[gcc r14-3744] RISC-V: Fix incorrect mode tieable which cause ICE in RA[PR111296]

[gcc r14-3744] RISC-V: Fix incorrect mode tieable which cause ICE in RA[PR111296]

[Pan Li]

https://gcc.gnu.org/g:6b96de22d6bcadb45530c1898b264e4738afa4fd

commit r14-3744-g6b96de22d6bcadb45530c1898b264e4738afa4fd
Author: Juzhe-Zhong <juzhe.zhong@rivai.ai>
Date:   Wed Sep 6 22:28:03 2023 +0800

    RISC-V: Fix incorrect mode tieable which cause ICE in RA[PR111296]
    
    This patch fix incorrect mode tieable between DI and V2SI which cause ICE
    in RA.
    
    gcc/ChangeLog:
    
            PR target/111296
            * config/riscv/riscv.cc (riscv_modes_tieable_p): Fix incorrect mode
            tieable for RVV modes.
    
    gcc/testsuite/ChangeLog:
    
            PR target/111296
            * g++.target/riscv/rvv/base/pr111296.C: New test.

Diff:
---
 gcc/config/riscv/riscv.cc                          |  5 +++++
 gcc/testsuite/g++.target/riscv/rvv/base/pr111296.C | 18 ++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 228515acc1f0..a3d3389e7e25 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -7648,6 +7648,11 @@ 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;
   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 000000000000..6eb14fd83a80
--- /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;
+}