From: Tamar Christina <tamar.christina@arm.com>
Date: Wed, 11 Feb 2026 11:36:50 +0000 (+0000)
Subject: middle-end: partially revert fix for PR123898 after fix for PR123940 [PR124038]
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cd0bab746909a76e5cb724fba8c7f4ddb194207a;p=thirdparty%2Fgcc.git

middle-end: partially revert fix for PR123898 after fix for PR123940 [PR124038]

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.

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 00000000000..7ecf6dd89e8
--- /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 -mabi=lp64d -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 6d69711fffb..bb67dca560b 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]);
 		}