[GIMPLE,FE] allow to unit test loop passes

The following arranges for the GIMPLE frontend to parse an
additional loops(...) specification, currently consisting of
'normal' and 'lcssa'.  The intent is to allow unit testing
of passes inside the GIMPLE loop optimization pipeline where
we keep the IL in loop-closed SSA and have SCEV initialized.

The GIMPLE parser side is only half of the story - the rest
of the patch makes sure we do not destroy loop state when
moving the IL through the skipped portion of the pass pipeline
which shows we are not careful with IPA passes here and those
tend to call loop_optimizer_init which destroys state.  The
patch arranges for IPA passes to honor fn->pass_startwith and
if set, refrain from considering the function.

Since the SCEV state is global we cannot initialize it during
GIMPLE parsing but we have to arrange for that to happen before
the pass we want to start with.  The patch heuristically
enables the loop-init pass based on the fact whether the IL
is in loop-closed SSA state and makes that aware of GIMPLE
testcases already arriving with properly initialized loops.

That's all quite some hacks but I think it's worth the ability
to unit test loop passes.

I've tried to do this before but PR104931 now triggered me to
try again (I have still to see whether that's enough to make   
a GIMPLE testcase trigger that bug).  I've skipped existing
GIMPLE testcases for -flto since when starting after IPA
using LTO doesn't make much sense and my IPA mangling ends up
crashing in the LTO writing.  There's possibly some better
way to "hide" the late to be started functions from IPA
(but we would still need to stream the body).

Bootstrapped and tested on x86_64-unknown-linux-gnu.

Any comments?

Thanks,
Richard.

2022-03-17  Richard Biener  <rguenther@suse.de>

gcc/c/
	* c-tree.h (c_declspecs::loops_state): Add.
	* c-parser.cc (c_parser_declaration_or_fndef): Pass down
	loops_state to c_parser_parse_gimple_body.
	* gimple-parser.h (c_parser_parse_gimple_body): Adjust.
	* gimple-parser.cc (c_parser_parse_gimple_body): Get
	and initialize loops state according to specification.
	(c_parser_gimple_or_rtl_pass_list): Parse loops[(spec...)]
	with supported spec 'normal' and 'lcssa'.

gcc/
	* passes.cc (should_skip_pass_p): When in LC SSA do not
	skip loopinit.
	* tree-ssa-loop.cc (pass_tree_loop_init::execute): Handle
	functions already in LC SSA.
	* ipa-cp.cc (ipcp_cloning_candidate_p): Skip functions
	with pending startwith pass.
	* ipa-fnsummary.c (ipa_fn_summary_generate): Likewise.
	* ipa-inline.cc (inline_small_functions): Likewise.
	(ipa_inline): Likewise.
	* ipa-modref.cc (modref_generate): Likewise.

gcc/testsuite/
	* gcc.dg/gimplefe-50.c: New testcase.
	* gcc.dg/torture/pr89595.c: Skip -flto.
	* gcc.dg/vect/bb-slp-48.c: Likewise.
	* gcc.dg/vect/slp-reduc-10a.c: Likewise.
	* gcc.dg/vect/slp-reduc-10b.c: Likewise.
	* gcc.dg/vect/slp-reduc-10c.c: Likewise.
	* gcc.dg/vect/slp-reduc-10d.c: Likewise.
	* gcc.dg/vect/slp-reduc-10e.c: Likewise.
	* gcc.dg/vect/vect-cond-arith-2.c: Likewise.
---
 gcc/c/c-parser.cc                             |  1 +
 gcc/c/c-tree.h                                |  3 ++
 gcc/c/gimple-parser.cc                        | 37 +++++++++++++-
 gcc/c/gimple-parser.h                         |  1 +
 gcc/ipa-cp.cc                                 |  4 +-
 gcc/ipa-fnsummary.cc                          |  4 +-
 gcc/ipa-inline.cc                             |  8 +++-
 gcc/ipa-modref.cc                             |  2 +-
 gcc/passes.cc                                 |  7 +++
 gcc/testsuite/gcc.dg/gimplefe-50.c            | 48 +++++++++++++++++++
 gcc/testsuite/gcc.dg/torture/pr89595.c        |  1 +
 gcc/testsuite/gcc.dg/vect/bb-slp-48.c         |  1 +
 gcc/testsuite/gcc.dg/vect/slp-reduc-10a.c     |  1 +
 gcc/testsuite/gcc.dg/vect/slp-reduc-10b.c     |  1 +
 gcc/testsuite/gcc.dg/vect/slp-reduc-10c.c     |  1 +
 gcc/testsuite/gcc.dg/vect/slp-reduc-10d.c     |  1 +
 gcc/testsuite/gcc.dg/vect/slp-reduc-10e.c     |  1 +
 gcc/testsuite/gcc.dg/vect/vect-cond-arith-2.c |  1 +
 gcc/tree-ssa-loop.cc                          | 11 +++--
 19 files changed, 125 insertions(+), 9 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/gimplefe-50.c

Richard Biener <rguenther@suse.de> writes:
> The following arranges for the GIMPLE frontend to parse an
> additional loops(...) specification, currently consisting of
> 'normal' and 'lcssa'.  The intent is to allow unit testing
> of passes inside the GIMPLE loop optimization pipeline where
> we keep the IL in loop-closed SSA and have SCEV initialized.
>
> The GIMPLE parser side is only half of the story - the rest
> of the patch makes sure we do not destroy loop state when
> moving the IL through the skipped portion of the pass pipeline
> which shows we are not careful with IPA passes here and those
> tend to call loop_optimizer_init which destroys state.  The
> patch arranges for IPA passes to honor fn->pass_startwith and
> if set, refrain from considering the function.
>
> Since the SCEV state is global we cannot initialize it during
> GIMPLE parsing but we have to arrange for that to happen before
> the pass we want to start with.  The patch heuristically
> enables the loop-init pass based on the fact whether the IL
> is in loop-closed SSA state and makes that aware of GIMPLE
> testcases already arriving with properly initialized loops.
>
> That's all quite some hacks but I think it's worth the ability
> to unit test loop passes.
>
> I've tried to do this before but PR104931 now triggered me to
> try again (I have still to see whether that's enough to make   
> a GIMPLE testcase trigger that bug).  I've skipped existing
> GIMPLE testcases for -flto since when starting after IPA
> using LTO doesn't make much sense and my IPA mangling ends up
> crashing in the LTO writing.  There's possibly some better
> way to "hide" the late to be started functions from IPA
> (but we would still need to stream the body).
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.

Don't think I'm really qualified to comment, but it seems OK to me FWIW.

Given that you've already found 4 places that need:

  (DECL_STRUCT_FUNCTION (node->decl)
   && DECL_STRUCT_FUNCTION (node->decl)->pass_startwith)

I guess it might be worth having a helper for it.

Thanks,
Richard

>
> Any comments?
>
> Thanks,
> Richard.
>
> 2022-03-17  Richard Biener  <rguenther@suse.de>
>
> gcc/c/
> 	* c-tree.h (c_declspecs::loops_state): Add.
> 	* c-parser.cc (c_parser_declaration_or_fndef): Pass down
> 	loops_state to c_parser_parse_gimple_body.
> 	* gimple-parser.h (c_parser_parse_gimple_body): Adjust.
> 	* gimple-parser.cc (c_parser_parse_gimple_body): Get
> 	and initialize loops state according to specification.
> 	(c_parser_gimple_or_rtl_pass_list): Parse loops[(spec...)]
> 	with supported spec 'normal' and 'lcssa'.
>
> gcc/
> 	* passes.cc (should_skip_pass_p): When in LC SSA do not
> 	skip loopinit.
> 	* tree-ssa-loop.cc (pass_tree_loop_init::execute): Handle
> 	functions already in LC SSA.
> 	* ipa-cp.cc (ipcp_cloning_candidate_p): Skip functions
> 	with pending startwith pass.
> 	* ipa-fnsummary.c (ipa_fn_summary_generate): Likewise.
> 	* ipa-inline.cc (inline_small_functions): Likewise.
> 	(ipa_inline): Likewise.
> 	* ipa-modref.cc (modref_generate): Likewise.
>
> gcc/testsuite/
> 	* gcc.dg/gimplefe-50.c: New testcase.
> 	* gcc.dg/torture/pr89595.c: Skip -flto.
> 	* gcc.dg/vect/bb-slp-48.c: Likewise.
> 	* gcc.dg/vect/slp-reduc-10a.c: Likewise.
> 	* gcc.dg/vect/slp-reduc-10b.c: Likewise.
> 	* gcc.dg/vect/slp-reduc-10c.c: Likewise.
> 	* gcc.dg/vect/slp-reduc-10d.c: Likewise.
> 	* gcc.dg/vect/slp-reduc-10e.c: Likewise.
> 	* gcc.dg/vect/vect-cond-arith-2.c: Likewise.
> ---
>  gcc/c/c-parser.cc                             |  1 +
>  gcc/c/c-tree.h                                |  3 ++
>  gcc/c/gimple-parser.cc                        | 37 +++++++++++++-
>  gcc/c/gimple-parser.h                         |  1 +
>  gcc/ipa-cp.cc                                 |  4 +-
>  gcc/ipa-fnsummary.cc                          |  4 +-
>  gcc/ipa-inline.cc                             |  8 +++-
>  gcc/ipa-modref.cc                             |  2 +-
>  gcc/passes.cc                                 |  7 +++
>  gcc/testsuite/gcc.dg/gimplefe-50.c            | 48 +++++++++++++++++++
>  gcc/testsuite/gcc.dg/torture/pr89595.c        |  1 +
>  gcc/testsuite/gcc.dg/vect/bb-slp-48.c         |  1 +
>  gcc/testsuite/gcc.dg/vect/slp-reduc-10a.c     |  1 +
>  gcc/testsuite/gcc.dg/vect/slp-reduc-10b.c     |  1 +
>  gcc/testsuite/gcc.dg/vect/slp-reduc-10c.c     |  1 +
>  gcc/testsuite/gcc.dg/vect/slp-reduc-10d.c     |  1 +
>  gcc/testsuite/gcc.dg/vect/slp-reduc-10e.c     |  1 +
>  gcc/testsuite/gcc.dg/vect/vect-cond-arith-2.c |  1 +
>  gcc/tree-ssa-loop.cc                          | 11 +++--
>  19 files changed, 125 insertions(+), 9 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/gimplefe-50.c
>
> diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
> index 129dd727ef3..80091d81bb4 100644
> --- a/gcc/c/c-parser.cc
> +++ b/gcc/c/c-parser.cc
> @@ -2537,6 +2537,7 @@ c_parser_declaration_or_fndef (c_parser *parser, bool fndef_ok,
>  	  in_late_binary_op = true;
>  	  c_parser_parse_gimple_body (parser, specs->gimple_or_rtl_pass,
>  				      specs->declspec_il,
> +				      specs->loops_state,
>  				      specs->entry_bb_count);
>  	  in_late_binary_op = saved;
>  	}
> diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
> index c70f0ba5ab6..b2a5b75b05f 100644
> --- a/gcc/c/c-tree.h
> +++ b/gcc/c/c-tree.h
> @@ -343,6 +343,9 @@ struct c_declspecs {
>    /* Any type specifier keyword used such as "int", not reflecting
>       modifiers such as "short", or cts_none if none.  */
>    ENUM_BITFIELD (c_typespec_keyword) typespec_word : 8;
> +  /* The loop specific IL state for __GIMPLE and __RTL, maps to
> +     the enum in cfgloop.h.  */
> +  unsigned loops_state : 8;
>    /* The kind of type specifier if one has been seen, ctsk_none
>       otherwise.  */
>    ENUM_BITFIELD (c_typespec_kind) typespec_kind : 4;
> diff --git a/gcc/c/gimple-parser.cc b/gcc/c/gimple-parser.cc
> index d1afd42556c..095684f549f 100644
> --- a/gcc/c/gimple-parser.cc
> +++ b/gcc/c/gimple-parser.cc
> @@ -211,6 +211,7 @@ c_parser_gimple_parse_bb_spec_edge_probability (tree val,
>  void
>  c_parser_parse_gimple_body (c_parser *cparser, char *gimple_pass,
>  			    enum c_declspec_il cdil,
> +			    unsigned loops_state,
>  			    profile_count entry_bb_count)
>  {
>    gimple_parser parser (cparser);
> @@ -240,7 +241,11 @@ c_parser_parse_gimple_body (c_parser *cparser, char *gimple_pass,
>           mark headers and leave the rest to fixup.  */
>        set_loops_for_fn (cfun, ggc_cleared_alloc<struct loops> ());
>        init_loops_structure (cfun, loops_for_fn (cfun), 1);
> -      loops_state_set (cfun, LOOPS_NEED_FIXUP|LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
> +      if (loops_state == 0)
> +	loops_state_set (cfun,
> +			 LOOPS_NEED_FIXUP|LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
> +      else
> +	loops_state_set (cfun, LOOPS_NEED_FIXUP|loops_state);
>        cfun->curr_properties
>  	|= PROP_gimple_lcf | PROP_gimple_leh | PROP_cfg | PROP_loops;
>        if (cdil == cdil_gimple_ssa)
> @@ -1975,6 +1980,36 @@ c_parser_gimple_or_rtl_pass_list (c_parser *parser, c_declspecs *specs)
>  	  if (!c_parser_require (parser, CPP_CLOSE_PAREN, "expected %<)%>"))
>  	    return;
>  	}
> +      else if (! strcmp (op, "loops"))
> +	{
> +	  if (c_parser_next_token_is (parser, CPP_OPEN_PAREN))
> +	    {
> +	      c_parser_consume_token (parser);
> +	      while (c_parser_next_token_is (parser, CPP_NAME))
> +		{
> +		  const char *lop
> +		    = IDENTIFIER_POINTER (c_parser_peek_token (parser)->value);
> +		  c_parser_consume_token (parser);
> +		  if (! strcmp (lop, "normal"))
> +		    specs->loops_state |= LOOPS_NORMAL;
> +		  else if (! strcmp (lop, "lcssa"))
> +		    specs->loops_state |= LOOP_CLOSED_SSA;
> +		  else
> +		    {
> +		      error_at (c_parser_peek_token (parser)->location,
> +				"invalid loop state");
> +		      return;
> +		    }
> +		  if (c_parser_next_token_is (parser, CPP_COMMA))
> +		    c_parser_consume_token (parser);
> +		}
> +	      if (!c_parser_require (parser, CPP_CLOSE_PAREN, "expected %<)%>"))
> +		return;
> +	    }
> +	  else
> +	    /* LOOPS_NORMAL */
> +	    specs->loops_state = LOOPS_NORMAL;
> +	}
>        else if (specs->declspec_il != cdil_gimple)
>  	/* Allow only one IL specifier and none on RTL.  */
>  	;
> diff --git a/gcc/c/gimple-parser.h b/gcc/c/gimple-parser.h
> index 2881a657640..6aed6010343 100644
> --- a/gcc/c/gimple-parser.h
> +++ b/gcc/c/gimple-parser.h
> @@ -23,6 +23,7 @@ along with GCC; see the file COPYING3.  If not see
>  /* Gimple parsing functions.  */
>  extern void c_parser_parse_gimple_body (c_parser *, char *,
>  					enum c_declspec_il,
> +					unsigned loops_state,
>  					profile_count);
>  extern void c_parser_gimple_or_rtl_pass_list (c_parser *, c_declspecs *);
>  
> diff --git a/gcc/ipa-cp.cc b/gcc/ipa-cp.cc
> index 18047c209a8..348ba878331 100644
> --- a/gcc/ipa-cp.cc
> +++ b/gcc/ipa-cp.cc
> @@ -777,7 +777,9 @@ ipcp_cloning_candidate_p (struct cgraph_node *node)
>  
>    gcc_checking_assert (node->has_gimple_body_p ());
>  
> -  if (!opt_for_fn (node->decl, flag_ipa_cp_clone))
> +  if (!opt_for_fn (node->decl, flag_ipa_cp_clone)
> +      || (DECL_STRUCT_FUNCTION (node->decl)
> +	  && DECL_STRUCT_FUNCTION (node->decl)->pass_startwith))
>      {
>        if (dump_file)
>  	fprintf (dump_file, "Not considering %s for cloning; "
> diff --git a/gcc/ipa-fnsummary.cc b/gcc/ipa-fnsummary.cc
> index 0d7e395c846..10b679bbb27 100644
> --- a/gcc/ipa-fnsummary.cc
> +++ b/gcc/ipa-fnsummary.cc
> @@ -4354,7 +4354,9 @@ ipa_fn_summary_generate (void)
>    FOR_EACH_DEFINED_FUNCTION (node)
>      if (!node->alias
>  	&& (flag_generate_lto || flag_generate_offload|| flag_wpa
> -	    || opt_for_fn (node->decl, optimize)))
> +	    || opt_for_fn (node->decl, optimize))
> +	&& !(DECL_STRUCT_FUNCTION (node->decl)
> +	     && DECL_STRUCT_FUNCTION (node->decl)->pass_startwith))
>        inline_analyze_function (node);
>  }
>  
> diff --git a/gcc/ipa-inline.cc b/gcc/ipa-inline.cc
> index f8bb072c422..8352e9f0dce 100644
> --- a/gcc/ipa-inline.cc
> +++ b/gcc/ipa-inline.cc
> @@ -1974,7 +1974,9 @@ inline_small_functions (void)
>        {
>  	if (!node->alias && node->analyzed
>  	    && (node->has_gimple_body_p () || node->thunk)
> -	    && opt_for_fn (node->decl, optimize))
> +	    && opt_for_fn (node->decl, optimize)
> +	    && !(DECL_STRUCT_FUNCTION (node->decl)
> +		 && DECL_STRUCT_FUNCTION (node->decl)->pass_startwith))
>  	  {
>  	    class ipa_fn_summary *info = ipa_fn_summaries->get (node);
>  	    struct ipa_dfs_info *dfs = (struct ipa_dfs_info *) node->aux;
> @@ -2792,7 +2794,9 @@ ipa_inline (void)
>  	  bool update=false;
>  
>  	  if (!opt_for_fn (node->decl, optimize)
> -	      || !opt_for_fn (node->decl, flag_inline_functions_called_once))
> +	      || !opt_for_fn (node->decl, flag_inline_functions_called_once)
> +	      || (DECL_STRUCT_FUNCTION (node->decl)
> +		  && DECL_STRUCT_FUNCTION (node->decl)->pass_startwith))
>  	    continue;
>  
>  	  for (edge = node->callees; edge; edge = next)
> diff --git a/gcc/ipa-modref.cc b/gcc/ipa-modref.cc
> index acfd7d80ff8..0f9c98bcc03 100644
> --- a/gcc/ipa-modref.cc
> +++ b/gcc/ipa-modref.cc
> @@ -3370,7 +3370,7 @@ modref_generate (void)
>    FOR_EACH_FUNCTION_WITH_GIMPLE_BODY (node)
>      {
>        function *f = DECL_STRUCT_FUNCTION (node->decl);
> -      if (!f)
> +      if (!f || f->pass_startwith)
>  	continue;
>        push_cfun (f);
>        analyze_function (true);
> diff --git a/gcc/passes.cc b/gcc/passes.cc
> index 00f856e0754..4dbc405cfd4 100644
> --- a/gcc/passes.cc
> +++ b/gcc/passes.cc
> @@ -2510,6 +2510,13 @@ should_skip_pass_p (opt_pass *pass)
>    if (strstr (pass->name, "build_cgraph_edges") != NULL)
>      return false;
>  
> +  /* When the function is in LCSSA arrange for SCEV to be initialized
> +     via pass_tree_loop_init.  */
> +  if (loops_for_fn (cfun)
> +      && loops_state_satisfies_p (cfun, LOOP_CLOSED_SSA)
> +      && strstr (pass->name, "loopinit") != NULL)
> +    return false;
> +
>    /* Don't skip df init; later RTL passes need it.  */
>    if (strstr (pass->name, "dfinit") != NULL
>        || strstr (pass->name, "dfinish") != NULL)
> diff --git a/gcc/testsuite/gcc.dg/gimplefe-50.c b/gcc/testsuite/gcc.dg/gimplefe-50.c
> new file mode 100644
> index 00000000000..3565615e80b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/gimplefe-50.c
> @@ -0,0 +1,48 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -fgimple" } */
> +
> +void __GIMPLE (ssa,startwith("ivcanon"),loops(normal,lcssa))
> +foo (int n, double * x)
> +{
> +  int i;
> +  __SIZETYPE__ _1;
> +  __SIZETYPE__ _2;
> +  double * _3;
> +  double _4;
> +
> +  __BB(2):
> +  if (n_8(D) > 0)
> +    goto __BB5;
> +  else
> +    goto __BB4;
> +
> +  __BB(5):
> +  goto __BB3;
> +
> +  __BB(3,loop_header(1)):
> +  i_14 = __PHI (__BB6: i_11, __BB5: 0);
> +  _1 = (__SIZETYPE__) i_14;
> +  _2 = _1 * _Literal (__SIZETYPE__) 8u;
> +  _3 = x_9(D) + _2;
> +  _4 = (double) i_14;
> +  __MEM <double> (_3) = _4;
> +  i_11 = i_14 + 1;
> +  if (n_8(D) > i_11)
> +    goto __BB6;
> +  else
> +    goto __BB4;
> +
> +  __BB(6):
> +  goto __BB3;
> +
> +  __BB(4):
> +  return;
> +
> +}
> +
> +int main()
> +{
> +  double x[1024];
> +  foo (1024, x);
> +  return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/torture/pr89595.c b/gcc/testsuite/gcc.dg/torture/pr89595.c
> index f45dc98c3f0..65c375f69cb 100644
> --- a/gcc/testsuite/gcc.dg/torture/pr89595.c
> +++ b/gcc/testsuite/gcc.dg/torture/pr89595.c
> @@ -1,4 +1,5 @@
>  /* { dg-do run } */
> +/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
>  /* { dg-additional-options "-fgimple" } */
>  
>  int __attribute__((noipa))
> diff --git a/gcc/testsuite/gcc.dg/vect/bb-slp-48.c b/gcc/testsuite/gcc.dg/vect/bb-slp-48.c
> index dfae6177b21..b54bc580920 100644
> --- a/gcc/testsuite/gcc.dg/vect/bb-slp-48.c
> +++ b/gcc/testsuite/gcc.dg/vect/bb-slp-48.c
> @@ -1,4 +1,5 @@
>  /* { dg-do compile } */
> +/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
>  /* { dg-additional-options "-fgimple -fdump-tree-optimized" } */
>  /* { dg-require-effective-target vect_double } */
>  
> diff --git a/gcc/testsuite/gcc.dg/vect/slp-reduc-10a.c b/gcc/testsuite/gcc.dg/vect/slp-reduc-10a.c
> index d3c2c2d7f54..790e1e7eb14 100644
> --- a/gcc/testsuite/gcc.dg/vect/slp-reduc-10a.c
> +++ b/gcc/testsuite/gcc.dg/vect/slp-reduc-10a.c
> @@ -1,4 +1,5 @@
>  /* { dg-do compile } */
> +/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
>  /* { dg-require-effective-target vect_int } */
>  /* { dg-additional-options "-fgimple" } */
>  
> diff --git a/gcc/testsuite/gcc.dg/vect/slp-reduc-10b.c b/gcc/testsuite/gcc.dg/vect/slp-reduc-10b.c
> index 6a0d55def30..25c261dfa82 100644
> --- a/gcc/testsuite/gcc.dg/vect/slp-reduc-10b.c
> +++ b/gcc/testsuite/gcc.dg/vect/slp-reduc-10b.c
> @@ -1,4 +1,5 @@
>  /* { dg-do compile } */
> +/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
>  /* { dg-require-effective-target vect_int } */
>  /* { dg-additional-options "-fgimple" } */
>  
> diff --git a/gcc/testsuite/gcc.dg/vect/slp-reduc-10c.c b/gcc/testsuite/gcc.dg/vect/slp-reduc-10c.c
> index 20df2626764..f3502fd3e18 100644
> --- a/gcc/testsuite/gcc.dg/vect/slp-reduc-10c.c
> +++ b/gcc/testsuite/gcc.dg/vect/slp-reduc-10c.c
> @@ -1,4 +1,5 @@
>  /* { dg-do compile } */
> +/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
>  /* { dg-require-effective-target vect_int } */
>  /* { dg-additional-options "-fgimple" } */
>  
> diff --git a/gcc/testsuite/gcc.dg/vect/slp-reduc-10d.c b/gcc/testsuite/gcc.dg/vect/slp-reduc-10d.c
> index 8a512d5c14d..77cf2fc4d9e 100644
> --- a/gcc/testsuite/gcc.dg/vect/slp-reduc-10d.c
> +++ b/gcc/testsuite/gcc.dg/vect/slp-reduc-10d.c
> @@ -1,4 +1,5 @@
>  /* { dg-do compile } */
> +/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
>  /* { dg-require-effective-target vect_int } */
>  /* { dg-additional-options "-fgimple" } */
>  
> diff --git a/gcc/testsuite/gcc.dg/vect/slp-reduc-10e.c b/gcc/testsuite/gcc.dg/vect/slp-reduc-10e.c
> index 268ec9db77d..879d34708b4 100644
> --- a/gcc/testsuite/gcc.dg/vect/slp-reduc-10e.c
> +++ b/gcc/testsuite/gcc.dg/vect/slp-reduc-10e.c
> @@ -1,4 +1,5 @@
>  /* { dg-do compile } */
> +/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
>  /* { dg-require-effective-target vect_int } */
>  /* { dg-additional-options "-fgimple" } */
>  
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-cond-arith-2.c b/gcc/testsuite/gcc.dg/vect/vect-cond-arith-2.c
> index 38994ea82a5..49d3a17108a 100644
> --- a/gcc/testsuite/gcc.dg/vect/vect-cond-arith-2.c
> +++ b/gcc/testsuite/gcc.dg/vect/vect-cond-arith-2.c
> @@ -1,4 +1,5 @@
>  /* { dg-do compile } */
> +/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
>  /* { dg-additional-options "-fgimple -fdump-tree-optimized -ffast-math" } */
>  
>  double __GIMPLE (ssa, startwith("loop"))
> diff --git a/gcc/tree-ssa-loop.cc b/gcc/tree-ssa-loop.cc
> index 73aa46627b4..21878342aed 100644
> --- a/gcc/tree-ssa-loop.cc
> +++ b/gcc/tree-ssa-loop.cc
> @@ -354,9 +354,14 @@ pass_tree_loop_init::execute (function *fun ATTRIBUTE_UNUSED)
>  					      | LOOP_CLOSED_SSA)
>  	&& scev_initialized_p ())
>    */
> -  loop_optimizer_init (LOOPS_NORMAL
> -		       | LOOPS_HAVE_RECORDED_EXITS);
> -  rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa);
> +  /* When a __GIMPLE testcase starts with a pass inside the loop pipeline
> +     we already are in loop-closed SSA but still need to initialize SCEV.  */
> +  if (!loops_state_satisfies_p (fun, LOOP_CLOSED_SSA))
> +    {
> +      loop_optimizer_init (LOOPS_NORMAL
> +			   | LOOPS_HAVE_RECORDED_EXITS);
> +      rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa);
> +    }
>    scev_initialize ();
>  
>    return 0;