[PATCH 2/3] expmed: Fix possible use of NULL_RTX return value from emit_store_flag

[Jozef Lawrynowicz]

MSP430 does not support have any store-flag instructions, so
emit_store_flag can return NULL_RTX.  Catch the NULL_RTX in
expmed.c:expand_sdiv_pow2.

Successfully regtested on trunk for x86_64-pc-linux-gnu and msp430-elf.
Ok to apply?

>From cb0f8219ac90229c0336281d73f511c107c877d3 Mon Sep 17 00:00:00 2001
From: Jozef Lawrynowicz <joze...@mittosystems.com>
Date: Wed, 15 Jul 2020 11:19:31 +0100
Subject: [PATCH 2/3] expmed: Fix possible use of NULL_RTX return value from
 emit_store_flag

MSP430 does not support have any store-flag instructions, so
emit_store_flag can return NULL_RTX.  Catch the NULL_RTX in
expmed.c:expand_sdiv_pow2.

gcc/ChangeLog:

        * expmed.c (expand_sdiv_pow2): Check return value from emit_store_flag
        is not NULL_RTX before use.

---
 gcc/expmed.c | 34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/gcc/expmed.c b/gcc/expmed.c
index e7c03fbf92c..d3a1735d39e 100644
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -4086,9 +4086,12 @@ expand_sdiv_pow2 (scalar_int_mode mode, rtx op0, 
HOST_WIDE_INT d)
     {
       temp = gen_reg_rtx (mode);
       temp = emit_store_flag (temp, LT, op0, const0_rtx, mode, 0, 1);
-      temp = expand_binop (mode, add_optab, temp, op0, NULL_RTX,
-                          0, OPTAB_LIB_WIDEN);
-      return expand_shift (RSHIFT_EXPR, mode, temp, logd, NULL_RTX, 0);
+      if (temp != NULL_RTX)
+       {
+         temp = expand_binop (mode, add_optab, temp, op0, NULL_RTX,
+                              0, OPTAB_LIB_WIDEN);
+         return expand_shift (RSHIFT_EXPR, mode, temp, logd, NULL_RTX, 0);
+       }
     }
 
   if (HAVE_conditional_move
@@ -4122,17 +4125,20 @@ expand_sdiv_pow2 (scalar_int_mode mode, rtx op0, 
HOST_WIDE_INT d)
 
       temp = gen_reg_rtx (mode);
       temp = emit_store_flag (temp, LT, op0, const0_rtx, mode, 0, -1);
-      if (GET_MODE_BITSIZE (mode) >= BITS_PER_WORD
-         || shift_cost (optimize_insn_for_speed_p (), mode, ushift)
-            > COSTS_N_INSNS (1))
-       temp = expand_binop (mode, and_optab, temp, gen_int_mode (d - 1, mode),
-                            NULL_RTX, 0, OPTAB_LIB_WIDEN);
-      else
-       temp = expand_shift (RSHIFT_EXPR, mode, temp,
-                            ushift, NULL_RTX, 1);
-      temp = expand_binop (mode, add_optab, temp, op0, NULL_RTX,
-                          0, OPTAB_LIB_WIDEN);
-      return expand_shift (RSHIFT_EXPR, mode, temp, logd, NULL_RTX, 0);
+      if (temp != NULL_RTX)
+       {
+         if (GET_MODE_BITSIZE (mode) >= BITS_PER_WORD
+             || shift_cost (optimize_insn_for_speed_p (), mode, ushift)
+             > COSTS_N_INSNS (1))
+           temp = expand_binop (mode, and_optab, temp, gen_int_mode (d - 1, 
mode),
+                                NULL_RTX, 0, OPTAB_LIB_WIDEN);
+         else
+           temp = expand_shift (RSHIFT_EXPR, mode, temp,
+                                ushift, NULL_RTX, 1);
+         temp = expand_binop (mode, add_optab, temp, op0, NULL_RTX,
+                              0, OPTAB_LIB_WIDEN);
+         return expand_shift (RSHIFT_EXPR, mode, temp, logd, NULL_RTX, 0);
+       }
     }
 
   label = gen_label_rtx ();
-- 
2.27.0