[gcc(refs/vendors/riscv/heads/gcc-15-with-riscv-opts)] RISC-V: update prepare_ternary_operands to handle vector-scalar case [PR120828]

[Jeff Law]

https://gcc.gnu.org/g:c23468068f4ab052d59ca77180e551ed28ff9ae4

commit c23468068f4ab052d59ca77180e551ed28ff9ae4
Author: Paul-Antoine Arras <parras@baylibre.com>
Date:   Wed Jun 25 16:42:00 2025 +0000

    RISC-V: update prepare_ternary_operands to handle vector-scalar case [PR120828]
    
    This is a followup to 92e1893e0 "RISC-V: Add patterns for vector-scalar
    multiply-(subtract-)accumulate" that caused an ICE in some cases where the mult
    operands were wrongly swapped.
    This patch ensures that operands are not swapped in the vector-scalar case.
    
            PR target/120828
    
    gcc/ChangeLog:
    
            * config/riscv/riscv-v.cc (prepare_ternary_operands): Handle the
            vector-scalar case.
    
    (cherry picked from commit 181cb2943d53862aa41eab49a042dff991a3d94f)

Diff:
---
 gcc/config/riscv/riscv-v.cc | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/gcc/config/riscv/riscv-v.cc b/gcc/config/riscv/riscv-v.cc
index f2a830f0f0cf..8b03bd3d2397 100644
--- a/gcc/config/riscv/riscv-v.cc
+++ b/gcc/config/riscv/riscv-v.cc
@@ -4764,7 +4764,7 @@ prepare_ternary_operands (rtx *ops)
 				   ops[4], ops[1], ops[6], ops[7], ops[9]));
       ops[5] = ops[4] = ops[0];
     }
-  else
+  else if (VECTOR_MODE_P (GET_MODE (ops[2])))
     {
       /* Swap the multiplication ops if the fallback value is the
 	 second of the two.  */
@@ -4774,8 +4774,10 @@ prepare_ternary_operands (rtx *ops)
       /* TODO: ??? Maybe we could support splitting FMA (a, 4, b)
 	 into PLUS (ASHIFT (a, 2), b) according to uarchs.  */
     }
-  gcc_assert (rtx_equal_p (ops[5], RVV_VUNDEF (mode))
-	      || rtx_equal_p (ops[5], ops[2]) || rtx_equal_p (ops[5], ops[4]));
+  gcc_assert (
+    rtx_equal_p (ops[5], RVV_VUNDEF (mode)) || rtx_equal_p (ops[5], ops[2])
+    || (!VECTOR_MODE_P (GET_MODE (ops[2])) && rtx_equal_p (ops[5], ops[3]))
+    || rtx_equal_p (ops[5], ops[4]));
 }
 
 /* Expand VEC_MASK_LEN_{LOAD_LANES,STORE_LANES}.  */