[36/77] Use scalar_int_mode in the RTL iv routines

This patch changes the iv modes in rtx_iv from machine_mode
to scalar_int_mode.  It also passes the mode of the iv down
to subroutines; this avoids the previous situation in which
the mode information was sometimes lost and had to be added
by the caller on return.

Some routines already took a mode argument, but the patch
tries to standardise on passing it immediately before the
argument it describes.

gcc/
2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

	* cfgloop.h (rtx_iv): Change type of extend_mode and mode to
	scalar_int_mode.
	(niter_desc): Likewise mode.
	(iv_analyze): Add a mode parameter.
	(biv_p): Likewise.
	(iv_analyze_expr): Pass the mode paraeter before the rtx it describes
	and change its type to scalar_int_mode.
	* loop-iv.c: Update commentary at head of file.
	(iv_constant): Pass the mode paraeter before the rtx it describes
	and change its type to scalar_int_mode.  Remove VOIDmode handling.
	(iv_subreg): Change the type of the mode parameter to scalar_int_mode.
	(iv_extend): Likewise.
	(shorten_into_mode): Likewise.
	(iv_add): Use scalar_int_mode.
	(iv_mult): Likewise.
	(iv_shift): Likewise.
	(canonicalize_iv_subregs): Likewise.
	(get_biv_step_1): Pass the outer_mode parameter before the rtx
	it describes and change its mode to scalar_int_mode.   Also change
	the type of the returned inner_mode to scalar_int_mode.
	(get_biv_step): Likewise, turning outer_mode from a pointer
	into a direct parameter.  Update call to get_biv_step_1.
	(iv_analyze_biv): Add an outer_mode parameter.  Update calls to
	iv_constant and get_biv_step.
	(iv_analyze_expr): Pass the mode parameter before the rtx it describes
	and change its type to scalar_int_mode.  Don't initialise iv->mode
	to VOIDmode and remove later checks for its still being VOIDmode.
	Update calls to iv_analyze_op and iv_analyze_expr.  Check
	is_a <scalar_int_mode> when changing the mode under consideration.
	(iv_analyze_def): Ignore registers that don't have a scalar_int_mode.
	Update call to iv_analyze_expr.
	(iv_analyze_op): Add a mode parameter.  Reject subregs whose
	inner register is not also a scalar_int_mode.  Update call to
	iv_analyze_biv.
	(iv_analyze): Add a mode parameter.  Update call to iv_analyze_op.
	(biv_p): Add a mode parameter.  Update call to iv_analyze_biv.
	(iv_number_of_iterations): Use is_a <scalar_int_mode> instead of
	separate mode class checks.  Update calls to iv_analyze.  Remove
	fix-up of VOIDmodes after iv_analyze_biv.
	* loop-unroll.c (analyze_iv_to_split_insn): Reject registers that
	don't have a scalar_int_mode.  Update call to biv_p.

From-SVN: r251488

3 files changed, 85 insertions, 95 deletions

diff --git a/gcc/cfgloop.h b/gcc/cfgloop.h
index e7ffa236437..fcf366745df 100644
--- a/gcc/cfgloop.h
+++ b/gcc/cfgloop.h
@@ -421,10 +421,10 @@ struct rtx_iv
   rtx delta, mult;
 
   /* The mode it is extended to.  */
-  machine_mode extend_mode;
+  scalar_int_mode extend_mode;
 
   /* The mode the variable iterates in.  */
-  machine_mode mode;
+  scalar_int_mode mode;
 
   /* Whether the first iteration needs to be handled specially.  */
   unsigned first_special : 1;
@@ -465,19 +465,19 @@ struct GTY(()) niter_desc
   bool signed_p;
 
   /* The mode in that niter_expr should be computed.  */
-  machine_mode mode;
+  scalar_int_mode mode;
 
   /* The number of iterations of the loop.  */
   rtx niter_expr;
 };
 
 extern void iv_analysis_loop_init (struct loop *);
-extern bool iv_analyze (rtx_insn *, rtx, struct rtx_iv *);
+extern bool iv_analyze (rtx_insn *, scalar_int_mode, rtx, struct rtx_iv *);
 extern bool iv_analyze_result (rtx_insn *, rtx, struct rtx_iv *);
-extern bool iv_analyze_expr (rtx_insn *, rtx, machine_mode,
+extern bool iv_analyze_expr (rtx_insn *, scalar_int_mode, rtx,
 			     struct rtx_iv *);
 extern rtx get_iv_value (struct rtx_iv *, rtx);
-extern bool biv_p (rtx_insn *, rtx);
+extern bool biv_p (rtx_insn *, scalar_int_mode, rtx);
 extern void find_simple_exit (struct loop *, struct niter_desc *);
 extern void iv_analysis_done (void);
 
diff --git a/gcc/loop-iv.c b/gcc/loop-iv.c
index 61074e3fb1a..1d0c66f2b2f 100644
--- a/gcc/loop-iv.c
+++ b/gcc/loop-iv.c
@@ -35,16 +35,17 @@ along with GCC; see the file COPYING3.  If not see
 
    The available functions are:
 
-   iv_analyze (insn, reg, iv): Stores the description of the induction variable
-     corresponding to the use of register REG in INSN to IV.  Returns true if
-     REG is an induction variable in INSN. false otherwise.
-     If use of REG is not found in INSN, following insns are scanned (so that
-     we may call this function on insn returned by get_condition).
+   iv_analyze (insn, mode, reg, iv): Stores the description of the induction
+     variable corresponding to the use of register REG in INSN to IV, given
+     that REG has mode MODE.  Returns true if REG is an induction variable
+     in INSN. false otherwise.  If a use of REG is not found in INSN,
+     the following insns are scanned (so that we may call this function
+     on insns returned by get_condition).
    iv_analyze_result (insn, def, iv):  Stores to IV the description of the iv
      corresponding to DEF, which is a register defined in INSN.
-   iv_analyze_expr (insn, rhs, mode, iv):  Stores to IV the description of iv
+   iv_analyze_expr (insn, mode, expr, iv):  Stores to IV the description of iv
      corresponding to expression EXPR evaluated at INSN.  All registers used bu
-     EXPR must also be used in INSN.
+     EXPR must also be used in INSN.  MODE is the mode of EXPR.
 */
 
 #include "config.h"
@@ -133,7 +134,7 @@ biv_entry_hasher::equal (const biv_entry *b, const rtx_def *r)
 
 static hash_table<biv_entry_hasher> *bivs;
 
-static bool iv_analyze_op (rtx_insn *, rtx, struct rtx_iv *);
+static bool iv_analyze_op (rtx_insn *, scalar_int_mode, rtx, struct rtx_iv *);
 
 /* Return the RTX code corresponding to the IV extend code EXTEND.  */
 static inline enum rtx_code
@@ -383,11 +384,8 @@ iv_get_reaching_def (rtx_insn *insn, rtx reg, df_ref *def)
    consistency with other iv manipulation functions that may fail).  */
 
 static bool
-iv_constant (struct rtx_iv *iv, rtx cst, machine_mode mode)
+iv_constant (struct rtx_iv *iv, scalar_int_mode mode, rtx cst)
 {
-  if (mode == VOIDmode)
-    mode = GET_MODE (cst);
-
   iv->mode = mode;
   iv->base = cst;
   iv->step = const0_rtx;
@@ -403,7 +401,7 @@ iv_constant (struct rtx_iv *iv, rtx cst, machine_mode mode)
 /* Evaluates application of subreg to MODE on IV.  */
 
 static bool
-iv_subreg (struct rtx_iv *iv, machine_mode mode)
+iv_subreg (struct rtx_iv *iv, scalar_int_mode mode)
 {
   /* If iv is invariant, just calculate the new value.  */
   if (iv->step == const0_rtx
@@ -445,7 +443,7 @@ iv_subreg (struct rtx_iv *iv, machine_mode mode)
 /* Evaluates application of EXTEND to MODE on IV.  */
 
 static bool
-iv_extend (struct rtx_iv *iv, enum iv_extend_code extend, machine_mode mode)
+iv_extend (struct rtx_iv *iv, enum iv_extend_code extend, scalar_int_mode mode)
 {
   /* If iv is invariant, just calculate the new value.  */
   if (iv->step == const0_rtx
@@ -508,7 +506,7 @@ iv_neg (struct rtx_iv *iv)
 static bool
 iv_add (struct rtx_iv *iv0, struct rtx_iv *iv1, enum rtx_code op)
 {
-  machine_mode mode;
+  scalar_int_mode mode;
   rtx arg;
 
   /* Extend the constant to extend_mode of the other operand if necessary.  */
@@ -578,7 +576,7 @@ iv_add (struct rtx_iv *iv0, struct rtx_iv *iv1, enum rtx_code op)
 static bool
 iv_mult (struct rtx_iv *iv, rtx mby)
 {
-  machine_mode mode = iv->extend_mode;
+  scalar_int_mode mode = iv->extend_mode;
 
   if (GET_MODE (mby) != VOIDmode
       && GET_MODE (mby) != mode)
@@ -603,7 +601,7 @@ iv_mult (struct rtx_iv *iv, rtx mby)
 static bool
 iv_shift (struct rtx_iv *iv, rtx mby)
 {
-  machine_mode mode = iv->extend_mode;
+  scalar_int_mode mode = iv->extend_mode;
 
   if (GET_MODE (mby) != VOIDmode
       && GET_MODE (mby) != mode)
@@ -628,9 +626,9 @@ iv_shift (struct rtx_iv *iv, rtx mby)
    at get_biv_step.  */
 
 static bool
-get_biv_step_1 (df_ref def, rtx reg,
-		rtx *inner_step, machine_mode *inner_mode,
-		enum iv_extend_code *extend, machine_mode outer_mode,
+get_biv_step_1 (df_ref def, scalar_int_mode outer_mode, rtx reg,
+		rtx *inner_step, scalar_int_mode *inner_mode,
+		enum iv_extend_code *extend,
 		rtx *outer_step)
 {
   rtx set, rhs, op0 = NULL_RTX, op1 = NULL_RTX;
@@ -732,8 +730,8 @@ get_biv_step_1 (df_ref def, rtx reg,
       *inner_mode = outer_mode;
       *outer_step = const0_rtx;
     }
-  else if (!get_biv_step_1 (next_def, reg,
-			    inner_step, inner_mode, extend, outer_mode,
+  else if (!get_biv_step_1 (next_def, outer_mode, reg,
+			    inner_step, inner_mode, extend,
 			    outer_step))
     return false;
 
@@ -793,19 +791,17 @@ get_biv_step_1 (df_ref def, rtx reg,
    LAST_DEF is the definition of REG that dominates loop latch.  */
 
 static bool
-get_biv_step (df_ref last_def, rtx reg, rtx *inner_step,
-	      machine_mode *inner_mode, enum iv_extend_code *extend,
-	      machine_mode *outer_mode, rtx *outer_step)
+get_biv_step (df_ref last_def, scalar_int_mode outer_mode, rtx reg,
+	      rtx *inner_step, scalar_int_mode *inner_mode,
+	      enum iv_extend_code *extend, rtx *outer_step)
 {
-  *outer_mode = GET_MODE (reg);
-
-  if (!get_biv_step_1 (last_def, reg,
-		       inner_step, inner_mode, extend, *outer_mode,
+  if (!get_biv_step_1 (last_def, outer_mode, reg,
+		       inner_step, inner_mode, extend,
 		       outer_step))
     return false;
 
-  gcc_assert ((*inner_mode == *outer_mode) != (*extend != IV_UNKNOWN_EXTEND));
-  gcc_assert (*inner_mode != *outer_mode || *outer_step == const0_rtx);
+  gcc_assert ((*inner_mode == outer_mode) != (*extend != IV_UNKNOWN_EXTEND));
+  gcc_assert (*inner_mode != outer_mode || *outer_step == const0_rtx);
 
   return true;
 }
@@ -850,13 +846,13 @@ record_biv (rtx def, struct rtx_iv *iv)
 }
 
 /* Determines whether DEF is a biv and if so, stores its description
-   to *IV.  */
+   to *IV.  OUTER_MODE is the mode of DEF.  */
 
 static bool
-iv_analyze_biv (rtx def, struct rtx_iv *iv)
+iv_analyze_biv (scalar_int_mode outer_mode, rtx def, struct rtx_iv *iv)
 {
   rtx inner_step, outer_step;
-  machine_mode inner_mode, outer_mode;
+  scalar_int_mode inner_mode;
   enum iv_extend_code extend;
   df_ref last_def;
 
@@ -872,7 +868,7 @@ iv_analyze_biv (rtx def, struct rtx_iv *iv)
       if (!CONSTANT_P (def))
 	return false;
 
-      return iv_constant (iv, def, VOIDmode);
+      return iv_constant (iv, outer_mode, def);
     }
 
   if (!latch_dominating_def (def, &last_def))
@@ -883,7 +879,7 @@ iv_analyze_biv (rtx def, struct rtx_iv *iv)
     }
 
   if (!last_def)
-    return iv_constant (iv, def, VOIDmode);
+    return iv_constant (iv, outer_mode, def);
 
   if (analyzed_for_bivness_p (def, iv))
     {
@@ -892,8 +888,8 @@ iv_analyze_biv (rtx def, struct rtx_iv *iv)
       return iv->base != NULL_RTX;
     }
 
-  if (!get_biv_step (last_def, def, &inner_step, &inner_mode, &extend,
-		     &outer_mode, &outer_step))
+  if (!get_biv_step (last_def, outer_mode, def, &inner_step, &inner_mode,
+		     &extend, &outer_step))
     {
       iv->base = NULL_RTX;
       goto end;
@@ -930,16 +926,15 @@ iv_analyze_biv (rtx def, struct rtx_iv *iv)
    The mode of the induction variable is MODE.  */
 
 bool
-iv_analyze_expr (rtx_insn *insn, rtx rhs, machine_mode mode,
+iv_analyze_expr (rtx_insn *insn, scalar_int_mode mode, rtx rhs,
 		 struct rtx_iv *iv)
 {
   rtx mby = NULL_RTX;
   rtx op0 = NULL_RTX, op1 = NULL_RTX;
   struct rtx_iv iv0, iv1;
   enum rtx_code code = GET_CODE (rhs);
-  machine_mode omode = mode;
+  scalar_int_mode omode = mode;
 
-  iv->mode = VOIDmode;
   iv->base = NULL_RTX;
   iv->step = NULL_RTX;
 
@@ -948,18 +943,7 @@ iv_analyze_expr (rtx_insn *insn, rtx rhs, machine_mode mode,
   if (CONSTANT_P (rhs)
       || REG_P (rhs)
       || code == SUBREG)
-    {
-      if (!iv_analyze_op (insn, rhs, iv))
-	return false;
-
-      if (iv->mode == VOIDmode)
-	{
-	  iv->mode = mode;
-	  iv->extend_mode = mode;
-	}
-
-      return true;
-    }
+    return iv_analyze_op (insn, mode, rhs, iv);
 
   switch (code)
     {
@@ -971,7 +955,9 @@ iv_analyze_expr (rtx_insn *insn, rtx rhs, machine_mode mode,
     case ZERO_EXTEND:
     case NEG:
       op0 = XEXP (rhs, 0);
-      omode = GET_MODE (op0);
+      /* We don't know how many bits there are in a sign-extended constant.  */
+      if (!is_a <scalar_int_mode> (GET_MODE (op0), &omode))
+	return false;
       break;
 
     case PLUS:
@@ -1001,11 +987,11 @@ iv_analyze_expr (rtx_insn *insn, rtx rhs, machine_mode mode,
     }
 
   if (op0
-      && !iv_analyze_expr (insn, op0, omode, &iv0))
+      && !iv_analyze_expr (insn, omode, op0, &iv0))
     return false;
 
   if (op1
-      && !iv_analyze_expr (insn, op1, omode, &iv1))
+      && !iv_analyze_expr (insn, omode, op1, &iv1))
     return false;
 
   switch (code)
@@ -1075,11 +1061,11 @@ iv_analyze_def (df_ref def, struct rtx_iv *iv)
       return iv->base != NULL_RTX;
     }
 
-  iv->mode = VOIDmode;
   iv->base = NULL_RTX;
   iv->step = NULL_RTX;
 
-  if (!REG_P (reg))
+  scalar_int_mode mode;
+  if (!REG_P (reg) || !is_a <scalar_int_mode> (GET_MODE (reg), &mode))
     return false;
 
   set = single_set (insn);
@@ -1096,7 +1082,7 @@ iv_analyze_def (df_ref def, struct rtx_iv *iv)
   else
     rhs = SET_SRC (set);
 
-  iv_analyze_expr (insn, rhs, GET_MODE (reg), iv);
+  iv_analyze_expr (insn, mode, rhs, iv);
   record_iv (def, iv);
 
   if (dump_file)
@@ -1112,10 +1098,11 @@ iv_analyze_def (df_ref def, struct rtx_iv *iv)
   return iv->base != NULL_RTX;
 }
 
-/* Analyzes operand OP of INSN and stores the result to *IV.  */
+/* Analyzes operand OP of INSN and stores the result to *IV.  MODE is the
+   mode of OP.  */
 
 static bool
-iv_analyze_op (rtx_insn *insn, rtx op, struct rtx_iv *iv)
+iv_analyze_op (rtx_insn *insn, scalar_int_mode mode, rtx op, struct rtx_iv *iv)
 {
   df_ref def = NULL;
   enum iv_grd_result res;
@@ -1132,13 +1119,15 @@ iv_analyze_op (rtx_insn *insn, rtx op, struct rtx_iv *iv)
     res = GRD_INVARIANT;
   else if (GET_CODE (op) == SUBREG)
     {
-      if (!subreg_lowpart_p (op))
+      scalar_int_mode inner_mode;
+      if (!subreg_lowpart_p (op)
+	  || !is_a <scalar_int_mode> (GET_MODE (SUBREG_REG (op)), &inner_mode))
 	return false;
 
-      if (!iv_analyze_op (insn, SUBREG_REG (op), iv))
+      if (!iv_analyze_op (insn, inner_mode, SUBREG_REG (op), iv))
 	return false;
 
-      return iv_subreg (iv, GET_MODE (op));
+      return iv_subreg (iv, mode);
     }
   else
     {
@@ -1153,7 +1142,7 @@ iv_analyze_op (rtx_insn *insn, rtx op, struct rtx_iv *iv)
 
   if (res == GRD_INVARIANT)
     {
-      iv_constant (iv, op, VOIDmode);
+      iv_constant (iv, mode, op);
 
       if (dump_file)
 	{
@@ -1165,15 +1154,16 @@ iv_analyze_op (rtx_insn *insn, rtx op, struct rtx_iv *iv)
     }
 
   if (res == GRD_MAYBE_BIV)
-    return iv_analyze_biv (op, iv);
+    return iv_analyze_biv (mode, op, iv);
 
   return iv_analyze_def (def, iv);
 }
 
-/* Analyzes value VAL at INSN and stores the result to *IV.  */
+/* Analyzes value VAL at INSN and stores the result to *IV.  MODE is the
+   mode of VAL.  */
 
 bool
-iv_analyze (rtx_insn *insn, rtx val, struct rtx_iv *iv)
+iv_analyze (rtx_insn *insn, scalar_int_mode mode, rtx val, struct rtx_iv *iv)
 {
   rtx reg;
 
@@ -1192,7 +1182,7 @@ iv_analyze (rtx_insn *insn, rtx val, struct rtx_iv *iv)
 	insn = NEXT_INSN (insn);
     }
 
-  return iv_analyze_op (insn, val, iv);
+  return iv_analyze_op (insn, mode, val, iv);
 }
 
 /* Analyzes definition of DEF in INSN and stores the result to IV.  */
@@ -1210,11 +1200,13 @@ iv_analyze_result (rtx_insn *insn, rtx def, struct rtx_iv *iv)
 }
 
 /* Checks whether definition of register REG in INSN is a basic induction
-   variable.  IV analysis must have been initialized (via a call to
+   variable.  MODE is the mode of REG.
+
+   IV analysis must have been initialized (via a call to
    iv_analysis_loop_init) for this function to produce a result.  */
 
 bool
-biv_p (rtx_insn *insn, rtx reg)
+biv_p (rtx_insn *insn, scalar_int_mode mode, rtx reg)
 {
   struct rtx_iv iv;
   df_ref def, last_def;
@@ -1229,7 +1221,7 @@ biv_p (rtx_insn *insn, rtx reg)
   if (last_def != def)
     return false;
 
-  if (!iv_analyze_biv (reg, &iv))
+  if (!iv_analyze_biv (mode, reg, &iv))
     return false;
 
   return iv.step != const0_rtx;
@@ -2078,7 +2070,7 @@ simplify_using_initial_values (struct loop *loop, enum rtx_code op, rtx *expr)
    is SIGNED_P to DESC.  */
 
 static void
-shorten_into_mode (struct rtx_iv *iv, machine_mode mode,
+shorten_into_mode (struct rtx_iv *iv, scalar_int_mode mode,
 		   enum rtx_code cond, bool signed_p, struct niter_desc *desc)
 {
   rtx mmin, mmax, cond_over, cond_under;
@@ -2140,7 +2132,7 @@ static bool
 canonicalize_iv_subregs (struct rtx_iv *iv0, struct rtx_iv *iv1,
 			 enum rtx_code cond, struct niter_desc *desc)
 {
-  machine_mode comp_mode;
+  scalar_int_mode comp_mode;
   bool signed_p;
 
   /* If the ivs behave specially in the first iteration, or are
@@ -2318,7 +2310,8 @@ iv_number_of_iterations (struct loop *loop, rtx_insn *insn, rtx condition,
   struct rtx_iv iv0, iv1;
   rtx assumption, may_not_xform;
   enum rtx_code cond;
-  machine_mode mode, comp_mode;
+  machine_mode nonvoid_mode;
+  scalar_int_mode comp_mode;
   rtx mmin, mmax, mode_mmin, mode_mmax;
   uint64_t s, size, d, inv, max, up, down;
   int64_t inc, step_val;
@@ -2343,28 +2336,24 @@ iv_number_of_iterations (struct loop *loop, rtx_insn *insn, rtx condition,
   cond = GET_CODE (condition);
   gcc_assert (COMPARISON_P (condition));
 
-  mode = GET_MODE (XEXP (condition, 0));
-  if (mode == VOIDmode)
-    mode = GET_MODE (XEXP (condition, 1));
+  nonvoid_mode = GET_MODE (XEXP (condition, 0));
+  if (nonvoid_mode == VOIDmode)
+    nonvoid_mode = GET_MODE (XEXP (condition, 1));
   /* The constant comparisons should be folded.  */
-  gcc_assert (mode != VOIDmode);
+  gcc_assert (nonvoid_mode != VOIDmode);
 
   /* We only handle integers or pointers.  */
-  if (GET_MODE_CLASS (mode) != MODE_INT
-      && GET_MODE_CLASS (mode) != MODE_PARTIAL_INT)
+  scalar_int_mode mode;
+  if (!is_a <scalar_int_mode> (nonvoid_mode, &mode))
     goto fail;
 
   op0 = XEXP (condition, 0);
-  if (!iv_analyze (insn, op0, &iv0))
+  if (!iv_analyze (insn, mode, op0, &iv0))
     goto fail;
-  if (iv0.extend_mode == VOIDmode)
-    iv0.mode = iv0.extend_mode = mode;
 
   op1 = XEXP (condition, 1);
-  if (!iv_analyze (insn, op1, &iv1))
+  if (!iv_analyze (insn, mode, op1, &iv1))
     goto fail;
-  if (iv1.extend_mode == VOIDmode)
-    iv1.mode = iv1.extend_mode = mode;
 
   if (GET_MODE_BITSIZE (iv0.extend_mode) > HOST_BITS_PER_WIDE_INT
       || GET_MODE_BITSIZE (iv1.extend_mode) > HOST_BITS_PER_WIDE_INT)
diff --git a/gcc/loop-unroll.c b/gcc/loop-unroll.c
index 84145bb4a4f..8cf305b24c5 100644
--- a/gcc/loop-unroll.c
+++ b/gcc/loop-unroll.c
@@ -1509,6 +1509,7 @@ analyze_iv_to_split_insn (rtx_insn *insn)
   rtx set, dest;
   struct rtx_iv iv;
   struct iv_to_split *ivts;
+  scalar_int_mode mode;
   bool ok;
 
   /* For now we just split the basic induction variables.  Later this may be
@@ -1518,10 +1519,10 @@ analyze_iv_to_split_insn (rtx_insn *insn)
     return NULL;
 
   dest = SET_DEST (set);
-  if (!REG_P (dest))
+  if (!REG_P (dest) || !is_a <scalar_int_mode> (GET_MODE (dest), &mode))
     return NULL;
 
-  if (!biv_p (insn, dest))
+  if (!biv_p (insn, mode, dest))
     return NULL;
 
   ok = iv_analyze_result (insn, dest, &iv);