_3(D);
> >   if (_7 != 0)
> >     goto <bb 5>; [89.00%]
> >   else
> >     goto <bb 4>; [11.00%]
> > 
> >   <bb 5> [local count: 105119324]:
> >   _5 = p_3(D) + 1;
> >   p_10 = .RAWMEMCHR (_5, 0);
> > 
> >   <bb 4> [local count: 118111600]:
> >   # p_9 = PHI <p_10(5), p_3(D)(2)>
> >   return p_9;
> > 
> > }
> > 
> > which is fine so far.  However, I haven't made up my mind so far whether it is
> > worthwhile to spend more time in order to also eliminate the "first unrolling"
> > of the loop.  I gave it a shot by scheduling the pass prior pass copy header
> > and ended up with:
> > 
> > char * t (char * p)
> > {
> >   <bb 2> [local count: 118111600]:
> >   p_5 = .RAWMEMCHR (p_3(D), 0);
> >   return p_5;
> > 
> > }
> > 
> > which seems optimal to me.  The downside of this is that I have to initialize
> > scalar evolution analysis which might be undesired that early.
> > 
> > All this brings me to the question where do you see this peace of code running?
> > If in a separate pass when would you schedule it?  If in an existing pass,
> > which one would you choose?
> > 
> > Another topic which came up is whether there exists a more elegant solution to
> > my current implementation in order to deal with stores (I'm speaking of the `if
> > (store_dr)` statement inside of function transform_loop_1).  For example,
> > 
> > extern char *p;
> > char *t ()
> > {
> >   for (; *p; ++p);
> >   return p;
> > }
> > 
> > ends up as
> > 
> > char * t ()
> > {
> >   char * _1;
> >   char * _2;
> >   char _3;
> >   char * p.1_8;
> >   char _9;
> >   char * p.1_10;
> >   char * p.1_11;
> > 
> >   <bb 2> [local count: 118111600]:
> >   p.1_8 = p;
> >   _9 = *p.1_8;
> >   if (_9 != 0)
> >     goto <bb 5>; [89.00%]
> >   else
> >     goto <bb 7>; [11.00%]
> > 
> >   <bb 5> [local count: 105119324]:
> > 
> >   <bb 3> [local count: 955630225]:
> >   # p.1_10 = PHI <_1(6), p.1_8(5)>
> >   _1 = p.1_10 + 1;
> >   p = _1;
> >   _3 = *_1;
> >   if (_3 != 0)
> >     goto <bb 6>; [89.00%]
> >   else
> >     goto <bb 8>; [11.00%]
> > 
> >   <bb 8> [local count: 105119324]:
> >   # _2 = PHI <_1(3)>
> >   goto <bb 4>; [100.00%]
> > 
> >   <bb 6> [local count: 850510901]:
> >   goto <bb 3>; [100.00%]
> > 
> >   <bb 7> [local count: 12992276]:
> > 
> >   <bb 4> [local count: 118111600]:
> >   # p.1_11 = PHI <_2(8), p.1_8(7)>
> >   return p.1_11;
> > 
> > }
> > 
> > where inside the loop a load and store occurs.  For a rawmemchr like loop I
> > have to show that we never load from a memory location to which we write.
> > Currently I solve this by hard coding those facts which are not generic at all.
> > I gave compute_data_dependences_for_loop a try which failed to determine the
> > fact that stores only happen to p[0] and loads from p[i] where i>0.  Maybe
> > there are more generic solutions to express this in contrast to my current one?
> > 
> > Thanks again for your input so far.  Really appreciated.
> > 
> > Cheers,
> > Stefan
> 
> > diff --git a/gcc/Makefile.in b/gcc/Makefile.in
> > index 8a5fb3fd99c..7b2d7405277 100644
> > --- a/gcc/Makefile.in
> > +++ b/gcc/Makefile.in
> > @@ -1608,6 +1608,7 @@ OBJS = \
> >  	tree-into-ssa.o \
> >  	tree-iterator.o \
> >  	tree-loop-distribution.o \
> > +	tree-loop-pattern.o \
> >  	tree-nested.o \
> >  	tree-nrv.o \
> >  	tree-object-size.o \
> > diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
> > index dd7173126fb..957e96a46a4 100644
> > --- a/gcc/internal-fn.c
> > +++ b/gcc/internal-fn.c
> > @@ -2917,6 +2917,33 @@ expand_VEC_CONVERT (internal_fn, gcall *)
> >    gcc_unreachable ();
> >  }
> >  
> > +void
> > +expand_RAWMEMCHR (internal_fn, gcall *stmt)
> > +{
> > +  expand_operand ops[3];
> > +
> > +  tree lhs = gimple_call_lhs (stmt);
> > +  if (!lhs)
> > +    return;
> > +  tree lhs_type = TREE_TYPE (lhs);
> > +  rtx lhs_rtx = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
> > +  create_output_operand (&ops[0], lhs_rtx, TYPE_MODE (lhs_type));
> > +
> > +  for (unsigned int i = 0; i < 2; ++i)
> > +    {
> > +      tree rhs = gimple_call_arg (stmt, i);
> > +      tree rhs_type = TREE_TYPE (rhs);
> > +      rtx rhs_rtx = expand_normal (rhs);
> > +      create_input_operand (&ops[i + 1], rhs_rtx, TYPE_MODE (rhs_type));
> > +    }
> > +
> > +  insn_code icode = direct_optab_handler (rawmemchr_optab, ops[2].mode);
> > +
> > +  expand_insn (icode, 3, ops);
> > +  if (!rtx_equal_p (lhs_rtx, ops[0].value))
> > +    emit_move_insn (lhs_rtx, ops[0].value);
> > +}
> > +
> >  /* Expand the IFN_UNIQUE function according to its first argument.  */
> >  
> >  static void
> > diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def
> > index daeace7a34e..95c76795648 100644
> > --- a/gcc/internal-fn.def
> > +++ b/gcc/internal-fn.def
> > @@ -348,6 +348,7 @@ DEF_INTERNAL_FN (MUL_OVERFLOW, ECF_CONST | ECF_LEAF | ECF_NOTHROW, NULL)
> >  DEF_INTERNAL_FN (TSAN_FUNC_EXIT, ECF_NOVOPS | ECF_LEAF | ECF_NOTHROW, NULL)
> >  DEF_INTERNAL_FN (VA_ARG, ECF_NOTHROW | ECF_LEAF, NULL)
> >  DEF_INTERNAL_FN (VEC_CONVERT, ECF_CONST | ECF_LEAF | ECF_NOTHROW, NULL)
> > +DEF_INTERNAL_FN (RAWMEMCHR, ECF_PURE | ECF_LEAF | ECF_NOTHROW, NULL)
> >  
> >  /* An unduplicable, uncombinable function.  Generally used to preserve
> >     a CFG property in the face of jump threading, tail merging or
> > diff --git a/gcc/optabs.def b/gcc/optabs.def
> > index b192a9d070b..f7c69f914ce 100644
> > --- a/gcc/optabs.def
> > +++ b/gcc/optabs.def
> > @@ -267,6 +267,7 @@ OPTAB_D (cpymem_optab, "cpymem$a")
> >  OPTAB_D (movmem_optab, "movmem$a")
> >  OPTAB_D (setmem_optab, "setmem$a")
> >  OPTAB_D (strlen_optab, "strlen$a")
> > +OPTAB_D (rawmemchr_optab, "rawmemchr$I$a")
> >  
> >  OPTAB_DC(fma_optab, "fma$a4", FMA)
> >  OPTAB_D (fms_optab, "fms$a4")
> > diff --git a/gcc/passes.def b/gcc/passes.def
> > index e9ed3c7bc57..280e8fc0cde 100644
> > --- a/gcc/passes.def
> > +++ b/gcc/passes.def
> > @@ -274,6 +274,7 @@ along with GCC; see the file COPYING3.  If not see
> >  	     empty loops.  Remove them now.  */
> >  	  NEXT_PASS (pass_cd_dce, false /* update_address_taken_p */);
> >  	  NEXT_PASS (pass_iv_canon);
> > +	  NEXT_PASS (pass_lpat);
> >  	  NEXT_PASS (pass_loop_distribution);
> >  	  NEXT_PASS (pass_linterchange);
> >  	  NEXT_PASS (pass_copy_prop);
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/lpat-rawmemchr-1.c b/gcc/testsuite/gcc.dg/tree-ssa/lpat-rawmemchr-1.c
> > new file mode 100644
> > index 00000000000..b4133510fca
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/lpat-rawmemchr-1.c
> > @@ -0,0 +1,72 @@
> > +/* { dg-do run { target s390x-*-* } } */
> > +/* { dg-options "-O2 -fdump-tree-lpat-details" } */
> > +/* { dg-final { scan-tree-dump-times "generated rawmemchrqi" 2 "lpat" { target s390x-*-* } } } */
> > +/* { dg-final { scan-tree-dump-times "generated rawmemchrhi" 2 "lpat" { target s390x-*-* } } } */
> > +/* { dg-final { scan-tree-dump-times "generated rawmemchrsi" 2 "lpat" { target s390x-*-* } } } */
> > +
> > +/* Rawmemchr pattern: reduction stmt but no store */
> > +
> > +#include <stdint.h>
> > +#include <assert.h>
> > +
> > +typedef __SIZE_TYPE__ size_t;
> > +extern void* malloc (size_t);
> > +extern void* memset (void*, int, size_t);
> > +
> > +#define test(T, pattern)   \
> > +__attribute__((noinline))  \
> > +T *test_##T (T *p)         \
> > +{                          \
> > +  while (*p != (T)pattern) \
> > +    ++p;                   \
> > +  return p;                \
> > +}
> > +
> > +test (uint8_t,  0xab)
> > +test (uint16_t, 0xabcd)
> > +test (uint32_t, 0xabcdef15)
> > +
> > +test (int8_t,  0xab)
> > +test (int16_t, 0xabcd)
> > +test (int32_t, 0xabcdef15)
> > +
> > +#define run(T, pattern, i)      \
> > +{                               \
> > +T *q = p;                       \
> > +q[i] = (T)pattern;              \
> > +assert (test_##T (p) == &q[i]); \
> > +q[i] = 0;                       \
> > +}
> > +
> > +int main(void)
> > +{
> > +  void *p = malloc (1024);
> > +  assert (p);
> > +  memset (p, 0, 1024);
> > +
> > +  run (uint8_t, 0xab, 0);
> > +  run (uint8_t, 0xab, 1);
> > +  run (uint8_t, 0xab, 13);
> > +
> > +  run (uint16_t, 0xabcd, 0);
> > +  run (uint16_t, 0xabcd, 1);
> > +  run (uint16_t, 0xabcd, 13);
> > +
> > +  run (uint32_t, 0xabcdef15, 0);
> > +  run (uint32_t, 0xabcdef15, 1);
> > +  run (uint32_t, 0xabcdef15, 13);
> > +
> > +  run (int8_t, 0xab, 0);
> > +  run (int8_t, 0xab, 1);
> > +  run (int8_t, 0xab, 13);
> > +
> > +  run (int16_t, 0xabcd, 0);
> > +  run (int16_t, 0xabcd, 1);
> > +  run (int16_t, 0xabcd, 13);
> > +
> > +  run (int32_t, 0xabcdef15, 0);
> > +  run (int32_t, 0xabcdef15, 1);
> > +  run (int32_t, 0xabcdef15, 13);
> > +
> > +  return 0;
> > +}
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/lpat-rawmemchr-2.c b/gcc/testsuite/gcc.dg/tree-ssa/lpat-rawmemchr-2.c
> > new file mode 100644
> > index 00000000000..9bebec11db0
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/lpat-rawmemchr-2.c
> > @@ -0,0 +1,83 @@
> > +/* { dg-do run { target s390x-*-* } } */
> > +/* { dg-options "-O2 -fdump-tree-lpat-details" } */
> > +/* { dg-final { scan-tree-dump-times "generated rawmemchrqi" 2 "lpat" { target s390x-*-* } } } */
> > +/* { dg-final { scan-tree-dump-times "generated rawmemchrhi" 2 "lpat" { target s390x-*-* } } } */
> > +/* { dg-final { scan-tree-dump-times "generated rawmemchrsi" 2 "lpat" { target s390x-*-* } } } */
> > +
> > +/* Rawmemchr pattern: reduction stmt and store */
> > +
> > +#include <stdint.h>
> > +#include <assert.h>
> > +
> > +typedef __SIZE_TYPE__ size_t;
> > +extern void* malloc (size_t);
> > +extern void* memset (void*, int, size_t);
> > +
> > +uint8_t *p_uint8_t;
> > +uint16_t *p_uint16_t;
> > +uint32_t *p_uint32_t;
> > +
> > +int8_t *p_int8_t;
> > +int16_t *p_int16_t;
> > +int32_t *p_int32_t;
> > +
> > +#define test(T, pattern)    \
> > +__attribute__((noinline))   \
> > +T *test_##T (void)          \
> > +{                           \
> > +  while (*p_##T != pattern) \
> > +    ++p_##T;                \
> > +  return p_##T;             \
> > +}
> > +
> > +test (uint8_t,  0xab)
> > +test (uint16_t, 0xabcd)
> > +test (uint32_t, 0xabcdef15)
> > +
> > +test (int8_t,  (int8_t)0xab)
> > +test (int16_t, (int16_t)0xabcd)
> > +test (int32_t, (int32_t)0xabcdef15)
> > +
> > +#define run(T, pattern, i) \
> > +{                          \
> > +T *q = p;                  \
> > +q[i] = pattern;            \
> > +p_##T = p;                 \
> > +T *r = test_##T ();        \
> > +assert (r == p_##T);       \
> > +assert (r == &q[i]);       \
> > +q[i] = 0;                  \
> > +}
> > +
> > +int main(void)
> > +{
> > +  void *p = malloc (1024);
> > +  assert (p);
> > +  memset (p, '\0', 1024);
> > +
> > +  run (uint8_t, 0xab, 0);
> > +  run (uint8_t, 0xab, 1);
> > +  run (uint8_t, 0xab, 13);
> > +
> > +  run (uint16_t, 0xabcd, 0);
> > +  run (uint16_t, 0xabcd, 1);
> > +  run (uint16_t, 0xabcd, 13);
> > +
> > +  run (uint32_t, 0xabcdef15, 0);
> > +  run (uint32_t, 0xabcdef15, 1);
> > +  run (uint32_t, 0xabcdef15, 13);
> > +
> > +  run (int8_t, (int8_t)0xab, 0);
> > +  run (int8_t, (int8_t)0xab, 1);
> > +  run (int8_t, (int8_t)0xab, 13);
> > +
> > +  run (int16_t, (int16_t)0xabcd, 0);
> > +  run (int16_t, (int16_t)0xabcd, 1);
> > +  run (int16_t, (int16_t)0xabcd, 13);
> > +
> > +  run (int32_t, (int32_t)0xabcdef15, 0);
> > +  run (int32_t, (int32_t)0xabcdef15, 1);
> > +  run (int32_t, (int32_t)0xabcdef15, 13);
> > +
> > +  return 0;
> > +}
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/lpat-strlen-1.c b/gcc/testsuite/gcc.dg/tree-ssa/lpat-strlen-1.c
> > new file mode 100644
> > index 00000000000..b02509c2c8c
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/lpat-strlen-1.c
> > @@ -0,0 +1,100 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-O2 -fdump-tree-lpat-details" } */
> > +/* { dg-final { scan-tree-dump-times "generated strlen\n" 4 "lpat" } } */
> > +/* { dg-final { scan-tree-dump-times "generated strlen using rawmemchrhi\n" 4 "lpat" { target s390x-*-* } } } */
> > +/* { dg-final { scan-tree-dump-times "generated strlen using rawmemchrsi\n" 4 "lpat" { target s390x-*-* } } } */
> > +
> > +#include <stdint.h>
> > +#include <assert.h>
> > +
> > +typedef __SIZE_TYPE__ size_t;
> > +extern void* malloc (size_t);
> > +extern void* memset (void*, int, size_t);
> > +
> > +#define test(T, U)        \
> > +__attribute__((noinline)) \
> > +U test_##T##U (T *s)      \
> > +{                         \
> > +  U i;                    \
> > +  for (i=0; s[i]; ++i);   \
> > +  return i;               \
> > +}
> > +
> > +test (uint8_t,  size_t)
> > +test (uint16_t, size_t)
> > +test (uint32_t, size_t)
> > +test (uint8_t,  int)
> > +test (uint16_t, int)
> > +test (uint32_t, int)
> > +
> > +test (int8_t,  size_t)
> > +test (int16_t, size_t)
> > +test (int32_t, size_t)
> > +test (int8_t,  int)
> > +test (int16_t, int)
> > +test (int32_t, int)
> > +
> > +#define run(T, U, i)             \
> > +{                                \
> > +T *q = p;                        \
> > +q[i] = 0;                        \
> > +assert (test_##T##U (p) == i);   \
> > +memset (&q[i], 0xf, sizeof (T)); \
> > +}
> > +
> > +int main(void)
> > +{
> > +  void *p = malloc (1024);
> > +  assert (p);
> > +  memset (p, 0xf, 1024);
> > +
> > +  run (uint8_t, size_t, 0);
> > +  run (uint8_t, size_t, 1);
> > +  run (uint8_t, size_t, 13);
> > +
> > +  run (int8_t, size_t, 0);
> > +  run (int8_t, size_t, 1);
> > +  run (int8_t, size_t, 13);
> > +
> > +  run (uint8_t, int, 0);
> > +  run (uint8_t, int, 1);
> > +  run (uint8_t, int, 13);
> > +
> > +  run (int8_t, int, 0);
> > +  run (int8_t, int, 1);
> > +  run (int8_t, int, 13);
> > +
> > +  run (uint16_t, size_t, 0);
> > +  run (uint16_t, size_t, 1);
> > +  run (uint16_t, size_t, 13);
> > +
> > +  run (int16_t, size_t, 0);
> > +  run (int16_t, size_t, 1);
> > +  run (int16_t, size_t, 13);
> > +
> > +  run (uint16_t, int, 0);
> > +  run (uint16_t, int, 1);
> > +  run (uint16_t, int, 13);
> > +
> > +  run (int16_t, int, 0);
> > +  run (int16_t, int, 1);
> > +  run (int16_t, int, 13);
> > +
> > +  run (uint32_t, size_t, 0);
> > +  run (uint32_t, size_t, 1);
> > +  run (uint32_t, size_t, 13);
> > +
> > +  run (int32_t, size_t, 0);
> > +  run (int32_t, size_t, 1);
> > +  run (int32_t, size_t, 13);
> > +
> > +  run (uint32_t, int, 0);
> > +  run (uint32_t, int, 1);
> > +  run (uint32_t, int, 13);
> > +
> > +  run (int32_t, int, 0);
> > +  run (int32_t, int, 1);
> > +  run (int32_t, int, 13);
> > +
> > +  return 0;
> > +}
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/lpat-strlen-2.c b/gcc/testsuite/gcc.dg/tree-ssa/lpat-strlen-2.c
> > new file mode 100644
> > index 00000000000..e71dad8ed2e
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/lpat-strlen-2.c
> > @@ -0,0 +1,58 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-O2 -fdump-tree-lpat-details" } */
> > +/* { dg-final { scan-tree-dump-times "generated strlen\n" 3 "lpat" } } */
> > +
> > +#include <assert.h>
> > +
> > +typedef __SIZE_TYPE__ size_t;
> > +extern void* malloc (size_t);
> > +extern void* memset (void*, int, size_t);
> > +
> > +__attribute__((noinline))
> > +int test_pos (char *s)
> > +{
> > +  int i;
> > +  for (i=42; s[i]; ++i);
> > +  return i;
> > +}
> > +
> > +__attribute__((noinline))
> > +int test_neg (char *s)
> > +{
> > +  int i;
> > +  for (i=-42; s[i]; ++i);
> > +  return i;
> > +}
> > +
> > +__attribute__((noinline))
> > +int test_including_null_char (char *s)
> > +{
> > +  int i;
> > +  for (i=1; s[i-1]; ++i);
> > +  return i;
> > +}
> > +
> > +int main(void)
> > +{
> > +  void *p = malloc (1024);
> > +  assert (p);
> > +  memset (p, 0xf, 1024);
> > +  char *s = (char *)p + 100;
> > +
> > +  s[42+13] = 0;
> > +  assert (test_pos (s) == 42+13);
> > +  s[42+13] = 0xf;
> > +
> > +  s[13] = 0;
> > +  assert (test_neg (s) == 13);
> > +  s[13] = 0xf;
> > +
> > +  s[-13] = 0;
> > +  assert (test_neg (s) == -13);
> > +  s[-13] = 0xf;
> > +
> > +  s[13] = 0;
> > +  assert (test_including_null_char (s) == 13+1);
> > +
> > +  return 0;
> > +}
> > diff --git a/gcc/timevar.def b/gcc/timevar.def
> > index 63c0b3306de..bdefc85fbb4 100644
> > --- a/gcc/timevar.def
> > +++ b/gcc/timevar.def
> > @@ -307,6 +307,7 @@ DEFTIMEVAR (TV_TREE_UBSAN            , "tree ubsan")
> >  DEFTIMEVAR (TV_INITIALIZE_RTL        , "initialize rtl")
> >  DEFTIMEVAR (TV_GIMPLE_LADDRESS       , "address lowering")
> >  DEFTIMEVAR (TV_TREE_LOOP_IFCVT       , "tree loop if-conversion")
> > +DEFTIMEVAR (TV_LPAT                  , "tree loop pattern")
> >  
> >  /* Everything else in rest_of_compilation not included above.  */
> >  DEFTIMEVAR (TV_EARLY_LOCAL	     , "early local passes")
> > diff --git a/gcc/tree-loop-distribution.c b/gcc/tree-loop-distribution.c
> > index 7ee19fc8677..f7aafd0d0dc 100644
> > --- a/gcc/tree-loop-distribution.c
> > +++ b/gcc/tree-loop-distribution.c
> > @@ -890,7 +890,7 @@ loop_distribution::partition_merge_into (struct graph *rdg,
> >  /* Returns true when DEF is an SSA_NAME defined in LOOP and used after
> >     the LOOP.  */
> >  
> > -static bool
> > +bool
> >  ssa_name_has_uses_outside_loop_p (tree def, loop_p loop)
> >  {
> >    imm_use_iterator imm_iter;
> > @@ -912,7 +912,7 @@ ssa_name_has_uses_outside_loop_p (tree def, loop_p loop)
> >  /* Returns true when STMT defines a scalar variable used after the
> >     loop LOOP.  */
> >  
> > -static bool
> > +bool
> >  stmt_has_scalar_dependences_outside_loop (loop_p loop, gimple *stmt)
> >  {
> >    def_operand_p def_p;
> > @@ -1234,7 +1234,7 @@ generate_memcpy_builtin (class loop *loop, partition *partition)
> >  
> >  /* Remove and destroy the loop LOOP.  */
> >  
> > -static void
> > +void
> >  destroy_loop (class loop *loop)
> >  {
> >    unsigned nbbs = loop->num_nodes;
> > diff --git a/gcc/tree-loop-pattern.c b/gcc/tree-loop-pattern.c
> > new file mode 100644
> > index 00000000000..a9c984d5e53
> > --- /dev/null
> > +++ b/gcc/tree-loop-pattern.c
> > @@ -0,0 +1,588 @@
> > +#include "config.h"
> > +#include "system.h"
> > +#include "coretypes.h"
> > +#include "backend.h"
> > +#include "intl.h"
> > +#include "tree.h"
> > +#include "gimple.h"
> > +#include "cfghooks.h"
> > +#include "tree-pass.h"
> > +#include "ssa.h"
> > +#include "fold-const.h"
> > +#include "gimple-iterator.h"
> > +#include "gimplify-me.h"
> > +#include "tree-cfg.h"
> > +#include "tree-ssa.h"
> > +#include "tree-ssanames.h"
> > +#include "tree-ssa-loop.h"
> > +#include "tree-ssa-loop-manip.h"
> > +#include "tree-into-ssa.h"
> > +#include "cfgloop.h"
> > +#include "tree-scalar-evolution.h"
> > +#include "tree-vectorizer.h"
> > +#include "tree-eh.h"
> > +#include "gimple-fold.h"
> > +#include "rtl.h"
> > +#include "memmodel.h"
> > +#include "insn-codes.h"
> > +#include "optabs.h"
> > +
> > +/* This pass detects loops which mimic the effects of builtins and replaces them
> > +   accordingly.  For example, a loop of the form
> > +
> > +     for (; *p != 42; ++p);
> > +
> > +   is replaced by
> > +
> > +     p = rawmemchr (p, 42);
> > +
> > +   under the assumption that rawmemchr is available for a particular mode.
> > +   Another example is
> > +
> > +     int i;
> > +     for (i = 42; s[i]; ++i);
> > +
> > +   which is replaced by
> > +
> > +     i = (int)strlen (&s[42]) + 42;
> > +
> > +   for some character array S.  In case array S is not of a character array
> > +   type, we end up with
> > +
> > +     i = (int)(rawmemchr (&s[42], 0) - &s[42]) + 42;
> > +
> > +   assuming that rawmemchr is available for a particular mode.  Note, detecting
> > +   strlen like loops also depends on whether the type for the resulting length
> > +   is compatible with size type or overflow is undefined.  */
> > +
> > +/* TODO Quick and dirty imports from tree-loop-distribution pass.  */
> > +void destroy_loop (class loop *loop);
> > +bool stmt_has_scalar_dependences_outside_loop (loop_p loop, gimple *stmt);
> > +bool ssa_name_has_uses_outside_loop_p (tree def, loop_p loop);
> > +
> > +static void
> > +generate_rawmemchr_builtin (loop_p loop, tree reduction_var,
> > +			    data_reference_p store_dr, tree base, tree pattern,
> > +			    location_t loc)
> > +{
> > +  gcc_checking_assert (POINTER_TYPE_P (TREE_TYPE (base))
> > +		       && TREE_TYPE (TREE_TYPE (base)) == TREE_TYPE (pattern));
> > +  gcc_checking_assert (TREE_TYPE (reduction_var) == TREE_TYPE (base));
> > +
> > +  /* The new statements will be placed before LOOP.  */
> > +  gimple_stmt_iterator gsi = gsi_last_bb (loop_preheader_edge (loop)->src);
> > +
> > +  tree mem = force_gimple_operand_gsi (&gsi, base, true, NULL_TREE, false,
> > +				       GSI_CONTINUE_LINKING);
> > +  gimple *fn_call = gimple_build_call_internal (IFN_RAWMEMCHR, 2, mem, pattern);
> > +  tree reduction_var_new = copy_ssa_name (reduction_var);
> > +  gimple_call_set_lhs (fn_call, reduction_var_new);
> > +  gimple_set_location (fn_call, loc);
> > +  gsi_insert_after (&gsi, fn_call, GSI_CONTINUE_LINKING);
> > +
> > +  if (store_dr)
> > +    {
> > +      gassign *g = gimple_build_assign (DR_REF (store_dr), reduction_var_new);
> > +      gsi_insert_after (&gsi, g, GSI_CONTINUE_LINKING);
> > +    }
> > +
> > +  imm_use_iterator iter;
> > +  gimple *stmt;
> > +  use_operand_p use_p;
> > +  FOR_EACH_IMM_USE_STMT (stmt, iter, reduction_var)
> > +    {
> > +      FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
> > +	SET_USE (use_p, reduction_var_new);
> > +
> > +      update_stmt (stmt);
> > +    }
> > +
> > +  fold_stmt (&gsi);
> > +
> > +  if (dump_file && (dump_flags & TDF_DETAILS))
> > +    switch (TYPE_MODE (TREE_TYPE (pattern)))
> > +      {
> > +      case QImode:
> > +	fprintf (dump_file, "generated rawmemchrqi\n");
> > +	break;
> > +
> > +      case HImode:
> > +	fprintf (dump_file, "generated rawmemchrhi\n");
> > +	break;
> > +
> > +      case SImode:
> > +	fprintf (dump_file, "generated rawmemchrsi\n");
> > +	break;
> > +
> > +      default:
> > +	gcc_unreachable ();
> > +      }
> > +}
> > +
> > +static void
> > +generate_strlen_builtin (loop_p loop, tree reduction_var, tree base,
> > +			 tree start_len, location_t loc)
> > +{
> > +  gcc_checking_assert (POINTER_TYPE_P (TREE_TYPE (base)));
> > +  gcc_checking_assert (TREE_TYPE (reduction_var) == TREE_TYPE (start_len));
> > +
> > +  /* The new statements will be placed before LOOP.  */
> > +  gimple_stmt_iterator gsi = gsi_last_bb (loop_preheader_edge (loop)->src);
> > +
> > +  tree reduction_var_new = make_ssa_name (size_type_node);
> > +
> > +  tree mem = force_gimple_operand_gsi (&gsi, base, true, NULL_TREE, false,
> > +				       GSI_CONTINUE_LINKING);
> > +  tree fn = build_fold_addr_expr (builtin_decl_implicit (BUILT_IN_STRLEN));
> > +  gimple *fn_call = gimple_build_call (fn, 1, mem);
> > +  gimple_call_set_lhs (fn_call, reduction_var_new);
> > +  gimple_set_location (fn_call, loc);
> > +  gsi_insert_after (&gsi, fn_call, GSI_CONTINUE_LINKING);
> > +
> > +  /* In case reduction type is not compatible with size type, then
> > +     conversion is sound even in case an overflow occurs since we previously
> > +     ensured that for reduction type an overflow is undefined.  */
> > +  tree convert = fold_convert (TREE_TYPE (reduction_var), reduction_var_new);
> > +  reduction_var_new = force_gimple_operand_gsi (&gsi, convert, true, NULL_TREE,
> > +						false, GSI_CONTINUE_LINKING);
> > +
> > +  /* Loops of the form `for (i=42; s[i]; ++i);` have an additional start
> > +     length.  */
> > +  if (!integer_zerop (start_len))
> > +    {
> > +      tree fn_result = reduction_var_new;
> > +      reduction_var_new = make_ssa_name (TREE_TYPE (reduction_var));
> > +      gimple *add_stmt = gimple_build_assign (reduction_var_new, PLUS_EXPR,
> > +					      fn_result, start_len);
> > +      gsi_insert_after (&gsi, add_stmt, GSI_CONTINUE_LINKING);
> > +    }
> > +
> > +  imm_use_iterator iter;
> > +  gimple *stmt;
> > +  use_operand_p use_p;
> > +  FOR_EACH_IMM_USE_STMT (stmt, iter, reduction_var)
> > +    {
> > +      FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
> > +	SET_USE (use_p, reduction_var_new);
> > +
> > +      update_stmt (stmt);
> > +    }
> > +
> > +  fold_stmt (&gsi);
> > +
> > +  if (dump_file && (dump_flags & TDF_DETAILS))
> > +    fprintf (dump_file, "generated strlen\n");
> > +}
> > +
> > +static void
> > +generate_strlen_builtin_using_rawmemchr (loop_p loop, tree reduction_var,
> > +					 tree base, tree start_len,
> > +					 location_t loc)
> > +{
> > +  gcc_checking_assert (POINTER_TYPE_P (TREE_TYPE (base)));
> > +  gcc_checking_assert (TREE_TYPE (reduction_var) == TREE_TYPE (start_len));
> > +
> > +  /* The new statements will be placed before LOOP.  */
> > +  gimple_stmt_iterator gsi = gsi_last_bb (loop_preheader_edge (loop)->src);
> > +
> > +  tree mem = force_gimple_operand_gsi (&gsi, base, true, NULL_TREE, false,
> > +				       GSI_CONTINUE_LINKING);
> > +  tree zero = build_zero_cst (TREE_TYPE (TREE_TYPE (mem)));
> > +  gimple *fn_call = gimple_build_call_internal (IFN_RAWMEMCHR, 2, mem, zero);
> > +  tree end = make_ssa_name (TREE_TYPE (base));
> > +  gimple_call_set_lhs (fn_call, end);
> > +  gimple_set_location (fn_call, loc);
> > +  gsi_insert_after (&gsi, fn_call, GSI_CONTINUE_LINKING);
> > +
> > +  tree diff = make_ssa_name (ptrdiff_type_node);
> > +  gimple *diff_stmt = gimple_build_assign (diff, POINTER_DIFF_EXPR, end, mem);
> > +  gsi_insert_after (&gsi, diff_stmt, GSI_CONTINUE_LINKING);
> > +
> > +  tree convert = fold_convert (ptrdiff_type_node,
> > +			       TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (mem))));
> > +  tree size = force_gimple_operand_gsi (&gsi, convert, true, NULL_TREE, false,
> > +					GSI_CONTINUE_LINKING);
> > +
> > +  tree count = make_ssa_name (ptrdiff_type_node);
> > +  gimple *count_stmt = gimple_build_assign (count, TRUNC_DIV_EXPR, diff, size);
> > +  gsi_insert_after (&gsi, count_stmt, GSI_CONTINUE_LINKING);
> > +
> > +  convert = fold_convert (TREE_TYPE (reduction_var), count);
> > +  tree reduction_var_new = force_gimple_operand_gsi (&gsi, convert, true,
> > +						     NULL_TREE, false,
> > +						     GSI_CONTINUE_LINKING);
> > +
> > +  /* Loops of the form `for (i=42; s[i]; ++i);` have an additional start
> > +     length.  */
> > +  if (!integer_zerop (start_len))
> > +    {
> > +      tree lhs = make_ssa_name (TREE_TYPE (reduction_var_new));
> > +      gimple *g = gimple_build_assign (lhs, PLUS_EXPR, reduction_var_new,
> > +				       start_len);
> > +      gsi_insert_after (&gsi, g, GSI_CONTINUE_LINKING);
> > +      reduction_var_new = lhs;
> > +    }
> > +
> > +  imm_use_iterator iter;
> > +  gimple *stmt;
> > +  use_operand_p use_p;
> > +  FOR_EACH_IMM_USE_STMT (stmt, iter, reduction_var)
> > +    {
> > +      FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
> > +	SET_USE (use_p, reduction_var_new);
> > +
> > +      update_stmt (stmt);
> > +    }
> > +
> > +  fold_stmt (&gsi);
> > +
> > +  if (dump_file && (dump_flags & TDF_DETAILS))
> > +    switch (TYPE_MODE (TREE_TYPE (zero)))
> > +      {
> > +      case HImode:
> > +	fprintf (dump_file, "generated strlen using rawmemchrhi\n");
> > +	break;
> > +
> > +      case SImode:
> > +	fprintf (dump_file, "generated strlen using rawmemchrsi\n");
> > +	break;
> > +
> > +      default:
> > +	gcc_unreachable ();
> > +      }
> > +}
> > +
> > +static bool
> > +transform_loop_1 (loop_p loop,
> > +		  data_reference_p load_dr,
> > +		  data_reference_p store_dr,
> > +		  tree reduction_var)
> > +{
> > +  tree load_ref = DR_REF (load_dr);
> > +  tree load_type = TREE_TYPE (load_ref);
> > +  tree load_access_base = build_fold_addr_expr (load_ref);
> > +  tree load_access_size = TYPE_SIZE_UNIT (load_type);
> > +  affine_iv load_iv, reduction_iv;
> > +  tree pattern;
> > +
> > +  /* A limitation of the current implementation is that we only support
> > +     constant patterns.  */
> > +  edge e = single_exit (loop);
> > +  gcond *cond_stmt = safe_dyn_cast <gcond *> (last_stmt (e->src));
> > +  if (!cond_stmt)
> > +    return false;
> > +  pattern = gimple_cond_rhs (cond_stmt);
> > +  if (gimple_cond_code (cond_stmt) != NE_EXPR
> > +      || gimple_cond_lhs (cond_stmt) != gimple_assign_lhs (DR_STMT (load_dr))
> > +      || TREE_CODE (pattern) != INTEGER_CST)
> > +    return false;
> > +
> > +  /* Bail out if no affine induction variable with constant step can be
> > +     determined.  */
> > +  if (!simple_iv (loop, loop, load_access_base, &load_iv, false))
> > +    return false;
> > +
> > +  /* Bail out if memory accesses are not consecutive or not growing.  */
> > +  if (!operand_equal_p (load_iv.step, load_access_size, 0))
> > +    return false;
> > +
> > +  if (!INTEGRAL_TYPE_P (load_type)
> > +      || !type_has_mode_precision_p (load_type))
> > +    return false;
> > +
> > +  if (!simple_iv (loop, loop, reduction_var, &reduction_iv, false))
> > +    return false;
> > +
> > +  /* Handle rawmemchr like loops.  */
> > +  if (operand_equal_p (load_iv.base, reduction_iv.base)
> > +      && operand_equal_p (load_iv.step, reduction_iv.step))
> > +    {
> > +      if (store_dr)
> > +	{
> > +	  /* Ensure that we store to X and load from X+I where I>0.  */
> > +	  if (TREE_CODE (load_iv.base) != POINTER_PLUS_EXPR
> > +	      || !integer_onep (TREE_OPERAND (load_iv.base, 1)))
> > +	    return false;
> > +	  tree ptr_base = TREE_OPERAND (load_iv.base, 0);
> > +	  if (TREE_CODE (ptr_base) != SSA_NAME)
> > +	    return false;
> > +	  gimple *def = SSA_NAME_DEF_STMT (ptr_base);
> > +	  if (!gimple_assign_single_p (def)
> > +	      || gimple_assign_rhs1 (def) != DR_REF (store_dr))
> > +	    return false;
> > +	  /* Ensure that the reduction value is stored.  */
> > +	  if (gimple_assign_rhs1 (DR_STMT (store_dr)) != reduction_var)
> > +	    return false;
> > +	}
> > +      /* Bail out if target does not provide rawmemchr for a certain mode.  */
> > +      machine_mode mode = TYPE_MODE (load_type);
> > +      if (direct_optab_handler (rawmemchr_optab, mode) == CODE_FOR_nothing)
> > +	return false;
> > +      location_t loc = gimple_location (DR_STMT (load_dr));
> > +      generate_rawmemchr_builtin (loop, reduction_var, store_dr, load_iv.base,
> > +				  pattern, loc);
> > +      return true;
> > +    }
> > +
> > +  /* Handle strlen like loops.  */
> > +  if (store_dr == NULL
> > +      && integer_zerop (pattern)
> > +      && TREE_CODE (reduction_iv.base) == INTEGER_CST
> > +      && TREE_CODE (reduction_iv.step) == INTEGER_CST
> > +      && integer_onep (reduction_iv.step)
> > +      && (types_compatible_p (TREE_TYPE (reduction_var), size_type_node)
> > +	  || TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (reduction_var))))
> > +    {
> > +      location_t loc = gimple_location (DR_STMT (load_dr));
> > +      if (TYPE_MODE (load_type) == TYPE_MODE (char_type_node)
> > +	  && TYPE_PRECISION (load_type) == TYPE_PRECISION (char_type_node))
> > +	generate_strlen_builtin (loop, reduction_var, load_iv.base,
> > +				 reduction_iv.base, loc);
> > +      else if (direct_optab_handler (rawmemchr_optab, TYPE_MODE (load_type))
> > +	       != CODE_FOR_nothing)
> > +	generate_strlen_builtin_using_rawmemchr (loop, reduction_var,
> > +						 load_iv.base,
> > +						 reduction_iv.base, loc);
> > +      else
> > +	return false;
> > +      if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (reduction_var)))
> > +	{
> > +	  const char *msg = G_("assuming signed overflow does not occur "
> > +			       "when optimizing strlen like loop");
> > +	  fold_overflow_warning (msg, WARN_STRICT_OVERFLOW_MISC);
> > +	}
> > +      return true;
> > +    }
> > +
> > +  return false;
> > +}
> > +
> > +static bool
> > +transform_loop (loop_p loop)
> > +{
> > +  gimple *reduction_stmt = NULL;
> > +  data_reference_p load_dr = NULL, store_dr = NULL;
> > +
> > +  basic_block *bbs = get_loop_body (loop);
> > +
> > +  for (unsigned i = 0, ninsns = 0; i < loop->num_nodes; ++i)
> > +    {
> > +      basic_block bb = bbs[i];
> > +
> > +      for (gphi_iterator bsi = gsi_start_phis (bb); !gsi_end_p (bsi);
> > +	   gsi_next (&bsi), ++ninsns)
> > +	{
> > +	  /* Bail out early for loops which are unlikely to match.  */
> > +	  if (ninsns > 16)
> > +	    return false;
> > +	  gphi *phi = bsi.phi ();
> > +	  if (gimple_has_volatile_ops (phi))
> > +	    return false;
> > +	  if (gimple_clobber_p (phi))
> > +	    continue;
> > +	  if (virtual_operand_p (gimple_phi_result (phi)))
> > +	    continue;
> > +	  if (stmt_has_scalar_dependences_outside_loop (loop, phi))
> > +	    {
> > +	      if (reduction_stmt)
> > +		return false;
> > +	      reduction_stmt = phi;
> > +	    }
> > +	}
> > +
> > +      for (gimple_stmt_iterator bsi = gsi_start_bb (bb); !gsi_end_p (bsi);
> > +	   gsi_next (&bsi), ++ninsns)
> > +	{
> > +	  /* Bail out early for loops which are unlikely to match.  */
> > +	  if (ninsns > 16)
> > +	    return false;
> > +
> > +	  gimple *stmt = gsi_stmt (bsi);
> > +
> > +	  if (gimple_clobber_p (stmt))
> > +	    continue;
> > +
> > +	  if (gimple_code (stmt) == GIMPLE_LABEL || is_gimple_debug (stmt))
> > +	    continue;
> > +
> > +	  if (gimple_has_volatile_ops (stmt))
> > +	    return false;
> > +
> > +	  if (stmt_has_scalar_dependences_outside_loop (loop, stmt))
> > +	    {
> > +	      if (reduction_stmt)
> > +		return false;
> > +	      reduction_stmt = stmt;
> > +	    }
> > +
> > +	  /* Any scalar stmts are ok.  */
> > +	  if (!gimple_vuse (stmt))
> > +	    continue;
> > +
> > +	  /* Otherwise just regular loads/stores.  */
> > +	  if (!gimple_assign_single_p (stmt))
> > +	    return false;
> > +
> > +	  auto_vec<data_reference_p, 2> dr_vec;
> > +	  if (!find_data_references_in_stmt (loop, stmt, &dr_vec))
> > +	    return false;
> > +	  data_reference_p dr;
> > +	  unsigned j;
> > +	  FOR_EACH_VEC_ELT (dr_vec, j, dr)
> > +	    {
> > +	      tree type = TREE_TYPE (DR_REF (dr));
> > +	      if (!ADDR_SPACE_GENERIC_P (TYPE_ADDR_SPACE (type)))
> > +		return false;
> > +	      if (DR_IS_READ (dr))
> > +		{
> > +		  if (load_dr != NULL)
> > +		    return false;
> > +		  load_dr = dr;
> > +		}
> > +	      else
> > +		{
> > +		  if (store_dr != NULL)
> > +		    return false;
> > +		  store_dr = dr;
> > +		}
> > +	    }
> > +	}
> > +    }
> > +
> > +  /* A limitation of the current implementation is that we require a reduction
> > +     statement which does not occur in cases like
> > +     extern int *p;
> > +     void foo (void) { for (; *p; ++p); } */
> > +  if (load_dr == NULL || reduction_stmt == NULL)
> > +    return false;
> > +
> > +  /* Note, reduction variables are guaranteed to be SSA names.  */
> > +  tree reduction_var;
> > +  switch (gimple_code (reduction_stmt))
> > +    {
> > +    case GIMPLE_PHI:
> > +      reduction_var = gimple_phi_result (reduction_stmt);
> > +      break;
> > +    case GIMPLE_ASSIGN:
> > +      reduction_var = gimple_assign_lhs (reduction_stmt);
> > +      break;
> > +    default:
> > +      /* Bail out e.g. for GIMPLE_CALL.  */
> > +      return false;
> > +    }
> > +  if (reduction_var == NULL)
> > +    return false;
> > +
> > +  /* Bail out if this is a bitfield memory reference.  */
> > +  if (TREE_CODE (DR_REF (load_dr)) == COMPONENT_REF
> > +      && DECL_BIT_FIELD (TREE_OPERAND (DR_REF (load_dr), 1)))
> > +    return false;
> > +
> > +  /* Data reference must be executed exactly once per iteration of each
> > +     loop in the loop nest.  We only need to check dominance information
> > +     against the outermost one in a perfect loop nest because a bb can't
> > +     dominate outermost loop's latch without dominating inner loop's.  */
> > +  basic_block load_bb = gimple_bb (DR_STMT (load_dr));
> > +  if (!dominated_by_p (CDI_DOMINATORS, loop->latch, load_bb))
> > +    return false;
> > +
> > +  if (store_dr)
> > +    {
> > +      /* Bail out if this is a bitfield memory reference.  */
> > +      if (TREE_CODE (DR_REF (store_dr)) == COMPONENT_REF
> > +	  && DECL_BIT_FIELD (TREE_OPERAND (DR_REF (store_dr), 1)))
> > +	return false;
> > +
> > +      /* Data reference must be executed exactly once per iteration of each
> > +	 loop in the loop nest.  We only need to check dominance information
> > +	 against the outermost one in a perfect loop nest because a bb can't
> > +	 dominate outermost loop's latch without dominating inner loop's.  */
> > +      basic_block store_bb = gimple_bb (DR_STMT (store_dr));
> > +      if (!dominated_by_p (CDI_DOMINATORS, loop->latch, store_bb))
> > +	return false;
> > +
> > +      /* Load and store must be in the same loop nest.  */
> > +      if (store_bb->loop_father != load_bb->loop_father)
> > +	return false;
> > +
> > +      edge e = single_exit (store_bb->loop_father);
> > +      if (!e)
> > +	return false;
> > +      bool load_dom = dominated_by_p (CDI_DOMINATORS, e->src, load_bb);
> > +      bool store_dom = dominated_by_p (CDI_DOMINATORS, e->src, store_bb);
> > +      if (load_dom != store_dom)
> > +	return false;
> > +    }
> > +
> > +  return transform_loop_1 (loop, load_dr, store_dr, reduction_var);
> > +}
> > +
> > +namespace {
> > +
> > +const pass_data pass_data_lpat =
> > +{
> > +  GIMPLE_PASS, /* type */
> > +  "lpat", /* name */
> > +  OPTGROUP_LOOP, /* optinfo_flags */
> > +  TV_LPAT, /* tv_id */
> > +  ( PROP_cfg | PROP_ssa ), /* properties_required */
> > +  0, /* properties_provided */
> > +  0, /* properties_destroyed */
> > +  0, /* todo_flags_start */
> > +  0, /* todo_flags_finish */
> > +};
> > +
> > +class pass_lpat : public gimple_opt_pass
> > +{
> > +public:
> > +  pass_lpat (gcc::context *ctxt)
> > +    : gimple_opt_pass (pass_data_lpat, ctxt)
> > +  {}
> > +
> > +  bool
> > +  gate (function *) OVERRIDE
> > +  {
> > +    return optimize != 0;
> > +  }
> > +
> > +  unsigned int
> > +  execute (function *f) OVERRIDE
> > +  {
> > +    loop_p loop;
> > +    auto_vec<loop_p> loops_to_be_destroyed;
> > +
> > +    FOR_EACH_LOOP_FN (f, loop, LI_ONLY_INNERMOST)
> > +      {
> > +	if (!single_exit (loop)
> > +	    || (!flag_tree_loop_distribute_patterns // TODO
> > +		&& !optimize_loop_for_speed_p (loop)))
> > +	continue;
> > +
> > +	if (transform_loop (loop))
> > +	  loops_to_be_destroyed.safe_push (loop);
> > +      }
> > +
> > +    if (loops_to_be_destroyed.length () > 0)
> > +      {
> > +	unsigned i;
> > +	FOR_EACH_VEC_ELT (loops_to_be_destroyed, i, loop)
> > +	  destroy_loop (loop);
> > +
> > +	scev_reset_htab ();
> > +	mark_virtual_operands_for_renaming (f);
> > +	rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa);
> > +
> > +	return TODO_cleanup_cfg;
> > +      }
> > +    else
> > +      return 0;
> > +  }
> > +}; // class pass_lpat
> > +
> > +} // anon namespace
> > +
> > +gimple_opt_pass *
> > +make_pass_lpat (gcc::context *ctxt)
> > +{
> > +  return new pass_lpat (ctxt);
> > +}
> > diff --git a/gcc/tree-pass.h b/gcc/tree-pass.h
> > index 15693fee150..2d71a12039e 100644
> > --- a/gcc/tree-pass.h
> > +++ b/gcc/tree-pass.h
> > @@ -380,6 +380,7 @@ extern gimple_opt_pass *make_pass_graphite (gcc::context *ctxt);
> >  extern gimple_opt_pass *make_pass_graphite_transforms (gcc::context *ctxt);
> >  extern gimple_opt_pass *make_pass_if_conversion (gcc::context *ctxt);
> >  extern gimple_opt_pass *make_pass_if_to_switch (gcc::context *ctxt);
> > +extern gimple_opt_pass *make_pass_lpat (gcc::context *ctxt);
> >  extern gimple_opt_pass *make_pass_loop_distribution (gcc::context *ctxt);
> >  extern gimple_opt_pass *make_pass_vectorize (gcc::context *ctxt);
> >  extern gimple_opt_pass *make_pass_simduid_cleanup (gcc::context *ctxt);
>