[gcc r13-3374] expr: Fix ICE on BFmode -> SFmode conversion of constant [PR107262]

[gcc r13-3374] expr: Fix ICE on BFmode -> SFmode conversion of constant [PR107262]

[Jakub Jelinek]

https://gcc.gnu.org/g:65b98fc763d14d371fcf37a17e33519012ec2bac

commit r13-3374-g65b98fc763d14d371fcf37a17e33519012ec2bac
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Oct 19 11:29:44 2022 +0200

    expr: Fix ICE on BFmode -> SFmode conversion of constant [PR107262]
    
    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.
    
    2022-10-19  Jakub Jelinek  <jakub@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.

Diff:
---
 gcc/expr.cc                     | 11 +++++++++--
 gcc/testsuite/gcc.dg/pr107262.c | 13 +++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/gcc/expr.cc b/gcc/expr.cc
index 4c892d69249..efe387e6173 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -416,8 +416,15 @@ convert_mode_scalar (rtx to, rtx from, int unsignedp)
 		  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)
diff --git a/gcc/testsuite/gcc.dg/pr107262.c b/gcc/testsuite/gcc.dg/pr107262.c
new file mode 100644
index 00000000000..2ced0474645
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr107262.c
@@ -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;
+}