[PATCH] LoongArch: Use simplify_gen_subreg instead of gen_rtx_SUBREG in loongarch_expand_vec_cond_mask_expr [PR112476]

[Xi Ruoyao]

GCC internal says:

    'subreg's of 'subreg's are not supported.  Using
    'simplify_gen_subreg' is the recommended way to avoid this problem.

Unfortunately loongarch_expand_vec_cond_mask_expr might create nested
subreg under certain circumstances, causing an ICE.

Use simplify_gen_subreg as the internal document suggests.

gcc/ChangeLog:

        PR target/112476
        * config/loongarch/loongarch.cc
        (loongarch_expand_vec_cond_mask_expr): Call simplify_gen_subreg
        instead of gen_rtx_SUBREG.

gcc/testsuite/ChangeLog:

        PR target/112476
        * gcc.target/loongarch/pr112476-1.c: New test.
        * gcc.target/loongarch/pr112476-2.c: New test.
---

Bootstrapped and regtested on loongarch64-linux-gnu.  Ok for trunk?

 gcc/config/loongarch/loongarch.cc             | 11 ++++++---
 .../gcc.target/loongarch/pr112476-1.c         | 24 +++++++++++++++++++
 .../gcc.target/loongarch/pr112476-2.c         |  5 ++++
 3 files changed, 37 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/loongarch/pr112476-1.c
 create mode 100644 gcc/testsuite/gcc.target/loongarch/pr112476-2.c

diff --git a/gcc/config/loongarch/loongarch.cc 
b/gcc/config/loongarch/loongarch.cc
index d9b7a1076a2..0c7bafb5fb1 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -11197,7 +11197,9 @@ loongarch_expand_vec_cond_mask_expr (machine_mode mode, 
machine_mode vimode,
          if (mode != vimode)
            {
              xop1 = gen_reg_rtx (vimode);
-             emit_move_insn (xop1, gen_rtx_SUBREG (vimode, operands[1], 0));
+             emit_move_insn (xop1,
+                             simplify_gen_subreg (vimode, operands[1],
+                                                  mode, 0));
            }
          emit_move_insn (src1, xop1);
        }
@@ -11214,7 +11216,9 @@ loongarch_expand_vec_cond_mask_expr (machine_mode mode, 
machine_mode vimode,
          if (mode != vimode)
            {
              xop2 = gen_reg_rtx (vimode);
-             emit_move_insn (xop2, gen_rtx_SUBREG (vimode, operands[2], 0));
+             emit_move_insn (xop2,
+                             simplify_gen_subreg (vimode, operands[2],
+                                                  mode, 0));
            }
          emit_move_insn (src2, xop2);
        }
@@ -11233,7 +11237,8 @@ loongarch_expand_vec_cond_mask_expr (machine_mode mode, 
machine_mode vimode,
                          gen_rtx_AND (vimode, mask, src1));
       /* The result is placed back to a register with the mask.  */
       emit_insn (gen_rtx_SET (mask, bsel));
-      emit_move_insn (operands[0], gen_rtx_SUBREG (mode, mask, 0));
+      emit_move_insn (operands[0], simplify_gen_subreg (mode, mask,
+                                                       vimode, 0));
     }
 }
 
diff --git a/gcc/testsuite/gcc.target/loongarch/pr112476-1.c 
b/gcc/testsuite/gcc.target/loongarch/pr112476-1.c
new file mode 100644
index 00000000000..4cf133e7a26
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/pr112476-1.c
@@ -0,0 +1,24 @@
+/* PR target/112476: ICE with -mlsx */
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=loongarch64 -mfpu=64 -mabi=lp64d -mlsx" } */
+
+int foo, bar;
+float baz, res, a;
+
+void
+apply_adjacent_ternary (float *dst, float *src0)
+{
+  do
+    {
+      __builtin_memcpy (&res, &src0, sizeof (res));
+      *dst = foo ? baz : res;
+      dst++;
+    }
+  while (dst != src0);
+}
+
+void
+xx (void)
+{
+  apply_adjacent_ternary (&a, &a);
+}
diff --git a/gcc/testsuite/gcc.target/loongarch/pr112476-2.c 
b/gcc/testsuite/gcc.target/loongarch/pr112476-2.c
new file mode 100644
index 00000000000..cc0dfbfc912
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/pr112476-2.c
@@ -0,0 +1,5 @@
+/* PR target/112476: ICE with -mlasx */
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=loongarch64 -mfpu=64 -mabi=lp64d -mlasx" } */
+
+#include "pr112476-1.c"
-- 
2.42.1