Re: [PATCH] RISC-V: Handle vlenb correctly in unwinding

[<juzhe.zhong@rivai.ai>]

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LGTM



juzhe.zhong@rivai.ai
 
From: Kito Cheng
Date: 2023-02-12 19:33
To: gcc-patches; kito.cheng; jim.wilson.gcc; palmer; andrew; juzhe.zhong
CC: Kito Cheng
Subject: [PATCH] RISC-V: Handle vlenb correctly in unwinding
gcc/ChangeLog:
 
* config/riscv/riscv.h (RISCV_DWARF_VLENB): New.
(DWARF_FRAME_REGISTERS): New.
(DWARF_REG_TO_UNWIND_COLUMN): New.
 
libgcc/ChangeLog:
 
* config.host (riscv*-*-*): Add config/riscv/value-unwind.h.
* config/riscv/value-unwind.h: New.
---
gcc/config/riscv/riscv.h           |  7 ++++++
libgcc/config.host                 |  3 +++
libgcc/config/riscv/value-unwind.h | 39 ++++++++++++++++++++++++++++++
3 files changed, 49 insertions(+)
create mode 100644 libgcc/config/riscv/value-unwind.h
 
diff --git a/gcc/config/riscv/riscv.h b/gcc/config/riscv/riscv.h
index 120faf17c06..5bc7f2f467d 100644
--- a/gcc/config/riscv/riscv.h
+++ b/gcc/config/riscv/riscv.h
@@ -1088,4 +1088,11 @@ extern void riscv_remove_unneeded_save_restore_calls (void);
#define REGMODE_NATURAL_SIZE(MODE) riscv_regmode_natural_size (MODE)
+#define RISCV_DWARF_VLENB (4096 + 0xc22)
+
+#define DWARF_FRAME_REGISTERS (FIRST_PSEUDO_REGISTER + 1 /* VLENB */)
+
+#define DWARF_REG_TO_UNWIND_COLUMN(REGNO) \
+  ((REGNO == RISCV_DWARF_VLENB) ? (FIRST_PSEUDO_REGISTER + 1) : REGNO)
+
#endif /* ! GCC_RISCV_H */
diff --git a/libgcc/config.host b/libgcc/config.host
index 70d47e08e40..b9975de9023 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -1559,6 +1559,9 @@ aarch64*-*-*)
# ILP32 needs an extra header for unwinding
tm_file="${tm_file} aarch64/value-unwind.h"
;;
+riscv*-*-*)
+ tm_file="${tm_file} riscv/value-unwind.h"
+ ;;
esac
# Setup to build a shared libgcc for VxWorks when that was requested,
diff --git a/libgcc/config/riscv/value-unwind.h b/libgcc/config/riscv/value-unwind.h
new file mode 100644
index 00000000000..d7efdc14e6f
--- /dev/null
+++ b/libgcc/config/riscv/value-unwind.h
@@ -0,0 +1,39 @@
+/* Store register values as _Unwind_Word type in DWARF2 EH unwind context.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+   This file is part of GCC.
+
+   GCC is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3, or (at your
+   option) any later version.
+
+   GCC is distributed in the hope that it will be useful, but WITHOUT
+   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+   License for more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Return the value of the VLENB register.  This should only be
+   called if we know this is an vector extension enabled RISC-V host.  */
+static inline long
+riscv_vlenb (void)
+{
+  register long vlenb asm ("a0");
+  /* 0xc2202573 == csrr a0, 0xc22 */
+  asm (".insn 0xc2202573" : "=r"(vlenb));
+  return vlenb;
+}
+
+/* Lazily provide a value for VLENB, so that we don't try to execute RVV
+   instructions unless we know they're needed.  */
+#define DWARF_LAZY_REGISTER_VALUE(REGNO, VALUE) \
+  ((REGNO) == RISCV_DWARF_VLENB && ((*VALUE) = riscv_vlenb (), 1))
-- 
2.37.2