[PATCH] expr: Fix ICE on BFmode -> SFmode conversion of constant [PR107262]

[Jakub Jelinek via Gcc-patches]

Hi!

I forgot to handle the case where lowpart_subreg returns a VOIDmode
CONST_INT, in that case convert_mode_scalar obviously doesn't work.

The following patch fixes that.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2022-10-19  Jakub Jelinek  <ja...@redhat.com>

        PR middle-end/107262
        * expr.cc (convert_mode_scalar): For BFmode -> SFmode conversions
        of constants, use simplify_unary_operation if fromi has VOIDmode
        instead of recursive convert_mode_scalar.

        * gcc.dg/pr107262.c: New test.

--- gcc/expr.cc.jj      2022-10-14 09:35:56.134991155 +0200
+++ gcc/expr.cc 2022-10-18 14:07:24.330512745 +0200
@@ -416,8 +416,15 @@ convert_mode_scalar (rtx to, rtx from, i
                  rtx tof = NULL_RTX;
                  if (fromi)
                    {
-                     rtx toi = gen_reg_rtx (toi_mode);
-                     convert_mode_scalar (toi, fromi, 1);
+                     rtx toi;
+                     if (GET_MODE (fromi) == VOIDmode)
+                       toi = simplify_unary_operation (ZERO_EXTEND, toi_mode,
+                                                       fromi, fromi_mode);
+                     else
+                       {
+                         toi = gen_reg_rtx (toi_mode);
+                         convert_mode_scalar (toi, fromi, 1);
+                       }
                      toi
                        = maybe_expand_shift (LSHIFT_EXPR, toi_mode, toi,
                                              GET_MODE_PRECISION (to_mode)
--- gcc/testsuite/gcc.dg/pr107262.c.jj  2022-10-18 14:09:44.114607505 +0200
+++ gcc/testsuite/gcc.dg/pr107262.c     2022-10-18 14:09:33.708749313 +0200
@@ -0,0 +1,13 @@
+/* PR middle-end/107262 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -ffast-math" } */
+/* { dg-add-options bfloat16 } */
+/* { dg-require-effective-target bfloat16_runtime } */
+
+__bf16
+foo (__bf16 a)
+{
+  __bf16 b = 0;
+  b /= a;
+  return b;
+}

        Jakub