From: H.J. Lu <hjl.tools@gmail.com>
Date: Fri, 3 Oct 2025 23:02:20 +0000 (+0800)
Subject: x86: Handle small OP size in setmem_epilogue_gen_val
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a3727eb5e821d6a1916805029aeaed092e5e739d;p=thirdparty%2Fgcc.git

x86: Handle small OP size in setmem_epilogue_gen_val

Since OP size passed to setmem_epilogue_gen_val may be smaller than the
required vector size, duplicate it first before setting vector.

gcc/

	PR target/122150
	* config/i386/i386-expand.cc (setmem_epilogue_gen_val): Duplicate
	OP if its size is smaller than MODE size.

gcc/testsuite/

	PR target/122150
	* gcc.target/i386/pr122150.c: New test.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
---

diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index c6f42275a3e..0115af4d359 100644
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -8443,9 +8443,28 @@ setmem_epilogue_gen_val (void *op_p, void *prev_p, HOST_WIDE_INT,
 
       unsigned int op_size = GET_MODE_SIZE (op_mode);
       unsigned int size = GET_MODE_SIZE (mode);
-      unsigned int nunits = op_size / GET_MODE_SIZE (QImode);
-      machine_mode vec_mode
-	= mode_for_vector (QImode, nunits).require ();
+      unsigned int nunits;
+      machine_mode vec_mode;
+      if (op_size < size)
+	{
+	  /* If OP size is smaller than MODE size, duplicate it.  */
+	  nunits = size / GET_MODE_SIZE (QImode);
+	  vec_mode = mode_for_vector (QImode, nunits).require ();
+	  nunits = size / op_size;
+	  gcc_assert (SCALAR_INT_MODE_P (op_mode));
+	  machine_mode dup_mode
+	    = mode_for_vector (as_a <scalar_mode> (op_mode),
+			       nunits).require ();
+	  target = gen_reg_rtx (vec_mode);
+	  op = gen_vec_duplicate (dup_mode, op);
+	  rtx dup_op = gen_reg_rtx (dup_mode);
+	  emit_move_insn (dup_op, op);
+	  op = gen_rtx_SUBREG (vec_mode, dup_op, 0);
+	  emit_move_insn (target, op);
+	  return target;
+	}
+      nunits = op_size / GET_MODE_SIZE (QImode);
+      vec_mode = mode_for_vector (QImode, nunits).require ();
       target = gen_reg_rtx (vec_mode);
       op = gen_rtx_SUBREG (vec_mode, op, 0);
       emit_move_insn (target, op);
diff --git a/gcc/testsuite/gcc.target/i386/pr122150.c b/gcc/testsuite/gcc.target/i386/pr122150.c
new file mode 100644
index 00000000000..973c34d180e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr122150.c
@@ -0,0 +1,21 @@
+/* { dg-do run } */
+/* { dg-options "-mstringop-strategy=unrolled_loop" } */
+
+char c[2841];
+
+__attribute__((noipa))
+void
+foo (void)
+{
+  __builtin_memset (&c, 1, 2841);
+}
+
+int
+main (void)
+{
+  foo ();
+  for (unsigned i = 0; i < sizeof (c); i++)
+    if (c[i] != 1)
+      __builtin_abort();
+  return 0;
+}