[PATCH] i386: Handle unsupported modes from ix86_widen_mult_cost [PR109807]

[Uros Bizjak]

Revert my previous change that faked handling of V4HI and V2SImodes
in ix86_widen_mult_cost and rather return arbitrary high value
for unsupported modes. This should prevent cost estimator from
selecting non-existent vector widen multiply operation.

gcc/ChangeLog:

    PR target/109807
    * config/i386/i386.cc: Revert the 2023-05-11 change.
    (ix86_widen_mult_cost): Return high value instead of
    ICEing for unsupported modes.

gcc/testsuite/ChangeLog:

    PR target/109807
    * gcc.target/i386/pr109825.c: New test.

Bootstrapped and regression tested on x86_64-linux-gnu {,--m32}.

Pushed to master.

Uros.
-------------- next part --------------
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 4011203486b..498fac468b5 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -20417,14 +20417,12 @@ ix86_widen_mult_cost (const struct processor_costs *cost,
   int basic_cost = 0;
   switch (mode)
     {
-    case V4HImode:
     case V8HImode:
     case V16HImode:
       if (!uns_p || mode == V16HImode)
 	extra_cost = cost->sse_op * 2;
       basic_cost = cost->mulss * 2 + cost->sse_op * 4;
       break;
-    case V2SImode:
     case V4SImode:
     case V8SImode:
       /* pmulhw/pmullw can be used.  */
@@ -20441,7 +20439,8 @@ ix86_widen_mult_cost (const struct processor_costs *cost,
       basic_cost = cost->mulss * 2 + cost->sse_op * 4;
       break;
     default:
-      gcc_unreachable();
+      /* Not implemented.  */
+      return 100;
     }
   return ix86_vec_cost (mode, basic_cost + extra_cost);
 }
diff --git a/gcc/testsuite/gcc.target/i386/pr109825.c b/gcc/testsuite/gcc.target/i386/pr109825.c
new file mode 100644
index 00000000000..a8f7ca94641
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr109825.c
@@ -0,0 +1,4 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-Os -ftree-slp-vectorize -mavx512vl" } */
+
+#include "../../gcc.dg/vect/slp-widen-mult-u8.c"