On Wed, 11 Feb 2026, Tamar Christina wrote:
> There were two mutually incompatible changes reviewed and
> merged around the same time for different issues in
> convert_mult_to_fma.
>
> the change in r16-7353 keeps result in it's unpromoted form
> and deals with it as such but the change in r16-7304 expects
> it to be in it's promoted form.
>
> This causes the assert to fail again and the SVE testcase I
> added before to fail.
>
> Since the value is now kept in it's unpromoted form, and result
> is not used as any LHS side, I've partially reverted the
> convert stripping to make use of it.
>
> I also added a RVV testcase this time as well.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu,
> arm-none-linux-gnueabihf, x86_64-pc-linux-gnu
> -m32, -m64 and no issues.
>
> And tested manually on RVV.
>
> Ok for master?
OK.
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> PR tree-optimization/124038
> * tree-ssa-math-opts.cc (strip_nop_view_converts): Remove.
> (convert_mult_to_fma): Undo stripping.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/124038
> * gcc.target/riscv/rvv/pr124038.c: New test.
>
> ---
> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/pr124038.c
> b/gcc/testsuite/gcc.target/riscv/rvv/pr124038.c
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..0f8075b0fbda59a41fc4638119e3f5f3dfbfffee
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/pr124038.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 --param=avoid-fma-max-bits=8 -march=rv64gv
> -fdump-tree-widening_mul" } */
> +
> +typedef __attribute__((__vector_size__(1))) unsigned char U;
> +typedef __attribute__((__vector_size__(1))) signed char V;
> +
> +U u;
> +signed char c;
> +
> +U
> +foo(V v)
> +{
> + v *= c;
> + return u + v;
> +}
> +
> +/* { dg-final { scan-tree-dump "FMA" "widening_mul" } } */
> diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
> index
> 6d69711fffbd5d12f5ef4e216e7db134ba8ee490..bb67dca560b419d2bcbdeb6d3bb626eb1bad73d2
> 100644
> --- a/gcc/tree-ssa-math-opts.cc
> +++ b/gcc/tree-ssa-math-opts.cc
> @@ -118,7 +118,6 @@ along with GCC; see the file COPYING3. If not see
> #include "tree-ssa-math-opts.h"
> #include "dbgcnt.h"
> #include "cfghooks.h"
> -#include "gimple-match.h"
>
> /* This structure represents one basic block that either computes a
> division, or is a common dominator for basic block that compute a
> @@ -3357,26 +3356,6 @@ last_fma_candidate_feeds_initial_phi
> (fma_deferring_state *state,
> return false;
> }
>
> -/* If ARG is a convert that only changes the sign then strip the outer
> - conversion away. It does not strip conversions recursively. Otherwise
> - return ARG. */
> -
> -static tree
> -strip_nop_view_converts (tree arg)
> -{
> - if (TREE_CODE (arg) != SSA_NAME)
> - return arg;
> -
> - gimple *assign = SSA_NAME_DEF_STMT (arg);
> - gimple_match_op res_op;
> - if (gimple_extract_op (assign, &res_op)
> - && (CONVERT_EXPR_CODE_P (res_op.code) || res_op.code ==
> VIEW_CONVERT_EXPR)
> - && tree_nop_conversion_p (TREE_TYPE (res_op.ops[0]), TREE_TYPE (arg)))
> - return res_op.ops[0];
> -
> - return arg;
> -}
> -
> /* Combine the multiplication at MUL_STMT with operands MULOP1 and MULOP2
> with uses in additions and subtractions to form fused multiply-add
> operations. Returns true if successful and MUL_STMT should be removed.
> @@ -3642,11 +3621,11 @@ convert_mult_to_fma (gimple *mul_stmt, tree op1, tree
> op2,
> {
> gcc_checking_assert (!state->m_initial_phi);
> gphi *phi;
> - if (strip_nop_view_converts (ops[0]) == result)
> + if (ops[0] == result)
> phi = result_of_phi (ops[1]);
> else
> {
> - gcc_assert (strip_nop_view_converts (ops[1]) == result);
> + gcc_assert (ops[1] == result);
> phi = result_of_phi (ops[0]);
> }
>
>
>
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
