Re: RFC [1/2] divmod transform

[Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>]

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On 24 May 2016 at 17:42, Richard Biener <rguenther@suse.de> wrote:
> On Tue, 24 May 2016, Prathamesh Kulkarni wrote:
>
>> On 23 May 2016 at 17:35, Richard Biener <richard.guenther@gmail.com> wrote:
>> > On Mon, May 23, 2016 at 10:58 AM, Prathamesh Kulkarni
>> > <prathamesh.kulkarni@linaro.org> wrote:
>> >> Hi,
>> >> I have updated my patch for divmod (attached), which was originally
>> >> based on Kugan's patch.
>> >> The patch transforms stmts with code TRUNC_DIV_EXPR and TRUNC_MOD_EXPR
>> >> having same operands to divmod representation, so we can cse computation of mod.
>> >>
>> >> t1 = a TRUNC_DIV_EXPR b;
>> >> t2 = a TRUNC_MOD_EXPR b
>> >> is transformed to:
>> >> complex_tmp = DIVMOD (a, b);
>> >> t1 = REALPART_EXPR (complex_tmp);
>> >> t2 = IMAGPART_EXPR (complex_tmp);
>> >>
>> >> * New hook divmod_expand_libfunc
>> >> The rationale for introducing the hook is that different targets have
>> >> incompatible calling conventions for divmod libfunc.
>> >> Currently three ports define divmod libfunc: c6x, spu and arm.
>> >> c6x and spu follow the convention of libgcc2.c:__udivmoddi4:
>> >> return quotient and store remainder in argument passed as pointer,
>> >> while the arm version takes two arguments and returns both
>> >> quotient and remainder having mode double the size of the operand mode.
>> >> The port should hence override the hook expand_divmod_libfunc
>> >> to generate call to target-specific divmod.
>> >> Ports should define this hook if:
>> >> a) The port does not have divmod or div insn for the given mode.
>> >> b) The port defines divmod libfunc for the given mode.
>> >> The default hook default_expand_divmod_libfunc() generates call
>> >> to libgcc2.c:__udivmoddi4 provided the operands are unsigned and
>> >> are of DImode.
>> >>
>> >> Patch passes bootstrap+test on x86_64-unknown-linux-gnu and
>> >> cross-tested on arm*-*-*.
>> >> Bootstrap+test in progress on arm-linux-gnueabihf.
>> >> Does this patch look OK ?
>> >
>> > diff --git a/gcc/targhooks.c b/gcc/targhooks.c
>> > index 6b4601b..e4a021a 100644
>> > --- a/gcc/targhooks.c
>> > +++ b/gcc/targhooks.c
>> > @@ -1965,4 +1965,31 @@ default_optab_supported_p (int, machine_mode,
>> > machine_mode, optimization_type)
>> >    return true;
>> >  }
>> >
>> > +void
>> > +default_expand_divmod_libfunc (bool unsignedp, machine_mode mode,
>> > +                              rtx op0, rtx op1,
>> > +                              rtx *quot_p, rtx *rem_p)
>> >
>> > functions need a comment.
>> >
>> > ISTR it was suggested that ARM change to libgcc2.c__udivmoddi4 style?  In that
>> > case we could avoid the target hook.
>> Well I would prefer adding the hook because that's more easier -;)
>> Would it be ok for now to go with the hook ?
>> >
>> > +      /* If target overrides expand_divmod_libfunc hook
>> > +        then perform divmod by generating call to the target-specifc divmod
>> > libfunc.  */
>> > +      if (targetm.expand_divmod_libfunc != default_expand_divmod_libfunc)
>> > +       return true;
>> > +
>> > +      /* Fall back to using libgcc2.c:__udivmoddi4.  */
>> > +      return (mode == DImode && unsignedp);
>> >
>> > I don't understand this - we know optab_libfunc returns non-NULL for 'mode'
>> > but still restrict this to DImode && unsigned?  Also if
>> > targetm.expand_divmod_libfunc
>> > is not the default we expect the target to handle all modes?
>> Ah indeed, the check for DImode is unnecessary.
>> However I suppose the check for unsignedp should be there,
>> since we want to generate call to __udivmoddi4 only if operand is unsigned ?
>
> The optab libfunc for sdivmod should be NULL in that case.
Ah indeed, thanks.
>
>> >
>> > That said - I expected the above piece to be simply a 'return true;' ;)
>> >
>> > Usually we use some can_expand_XXX helper in optabs.c to query if the target
>> > supports a specific operation (for example SImode divmod would use DImode
>> > divmod by means of widening operands - for the unsigned case of course).
>> Thanks for pointing out. So if a target does not support divmod
>> libfunc for a mode
>> but for a wider mode, then we could zero-extend operands to the wider-mode,
>> perform divmod on the wider-mode, and then cast result back to the
>> original mode.
>> I haven't done that in this patch, would it be OK to do that as a follow up ?
>
> I think that you should conservatively handle the div_optab query, thus if
> the target has a HW division in a wider mode don't use the divmod IFN.
> You'd simply iterate over GET_MODE_WIDER_MODE and repeat the
> if (optab_handler (div_optab, mode) != CODE_FOR_nothing) check, bailing
> out if that is available.
Done.
>
>> > +  /* Disable the transform if either is a constant, since
>> > division-by-constant
>> > +     may have specialized expansion.  */
>> > +  if (TREE_CONSTANT (op1) || TREE_CONSTANT (op2))
>> > +    return false;
>> >
>> > please use CONSTANT_CLASS_P (op1) || CONSTANT_CLASS_P (op2)
>> >
>> > +  if (TYPE_OVERFLOW_TRAPS (type))
>> > +    return false;
>> >
>> > why's that?  Generally please first test cheap things (trapping, constant-ness)
>> > before checking expensive stuff (target_supports_divmod_p).
>> I added TYPE_OVERFLOW_TRAPS (type) based on your suggestion in:
>> https://www.mail-archive.com/gcc@gcc.gnu.org/msg78534.html
>> "When looking at TRUNC_DIV_EXPR you should also exclude
>> the case where TYPE_OVERFLOW_TRAPS (type) as that should
>> expand using the [su]divv optabs (no trapping overflow
>> divmod optab exists)."
>
> Ok, didn't remember that.
>
>> >
>> > +static bool
>> > +convert_to_divmod (gassign *stmt)
>> > +{
>> > +  if (!divmod_candidate_p (stmt))
>> > +    return false;
>> > +
>> > +  tree op1 = gimple_assign_rhs1 (stmt);
>> > +  tree op2 = gimple_assign_rhs2 (stmt);
>> > +
>> > +  vec<gimple *> stmts = vNULL;
>> >
>> > use an auto_vec <gimple *> - you currently leak it in at least one place.
>> >
>> > +      if (maybe_clean_or_replace_eh_stmt (use_stmt, use_stmt))
>> > +       cfg_changed = true;
>> >
>> > note that this suggests you should check whether any of the stmts may throw
>> > internally as you don't update / transfer EH info correctly.  So for 'stmt' and
>> > all 'use_stmt' check stmt_can_throw_internal and if so do not add it to
>> > the list of stmts to modify.
>> >
>> > Btw, I think you should not add 'stmt' immediately but when iterating over
>> > all uses also gather uses in TRUNC_MOD_EXPR.
>> >
>> > Otherwise looks ok.
>> Done changes in this version. I am gathering mod uses same time as div uses,
>> so this imposes a constraint that mod dominates mod. I am not sure if
>> that's desirable.
>
> I think you also need a mod_seen variable now that you don't necessarily
> end up with 'stmt' in the vector of stmts.  I don't see how there is a
> constraint that mod dominates mod - it's just that the top_stmt needs
> to dominate all other uses that can be replaced with replacing top_stmt
> with a divmod.  It's just that the actual stmt set we choose may now
> depend on immediate uses order which on a second thought is bad
> as immediate uses order could be affected by debug stmts ... hmm.
>
> To avoid this please re-add the code adding 'stmt' to stmts immediately
> and add a use_stmt != stmt check to the immediate use processing loop
> so that we don't end up adding it twice.
Well I wonder what will happen for the following case:
t1 = x / y;
if (cond)
  t2 = x % y;
else
  t3 = x % y;

Assuming stmt == top_stmt is "t2 = x % y" and use_stmt is "t3 = x % y",
use_stmt will not get added to stmts vector, since top_stmt and
use_stmt are not in same bb,
and bb's containing top_stmt and use_stmt don't dominate each other.
Not sure if this is practical case (I assume fre will hoist mod
outside if-else?)

Now that we immediately add stmt to stmts vector, I suppose mod_seen
shall not be required ?

Thanks,
Prathamesh
>
> Richard.

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diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 8c7f2a1..111f19f 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -6963,6 +6963,12 @@ This is firstly introduced on ARM/AArch64 targets, please refer to
 the hook implementation for how different fusion types are supported.
 @end deftypefn
 
+@deftypefn {Target Hook} void TARGET_EXPAND_DIVMOD_LIBFUNC (bool @var{unsignedp}, machine_mode @var{mode}, @var{rtx}, @var{rtx}, rtx *@var{quot}, rtx *@var{rem})
+Define this hook if the port does not have hardware div and divmod insn for
+the given mode but has divmod libfunc, which is incompatible
+with libgcc2.c:__udivmoddi4
+@end deftypefn
+
 @node Sections
 @section Dividing the Output into Sections (Texts, Data, @dots{})
 @c the above section title is WAY too long.  maybe cut the part between
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index f963a58..2c9a800 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -4848,6 +4848,8 @@ them: try the first ones in this list first.
 
 @hook TARGET_SCHED_FUSION_PRIORITY
 
+@hook TARGET_EXPAND_DIVMOD_LIBFUNC
+
 @node Sections
 @section Dividing the Output into Sections (Texts, Data, @dots{})
 @c the above section title is WAY too long.  maybe cut the part between
diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
index c867ddc..0cb59f7 100644
--- a/gcc/internal-fn.c
+++ b/gcc/internal-fn.c
@@ -2276,6 +2276,48 @@ multi_vector_optab_supported_p (convert_optab optab, tree_pair types,
 #define direct_mask_store_optab_supported_p direct_optab_supported_p
 #define direct_store_lanes_optab_supported_p multi_vector_optab_supported_p
 
+/* Expand DIVMOD() using:
+ a) optab handler for udivmod/sdivmod if it is available.
+ b) If optab_handler doesn't exist, Generate call to
+    optab_libfunc for udivmod/sdivmod.  */
+
+static void 
+expand_DIVMOD (internal_fn, gcall *stmt)
+{
+  tree lhs = gimple_call_lhs (stmt);
+  tree arg0 = gimple_call_arg (stmt, 0);
+  tree arg1 = gimple_call_arg (stmt, 1);
+
+  gcc_assert (TREE_CODE (TREE_TYPE (lhs)) == COMPLEX_TYPE);
+  tree type = TREE_TYPE (TREE_TYPE (lhs));
+  machine_mode mode = TYPE_MODE (type);
+  bool unsignedp = TYPE_UNSIGNED (type);
+  optab tab = (unsignedp) ? udivmod_optab : sdivmod_optab;
+
+  rtx op0 = expand_normal (arg0);
+  rtx op1 = expand_normal (arg1);
+  rtx target = expand_expr (lhs, NULL_RTX, VOIDmode, EXPAND_WRITE);
+
+  rtx quotient, remainder;
+
+  /* Check if optab handler exists for [u]divmod.  */
+  if (optab_handler (tab, mode) != CODE_FOR_nothing)
+    {
+      quotient = gen_reg_rtx (mode);
+      remainder = gen_reg_rtx (mode);
+      expand_twoval_binop (tab, op0, op1, quotient, remainder, unsignedp);
+    }
+  else
+    targetm.expand_divmod_libfunc (unsignedp, mode, op0, op1,
+				   &quotient, &remainder);
+
+  /* Wrap the return value (quotient, remainder) within COMPLEX_EXPR.  */
+  expand_expr (build2 (COMPLEX_EXPR, TREE_TYPE (lhs),
+		       make_tree (TREE_TYPE (arg0), quotient),
+		       make_tree (TREE_TYPE (arg1), remainder)),
+	       target, VOIDmode, EXPAND_NORMAL);
+}
+
 /* Return true if FN is supported for the types in TYPES when the
    optimization type is OPT_TYPE.  The types are those associated with
    the "type0" and "type1" fields of FN's direct_internal_fn_info
diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def
index e729d85..56a80f1 100644
--- a/gcc/internal-fn.def
+++ b/gcc/internal-fn.def
@@ -194,6 +194,9 @@ DEF_INTERNAL_FN (ATOMIC_BIT_TEST_AND_SET, ECF_LEAF | ECF_NOTHROW, NULL)
 DEF_INTERNAL_FN (ATOMIC_BIT_TEST_AND_COMPLEMENT, ECF_LEAF | ECF_NOTHROW, NULL)
 DEF_INTERNAL_FN (ATOMIC_BIT_TEST_AND_RESET, ECF_LEAF | ECF_NOTHROW, NULL)
 
+/* Divmod function.  */
+DEF_INTERNAL_FN (DIVMOD, ECF_CONST | ECF_LEAF, NULL)
+
 #undef DEF_INTERNAL_INT_FN
 #undef DEF_INTERNAL_FLT_FN
 #undef DEF_INTERNAL_OPTAB_FN
diff --git a/gcc/target.def b/gcc/target.def
index 6392e73..4496f9a 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -4948,6 +4948,16 @@ Normally, this is not needed.",
  bool, (const_tree field, machine_mode mode),
  default_member_type_forces_blk)
 
+/* See tree-ssa-math-opts.c:divmod_candidate_p for conditions that gate
+   the divmod transform.  */
+DEFHOOK
+(expand_divmod_libfunc,
+ "Define this hook if the port does not have hardware div and divmod insn for\n\
+the given mode but has divmod libfunc, which is incompatible\n\
+with libgcc2.c:__udivmoddi4",
+ void, (bool unsignedp, machine_mode mode, rtx, rtx, rtx *quot, rtx *rem),
+ default_expand_divmod_libfunc)
+
 /* Return the class for a secondary reload, and fill in extra information.  */
 DEFHOOK
 (secondary_reload,
diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index 6b4601b..20327a6 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -1965,4 +1965,31 @@ default_optab_supported_p (int, machine_mode, machine_mode, optimization_type)
   return true;
 }
 
+/* Generate call to
+   DImode __udivmoddi4 (DImode op0, DImode op1, DImode *rem).  */
+
+void
+default_expand_divmod_libfunc (bool unsignedp, machine_mode mode,
+			       rtx op0, rtx op1,
+			       rtx *quot_p, rtx *rem_p)
+{
+  gcc_assert (mode == DImode);
+  gcc_assert (unsignedp);
+
+  rtx libfunc = optab_libfunc (udivmod_optab, DImode);
+  gcc_assert (libfunc);
+
+  rtx remainder = assign_stack_temp (DImode, GET_MODE_SIZE (DImode));
+  rtx address = XEXP (remainder, 0);
+
+  rtx quotient = emit_library_call_value (libfunc, NULL_RTX, LCT_CONST,
+					  DImode, 3,
+					  op0, GET_MODE (op0),
+					  op1, GET_MODE (op1),
+					  address, GET_MODE (address));
+
+  *quot_p = quotient;
+  *rem_p = remainder;
+}
+
 #include "gt-targhooks.h"
diff --git a/gcc/targhooks.h b/gcc/targhooks.h
index 7687c39..dc5e8e7 100644
--- a/gcc/targhooks.h
+++ b/gcc/targhooks.h
@@ -254,4 +254,7 @@ extern void default_setup_incoming_vararg_bounds (cumulative_args_t ca ATTRIBUTE
 extern bool default_optab_supported_p (int, machine_mode, machine_mode,
 				       optimization_type);
 
+extern void default_expand_divmod_libfunc (bool, machine_mode,
+					   rtx, rtx, rtx *, rtx *);
+
 #endif /* GCC_TARGHOOKS_H */
diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
index 81688cd..242b676 100644
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -112,6 +112,9 @@ along with GCC; see the file COPYING3.  If not see
 #include "params.h"
 #include "internal-fn.h"
 #include "case-cfn-macros.h"
+#include "optabs-libfuncs.h"
+#include "tree-eh.h"
+#include "targhooks.h"
 
 /* This structure represents one basic block that either computes a
    division, or is a common dominator for basic block that compute a
@@ -184,6 +187,9 @@ static struct
 
   /* Number of fp fused multiply-add ops inserted.  */
   int fmas_inserted;
+
+  /* Number of divmod calls inserted.  */
+  int divmod_calls_inserted;
 } widen_mul_stats;
 
 /* The instance of "struct occurrence" representing the highest
@@ -3784,6 +3790,196 @@ match_uaddsub_overflow (gimple_stmt_iterator *gsi, gimple *stmt,
   return true;
 }
 
+/* Return true if target has support for divmod.  */
+
+static bool
+target_supports_divmod_p (optab divmod_optab, optab div_optab, machine_mode mode)
+{
+  /* If target supports hardware divmod insn, use it for divmod.  */
+  if (optab_handler (divmod_optab, mode) != CODE_FOR_nothing)
+    return true;
+
+  /* Check if libfunc for divmod is available.  */
+  if (optab_libfunc (divmod_optab, mode) != NULL_RTX)
+    {
+      /* If optab_handler exists for div_optab, perhaps in a wider mode,
+	 we don't want to use the libfunc even if it exists for given mode.  */ 
+      for (machine_mode div_mode = mode;
+	   div_mode != VOIDmode;
+	   div_mode = GET_MODE_WIDER_MODE (div_mode))
+	if (optab_handler (div_optab, div_mode) != CODE_FOR_nothing)
+	  return false;
+ 
+      return true;
+    }
+
+  return false;
+}
+
+/* Check if stmt is candidate for divmod transform.  */
+
+static bool
+divmod_candidate_p (gassign *stmt)
+{
+  tree type = TREE_TYPE (gimple_assign_lhs (stmt));
+  enum machine_mode mode = TYPE_MODE (type);
+  optab divmod_optab, div_optab;
+
+  if (TYPE_UNSIGNED (type))
+    {
+      divmod_optab = udivmod_optab;
+      div_optab = udiv_optab;
+    }
+  else
+    {
+      divmod_optab = sdivmod_optab;
+      div_optab = sdiv_optab;
+    }
+
+  tree op1 = gimple_assign_rhs1 (stmt);
+  tree op2 = gimple_assign_rhs2 (stmt);
+
+  /* Disable the transform if either is a constant, since division-by-constant
+     may have specialized expansion.  */
+  if (CONSTANT_CLASS_P (op1) || CONSTANT_CLASS_P (op2))
+    return false;
+
+  /* Exclude the case where TYPE_OVERFLOW_TRAPS (type) as that should
+     expand using the [su]divv optabs.  */
+  if (TYPE_OVERFLOW_TRAPS (type))
+    return false;
+  
+  if (!target_supports_divmod_p (divmod_optab, div_optab, mode))
+    return false;
+
+  return true;
+}
+
+/* This function looks for:
+   t1 = a TRUNC_DIV_EXPR b;
+   t2 = a TRUNC_MOD_EXPR b;
+   and transforms it to the following sequence:
+   complex_tmp = DIVMOD (a, b);
+   t1 = REALPART_EXPR(a);
+   t2 = IMAGPART_EXPR(b);
+   For conditions enabling the transform see divmod_candidate_p().
+
+   The pass works in two phases:
+   1) Walk through all immediate uses of stmt's operand and find a
+      TRUNC_DIV_EXPR with matching operands and if such a stmt is found add
+      it to stmts vector.
+   2) Insert DIVMOD call before first div/mod stmt in top_bb (basic block that
+      dominates other div/mod stmts with same operands) and update entries in
+      stmts vector to use return value of DIMOVD (REALEXPR_PART for div,
+      IMAGPART_EXPR for mod).  */
+
+static bool
+convert_to_divmod (gassign *stmt)
+{
+  if (!divmod_candidate_p (stmt))
+    return false;
+
+  tree op1 = gimple_assign_rhs1 (stmt);
+  tree op2 = gimple_assign_rhs2 (stmt);
+  gimple *top_stmt = stmt;
+  basic_block top_bb = gimple_bb (top_stmt); 
+  bool div_seen = false;
+  imm_use_iterator use_iter;
+  gimple *use_stmt;
+  auto_vec<gimple *> stmts; 
+  
+  stmts.safe_push (stmt);  
+  FOR_EACH_IMM_USE_STMT (use_stmt, use_iter, op1)
+    {
+      /* Check if use_stmt is TRUNC_DIV_EXPR with same operands as stmt.  */
+      if (is_gimple_assign (use_stmt)
+	  && (gimple_assign_rhs_code (use_stmt) == TRUNC_DIV_EXPR
+	      || gimple_assign_rhs_code (use_stmt) == TRUNC_MOD_EXPR)
+	  && operand_equal_p (op1, gimple_assign_rhs1 (use_stmt), 0)
+	  && operand_equal_p (op2, gimple_assign_rhs2 (use_stmt), 0))
+	{
+	  if (stmt_can_throw_internal (use_stmt))
+	    continue;
+
+	  if (use_stmt == stmt)
+	    continue;
+
+	  basic_block bb = gimple_bb (use_stmt);
+	  top_bb = gimple_bb (top_stmt);
+
+	  if (top_bb == bb)
+	    {
+	      stmts.safe_push (use_stmt);
+	      if (gimple_uid (use_stmt) < gimple_uid (top_stmt))
+		top_stmt = use_stmt;
+	    }
+	  else if (dominated_by_p (CDI_DOMINATORS, top_bb, bb))
+	    {
+	      stmts.safe_push (use_stmt);
+	      top_stmt = use_stmt;
+	    }
+	  else if (dominated_by_p (CDI_DOMINATORS, bb, top_bb))
+	    stmts.safe_push (use_stmt);
+	  else
+	    continue;
+
+	  if (gimple_assign_rhs_code (use_stmt) == TRUNC_DIV_EXPR)
+	    div_seen = true;
+	}
+    }
+
+  if (!div_seen) 
+    return false;
+
+  /* Create libcall to internal fn DIVMOD:
+     divmod_tmp = DIVMOD (op1, op2).  */
+
+  gcall *call_stmt = gimple_build_call_internal (IFN_DIVMOD, 2, op1, op2);
+  tree res = make_temp_ssa_name (
+		build_complex_type (TREE_TYPE (op1)),
+		call_stmt, "divmod_tmp");
+  gimple_call_set_lhs (call_stmt, res);
+
+  /* Insert the call before top_stmt.  */
+  gimple_stmt_iterator top_stmt_gsi = gsi_for_stmt (top_stmt);
+  gsi_insert_before (&top_stmt_gsi, call_stmt, GSI_SAME_STMT);
+
+  widen_mul_stats.divmod_calls_inserted++;		
+
+  /* Update all statements in stmts.
+     if stmt is lhs = op1 TRUNC_DIV_EXPR op2, change to lhs = REALPART_EXPR<divmod_tmp>
+     if stmt is lhs = op1 TRUNC_MOD_EXPR op2, change to lhs = IMAGPART_EXPR<divmod_tmp>.  */
+
+  bool cfg_changed = false;
+  for (unsigned i = 0; stmts.iterate (i, &use_stmt); ++i)
+    {
+      tree new_rhs;
+
+      switch (gimple_assign_rhs_code (use_stmt))
+	{
+	  case TRUNC_DIV_EXPR:
+	    new_rhs = fold_build1 (REALPART_EXPR, TREE_TYPE (op1), res);
+	    break;
+
+	  case TRUNC_MOD_EXPR:
+	    new_rhs = fold_build1 (IMAGPART_EXPR, TREE_TYPE (op2), res);
+	    break;
+
+	  default:
+	    gcc_unreachable ();
+	}
+
+      gimple_stmt_iterator gsi = gsi_for_stmt (use_stmt);
+      gimple_assign_set_rhs_from_tree (&gsi, new_rhs);
+      update_stmt (use_stmt);
+
+      if (maybe_clean_or_replace_eh_stmt (use_stmt, use_stmt))
+	cfg_changed = true;
+    }
+
+  stmts.release ();
+  return cfg_changed;
+}    
 
 /* Find integer multiplications where the operands are extended from
    smaller types, and replace the MULT_EXPR with a WIDEN_MULT_EXPR
@@ -3828,6 +4024,8 @@ pass_optimize_widening_mul::execute (function *fun)
   bool cfg_changed = false;
 
   memset (&widen_mul_stats, 0, sizeof (widen_mul_stats));
+  calculate_dominance_info (CDI_DOMINATORS);
+  renumber_gimple_stmt_uids ();
 
   FOR_EACH_BB_FN (bb, fun)
     {
@@ -3861,6 +4059,10 @@ pass_optimize_widening_mul::execute (function *fun)
 		    match_uaddsub_overflow (&gsi, stmt, code);
 		  break;
 
+		case TRUNC_MOD_EXPR:
+		  cfg_changed = convert_to_divmod (as_a<gassign *> (stmt));
+		  break;
+
 		default:;
 		}
 	    }
@@ -3907,6 +4109,8 @@ pass_optimize_widening_mul::execute (function *fun)
 			    widen_mul_stats.maccs_inserted);
   statistics_counter_event (fun, "fused multiply-adds inserted",
 			    widen_mul_stats.fmas_inserted);
+  statistics_counter_event (fun, "divmod calls inserted",
+			    widen_mul_stats.divmod_calls_inserted);
 
   return cfg_changed ? TODO_cleanup_cfg : 0;
 }