[PATCH] RISC-V: Fix incorrect mode tieable which cause ICE in RA[PR111296]

[Juzhe-Zhong <juzhe.zhong@rivai.ai>]

This patch fix incorrect mode tieable between DI and V2SI which cause ICE
in RA.

	PR target/111296

gcc/ChangeLog:

	* config/riscv/riscv.cc (riscv_modes_tieable_p): Fix bug.

gcc/testsuite/ChangeLog:

	* g++.target/riscv/rvv/base/pr111296.C: New test.

---
 gcc/config/riscv/riscv.cc                      |  7 +++++++
 .../g++.target/riscv/rvv/base/pr111296.C       | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 gcc/testsuite/g++.target/riscv/rvv/base/pr111296.C

diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 228515acc1f..2c0c4c2f3ae 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -7648,6 +7648,13 @@ riscv_hard_regno_mode_ok (unsigned int regno, machine_mode mode)
 static bool
 riscv_modes_tieable_p (machine_mode mode1, machine_mode mode2)
 {
+  /* We don't allow different REG_CLASS modes tieable since it
+     will cause ICE in register allocation (RA).
+     E.g. V2SI and DI are not tieable.  */
+  if (riscv_v_ext_mode_p (mode1) && !riscv_v_ext_mode_p (mode2))
+    return false;
+  else if (riscv_v_ext_mode_p (mode2) && !riscv_v_ext_mode_p (mode1))
+    return false;
   return (mode1 == mode2
 	  || !(GET_MODE_CLASS (mode1) == MODE_FLOAT
 	       && GET_MODE_CLASS (mode2) == MODE_FLOAT));
diff --git a/gcc/testsuite/g++.target/riscv/rvv/base/pr111296.C b/gcc/testsuite/g++.target/riscv/rvv/base/pr111296.C
new file mode 100644
index 00000000000..6eb14fd83a8
--- /dev/null
+++ b/gcc/testsuite/g++.target/riscv/rvv/base/pr111296.C
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-std=c++03 -march=rv64gcv -mabi=lp64d -Ofast -ftree-vectorize --param=riscv-autovec-preference=scalable" } */
+
+struct a
+{
+  int b;
+  int c;
+};
+int d;
+a
+e ()
+{
+  a f;
+  int g = d - 1, h = d / 2 - 1;
+  f.b = g;
+  f.c = h;
+  return f;
+}
-- 
2.36.3