RISC-V: Add riscv_vector_cc function attribute

From: xuli <xuli1@eswincomputing.com>

Standard vector calling convention variant will only enabled when function
has vector argument or returning value by default, however user may also
want to invoke function without that during a vectorized loop at some situation,
but it will cause a huge performance penalty due to vector register store/restore.

So user can declare function with this riscv_vector_cc attribute like below, that could enforce
function will use standard vector calling convention variant.

void foo() __attribute__((riscv_vector_cc));
[[riscv::vector_cc]] void foo(); // For C++11 and C23

For more details please reference the below link.
https://github.com/riscv-non-isa/riscv-c-api-doc/pull/67

gcc/ChangeLog:

	* config/riscv/riscv.cc (TARGET_GNU_ATTRIBUTES): Add riscv_vector_cc
	attribute to riscv_attribute_table.
	(riscv_vector_cc_function_p): Return true if FUNC is a riscv_vector_cc function.
	(riscv_fntype_abi): Add riscv_vector_cc attribute check.
	* doc/extend.texi: Add riscv_vector_cc attribute description.

gcc/testsuite/ChangeLog:

	* g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C: New test.
	* gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c: New test.
	* gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c: New test.
---
 gcc/config/riscv/riscv.cc                     |  55 ++++++--
 gcc/doc/extend.texi                           |  12 ++
 .../base/attribute-riscv_vector_cc-error.C    |  22 ++++
 .../attribute-riscv_vector_cc-callee-saved.c  | 117 ++++++++++++++++++
 .../base/attribute-riscv_vector_cc-error.c    |  11 ++
 5 files changed, 209 insertions(+), 8 deletions(-)
 create mode 100644 gcc/testsuite/g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c

Thanks for supporting this.
I'd rather leave this patch review to kito's since it's kito's proposal.



juzhe.zhong@rivai.ai
 
From: Li Xu
Date: 2024-02-27 09:17
To: gcc-patches
CC: kito.cheng; palmer; juzhe.zhong; zhengyu; xuli
Subject: [PATCH] RISC-V: Add riscv_vector_cc function attribute
From: xuli <xuli1@eswincomputing.com>
 
Standard vector calling convention variant will only enabled when function
has vector argument or returning value by default, however user may also
want to invoke function without that during a vectorized loop at some situation,
but it will cause a huge performance penalty due to vector register store/restore.
 
So user can declare function with this riscv_vector_cc attribute like below, that could enforce
function will use standard vector calling convention variant.
 
void foo() __attribute__((riscv_vector_cc));
[[riscv::vector_cc]] void foo(); // For C++11 and C23
 
For more details please reference the below link.
https://github.com/riscv-non-isa/riscv-c-api-doc/pull/67
 
gcc/ChangeLog:
 
* config/riscv/riscv.cc (TARGET_GNU_ATTRIBUTES): Add riscv_vector_cc
attribute to riscv_attribute_table.
(riscv_vector_cc_function_p): Return true if FUNC is a riscv_vector_cc function.
(riscv_fntype_abi): Add riscv_vector_cc attribute check.
* doc/extend.texi: Add riscv_vector_cc attribute description.
 
gcc/testsuite/ChangeLog:
 
* g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C: New test.
* gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c: New test.
* gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c: New test.
---
gcc/config/riscv/riscv.cc                     |  55 ++++++--
gcc/doc/extend.texi                           |  12 ++
.../base/attribute-riscv_vector_cc-error.C    |  22 ++++
.../attribute-riscv_vector_cc-callee-saved.c  | 117 ++++++++++++++++++
.../base/attribute-riscv_vector_cc-error.c    |  11 ++
5 files changed, 209 insertions(+), 8 deletions(-)
create mode 100644 gcc/testsuite/g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C
create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c
create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c
 
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 4100abc9dd1..7f37f231796 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -537,24 +537,52 @@ static tree riscv_handle_fndecl_attribute (tree *, tree, tree, int, bool *);
static tree riscv_handle_type_attribute (tree *, tree, tree, int, bool *);
/* Defining target-specific uses of __attribute__.  */
-TARGET_GNU_ATTRIBUTES (riscv_attribute_table,
+static const attribute_spec riscv_gnu_attributes[] =
{
   /* Syntax: { name, min_len, max_len, decl_required, type_required,
       function_type_required, affects_type_identity, handler,
       exclude } */
   /* The attribute telling no prologue/epilogue.  */
-  { "naked", 0,  0, true, false, false, false,
-    riscv_handle_fndecl_attribute, NULL },
+  {"naked", 0, 0, true, false, false, false, riscv_handle_fndecl_attribute,
+   NULL},
   /* This attribute generates prologue/epilogue for interrupt handlers.  */
-  { "interrupt", 0, 1, false, true, true, false,
-    riscv_handle_type_attribute, NULL },
+  {"interrupt", 0, 1, false, true, true, false, riscv_handle_type_attribute,
+   NULL},
   /* The following two are used for the built-in properties of the Vector type
      and are not used externally */
   {"RVV sizeless type", 4, 4, false, true, false, true, NULL, NULL},
-  {"RVV type", 0, 0, false, true, false, true, NULL, NULL}
-});
+  {"RVV type", 0, 0, false, true, false, true, NULL, NULL},
+  /* This attribute is used to declare a function, forcing it to use the
+    standard vector calling convention variant. Syntax:
+    __attribute__((riscv_vector_cc)). */
+  {"riscv_vector_cc", 0, 0, false, true, true, true, NULL, NULL}
+};
+
+static const scoped_attribute_specs riscv_gnu_attribute_table  =
+{
+  "gnu", {riscv_gnu_attributes}
+};
+
+static const attribute_spec riscv_attributes[] =
+{
+  /* This attribute is used to declare a function, forcing it to use the
+     standard vector calling convention variant. Syntax:
+     [[riscv::vector_cc]]. */
+  {"vector_cc", 0, 0, false, true, true, true, NULL, NULL}
+};
+
+static const scoped_attribute_specs riscv_nongnu_attribute_table =
+{
+  "riscv", {riscv_attributes}
+};
+
+static const scoped_attribute_specs *const riscv_attribute_table[] =
+{
+  &riscv_gnu_attribute_table,
+  &riscv_nongnu_attribute_table
+};
/* Order for the CLOBBERs/USEs of gpr_save.  */
static const unsigned gpr_save_reg_order[] = {
@@ -5425,6 +5453,16 @@ riscv_arguments_is_vector_type_p (const_tree fntype)
   return false;
}
+/* Return true if FUNC is a riscv_vector_cc function.
+   For more details please reference the below link.
+   https://github.com/riscv-non-isa/riscv-c-api-doc/pull/67 */
+static bool
+riscv_vector_cc_function_p (const_tree fntype)
+{
+  return lookup_attribute ("vector_cc", TYPE_ATTRIBUTES (fntype)) != NULL_TREE
+ || lookup_attribute ("riscv_vector_cc", TYPE_ATTRIBUTES (fntype)) != NULL_TREE;
+}
+
/* Implement TARGET_FNTYPE_ABI.  */
static const predefined_function_abi &
@@ -5434,7 +5472,8 @@ riscv_fntype_abi (const_tree fntype)
      reference the below link.
      https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/389  */
   if (riscv_return_value_is_vector_type_p (fntype)
-   || riscv_arguments_is_vector_type_p (fntype))
+   || riscv_arguments_is_vector_type_p (fntype)
+   || riscv_vector_cc_function_p (fntype))
     return riscv_v_abi ();
   return default_function_abi;
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 2135dfde9c8..afe486ba47b 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -6314,6 +6314,18 @@ Permissible values for this parameter are @code{user}, @code{supervisor},
and @code{machine}.  If there is no parameter, then it defaults to
@code{machine}.
+@cindex @code{riscv_vector_cc} function attribute, RISC-V
+@item riscv_vector_cc
+Use this attribute to force the function to use the vector calling
+convention variant.
+For more information on riscv_vector_cc, please see
+@uref{https://github.com/riscv-non-isa/riscv-c-api-doc/pull/67}
+
+@smallexample
+void foo() __attribute__((riscv_vector_cc));
+[[riscv::vector_cc]] void foo(); // For C++11 and C23
+@end smallexample
+
@end table
The following target-specific function attributes are available for the
diff --git a/gcc/testsuite/g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C b/gcc/testsuite/g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C
new file mode 100644
index 00000000000..7a547b5e7ff
--- /dev/null
+++ b/gcc/testsuite/g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O1" } */
+
+
+[[riscv::vector_cc]] void foo();// For C++11 and C23
+
+[[riscv::vector_cc]] int var; /* { dg-warning "'vector_cc' attribute only applies to function types" } */
+
+void __attribute__((riscv_vector_cc)) func();
+void __attribute__((riscv_vector_cc(1))) func_invalid(); /* { dg-error "wrong number of arguments specified for 'riscv_vector_cc' attribute" } */
+
+void test_no_attribute(int);
+void  __attribute__((riscv_vector_cc)) test_no_attribute(int x) { }
+
+class test_cc {
+   __attribute__((riscv_vector_cc)) void member_func();
+};
+
+void test_lambda() {
+   __attribute__((riscv_vector_cc)) auto lambda = []() { /* { dg-warning "'riscv_vector_cc' attribute only applies to function types" } */
+  };
+}
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c b/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c
new file mode 100644
index 00000000000..7db9d874bcd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c
@@ -0,0 +1,117 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O1" } */
+/* { dg-final { check-function-bodies "**" "" } } */
+
+#include <stdint.h>
+
+void __attribute__((riscv_vector_cc)) bar1 (int a);
+void bar2 ();
+
+/*
+** foo1:
+**   addi\tsp,sp,-16
+**   sd\tra,8\(sp\)
+**   call\tbar1
+**   ld\tra,8\(sp\)
+**   addi\tsp,sp,16
+**   jr\tra
+*/
+void __attribute__((riscv_vector_cc))
+foo1 (int a)
+{
+  bar1 (a);
+}
+
+/*
+**  foo2:
+**    addi\tsp,sp,-16
+**    sd\tra,8\(sp\)
+**    csrr\tt0,vlenb
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv1,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv2,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv3,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv4,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv5,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv6,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv7,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv24,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv25,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv26,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv27,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv28,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv29,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv30,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv31,0\(sp\)
+**    call\tbar2
+**    csrr\tt0,vlenb
+**    vl1re64\.v\tv31,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv30,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv29,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv28,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv27,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv26,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv25,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv24,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv7,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv6,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv5,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv4,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv3,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv2,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv1,0\(sp\)
+**    add\tsp,sp,t0
+**    ld\tra,8\(sp\)
+**    addi\tsp,sp,16
+**    jr\tra
+*/
+void __attribute__((riscv_vector_cc))
+foo2 (int a)
+{
+  int8_t data[1024];
+  bar2 ();
+}
+
+/*
+** foo3:
+**   addi\tsp,sp,-16
+**   sd\tra,8\(sp\)
+**   lw\ta0,0\(a0\)
+**   call\tbar1
+**   ld\tra,8\(sp\)
+**   addi\tsp,sp,16
+**   jr\tra
+*/
+void
+foo3 (int *a)
+{
+  bar1 (*a);
+}
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c b/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c
new file mode 100644
index 00000000000..ceb5e5bf6dd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O1" } */
+
+__attribute__((riscv_vector_cc)) int var; /* { dg-warning "'riscv_vector_cc' attribute only applies to function types" } */
+[[riscv::vector_cc]] int var1; /* { dg-warning "'vector_cc' attribute only applies to function types" } */
+
+void __attribute__((riscv_vector_cc)) func();
+void __attribute__((riscv_vector_cc(1))) func_invalid(); /* { dg-error "wrong number of arguments specified for 'riscv_vector_cc' attribute" } */
+
+void test_no_attribute(int);
+void __attribute__((riscv_vector_cc)) test_no_attribute(int x) { }

Ping.



xuli1@eswincomputing.com
 
From: Li Xu
Date: 2024-02-27 09:17
To: gcc-patches
CC: kito.cheng; palmer; juzhe.zhong; zhengyu; xuli
Subject: [PATCH] RISC-V: Add riscv_vector_cc function attribute
From: xuli <xuli1@eswincomputing.com>
 
Standard vector calling convention variant will only enabled when function
has vector argument or returning value by default, however user may also
want to invoke function without that during a vectorized loop at some situation,
but it will cause a huge performance penalty due to vector register store/restore.
 
So user can declare function with this riscv_vector_cc attribute like below, that could enforce
function will use standard vector calling convention variant.
 
void foo() __attribute__((riscv_vector_cc));
[[riscv::vector_cc]] void foo(); // For C++11 and C23
 
For more details please reference the below link.
https://github.com/riscv-non-isa/riscv-c-api-doc/pull/67
 
gcc/ChangeLog:
 
* config/riscv/riscv.cc (TARGET_GNU_ATTRIBUTES): Add riscv_vector_cc
attribute to riscv_attribute_table.
(riscv_vector_cc_function_p): Return true if FUNC is a riscv_vector_cc function.
(riscv_fntype_abi): Add riscv_vector_cc attribute check.
* doc/extend.texi: Add riscv_vector_cc attribute description.
 
gcc/testsuite/ChangeLog:
 
* g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C: New test.
* gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c: New test.
* gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c: New test.
---
gcc/config/riscv/riscv.cc                     |  55 ++++++--
gcc/doc/extend.texi                           |  12 ++
.../base/attribute-riscv_vector_cc-error.C    |  22 ++++
.../attribute-riscv_vector_cc-callee-saved.c  | 117 ++++++++++++++++++
.../base/attribute-riscv_vector_cc-error.c    |  11 ++
5 files changed, 209 insertions(+), 8 deletions(-)
create mode 100644 gcc/testsuite/g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C
create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c
create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c
 
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 4100abc9dd1..7f37f231796 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -537,24 +537,52 @@ static tree riscv_handle_fndecl_attribute (tree *, tree, tree, int, bool *);
static tree riscv_handle_type_attribute (tree *, tree, tree, int, bool *);
/* Defining target-specific uses of __attribute__.  */
-TARGET_GNU_ATTRIBUTES (riscv_attribute_table,
+static const attribute_spec riscv_gnu_attributes[] =
{
   /* Syntax: { name, min_len, max_len, decl_required, type_required,
       function_type_required, affects_type_identity, handler,
       exclude } */
   /* The attribute telling no prologue/epilogue.  */
-  { "naked", 0,  0, true, false, false, false,
-    riscv_handle_fndecl_attribute, NULL },
+  {"naked", 0, 0, true, false, false, false, riscv_handle_fndecl_attribute,
+   NULL},
   /* This attribute generates prologue/epilogue for interrupt handlers.  */
-  { "interrupt", 0, 1, false, true, true, false,
-    riscv_handle_type_attribute, NULL },
+  {"interrupt", 0, 1, false, true, true, false, riscv_handle_type_attribute,
+   NULL},
   /* The following two are used for the built-in properties of the Vector type
      and are not used externally */
   {"RVV sizeless type", 4, 4, false, true, false, true, NULL, NULL},
-  {"RVV type", 0, 0, false, true, false, true, NULL, NULL}
-});
+  {"RVV type", 0, 0, false, true, false, true, NULL, NULL},
+  /* This attribute is used to declare a function, forcing it to use the
+    standard vector calling convention variant. Syntax:
+    __attribute__((riscv_vector_cc)). */
+  {"riscv_vector_cc", 0, 0, false, true, true, true, NULL, NULL}
+};
+
+static const scoped_attribute_specs riscv_gnu_attribute_table  =
+{
+  "gnu", {riscv_gnu_attributes}
+};
+
+static const attribute_spec riscv_attributes[] =
+{
+  /* This attribute is used to declare a function, forcing it to use the
+     standard vector calling convention variant. Syntax:
+     [[riscv::vector_cc]]. */
+  {"vector_cc", 0, 0, false, true, true, true, NULL, NULL}
+};
+
+static const scoped_attribute_specs riscv_nongnu_attribute_table =
+{
+  "riscv", {riscv_attributes}
+};
+
+static const scoped_attribute_specs *const riscv_attribute_table[] =
+{
+  &riscv_gnu_attribute_table,
+  &riscv_nongnu_attribute_table
+};
/* Order for the CLOBBERs/USEs of gpr_save.  */
static const unsigned gpr_save_reg_order[] = {
@@ -5425,6 +5453,16 @@ riscv_arguments_is_vector_type_p (const_tree fntype)
   return false;
}
+/* Return true if FUNC is a riscv_vector_cc function.
+   For more details please reference the below link.
+   https://github.com/riscv-non-isa/riscv-c-api-doc/pull/67 */
+static bool
+riscv_vector_cc_function_p (const_tree fntype)
+{
+  return lookup_attribute ("vector_cc", TYPE_ATTRIBUTES (fntype)) != NULL_TREE
+ || lookup_attribute ("riscv_vector_cc", TYPE_ATTRIBUTES (fntype)) != NULL_TREE;
+}
+
/* Implement TARGET_FNTYPE_ABI.  */
static const predefined_function_abi &
@@ -5434,7 +5472,8 @@ riscv_fntype_abi (const_tree fntype)
      reference the below link.
      https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/389  */
   if (riscv_return_value_is_vector_type_p (fntype)
-   || riscv_arguments_is_vector_type_p (fntype))
+   || riscv_arguments_is_vector_type_p (fntype)
+   || riscv_vector_cc_function_p (fntype))
     return riscv_v_abi ();
   return default_function_abi;
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 2135dfde9c8..afe486ba47b 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -6314,6 +6314,18 @@ Permissible values for this parameter are @code{user}, @code{supervisor},
and @code{machine}.  If there is no parameter, then it defaults to
@code{machine}.
+@cindex @code{riscv_vector_cc} function attribute, RISC-V
+@item riscv_vector_cc
+Use this attribute to force the function to use the vector calling
+convention variant.
+For more information on riscv_vector_cc, please see
+@uref{https://github.com/riscv-non-isa/riscv-c-api-doc/pull/67}
+
+@smallexample
+void foo() __attribute__((riscv_vector_cc));
+[[riscv::vector_cc]] void foo(); // For C++11 and C23
+@end smallexample
+
@end table
The following target-specific function attributes are available for the
diff --git a/gcc/testsuite/g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C b/gcc/testsuite/g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C
new file mode 100644
index 00000000000..7a547b5e7ff
--- /dev/null
+++ b/gcc/testsuite/g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O1" } */
+
+
+[[riscv::vector_cc]] void foo();// For C++11 and C23
+
+[[riscv::vector_cc]] int var; /* { dg-warning "'vector_cc' attribute only applies to function types" } */
+
+void __attribute__((riscv_vector_cc)) func();
+void __attribute__((riscv_vector_cc(1))) func_invalid(); /* { dg-error "wrong number of arguments specified for 'riscv_vector_cc' attribute" } */
+
+void test_no_attribute(int);
+void  __attribute__((riscv_vector_cc)) test_no_attribute(int x) { }
+
+class test_cc {
+   __attribute__((riscv_vector_cc)) void member_func();
+};
+
+void test_lambda() {
+   __attribute__((riscv_vector_cc)) auto lambda = []() { /* { dg-warning "'riscv_vector_cc' attribute only applies to function types" } */
+  };
+}
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c b/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c
new file mode 100644
index 00000000000..7db9d874bcd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c
@@ -0,0 +1,117 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O1" } */
+/* { dg-final { check-function-bodies "**" "" } } */
+
+#include <stdint.h>
+
+void __attribute__((riscv_vector_cc)) bar1 (int a);
+void bar2 ();
+
+/*
+** foo1:
+**   addi\tsp,sp,-16
+**   sd\tra,8\(sp\)
+**   call\tbar1
+**   ld\tra,8\(sp\)
+**   addi\tsp,sp,16
+**   jr\tra
+*/
+void __attribute__((riscv_vector_cc))
+foo1 (int a)
+{
+  bar1 (a);
+}
+
+/*
+**  foo2:
+**    addi\tsp,sp,-16
+**    sd\tra,8\(sp\)
+**    csrr\tt0,vlenb
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv1,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv2,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv3,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv4,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv5,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv6,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv7,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv24,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv25,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv26,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv27,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv28,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv29,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv30,0\(sp\)
+**    sub\tsp,sp,t0
+**    vs1r\.v\tv31,0\(sp\)
+**    call\tbar2
+**    csrr\tt0,vlenb
+**    vl1re64\.v\tv31,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv30,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv29,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv28,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv27,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv26,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv25,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv24,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv7,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv6,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv5,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv4,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv3,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv2,0\(sp\)
+**    add\tsp,sp,t0
+**    vl1re64\.v\tv1,0\(sp\)
+**    add\tsp,sp,t0
+**    ld\tra,8\(sp\)
+**    addi\tsp,sp,16
+**    jr\tra
+*/
+void __attribute__((riscv_vector_cc))
+foo2 (int a)
+{
+  int8_t data[1024];
+  bar2 ();
+}
+
+/*
+** foo3:
+**   addi\tsp,sp,-16
+**   sd\tra,8\(sp\)
+**   lw\ta0,0\(a0\)
+**   call\tbar1
+**   ld\tra,8\(sp\)
+**   addi\tsp,sp,16
+**   jr\tra
+*/
+void
+foo3 (int *a)
+{
+  bar1 (*a);
+}
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c b/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c
new file mode 100644
index 00000000000..ceb5e5bf6dd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O1" } */
+
+__attribute__((riscv_vector_cc)) int var; /* { dg-warning "'riscv_vector_cc' attribute only applies to function types" } */
+[[riscv::vector_cc]] int var1; /* { dg-warning "'vector_cc' attribute only applies to function types" } */
+
+void __attribute__((riscv_vector_cc)) func();
+void __attribute__((riscv_vector_cc(1))) func_invalid(); /* { dg-error "wrong number of arguments specified for 'riscv_vector_cc' attribute" } */
+
+void test_no_attribute(int);
+void __attribute__((riscv_vector_cc)) test_no_attribute(int x) { }

Thanks for your patch! this is generally in good shape, just a few
minor comments :)


> diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
> index 2135dfde9c8..afe486ba47b 100644
> --- a/gcc/doc/extend.texi
> +++ b/gcc/doc/extend.texi
> @@ -6314,6 +6314,18 @@ Permissible values for this parameter are @code{user}, @code{supervisor},
>  and @code{machine}.  If there is no parameter, then it defaults to
>  @code{machine}.
>
> +@cindex @code{riscv_vector_cc} function attribute, RISC-V
> +@item riscv_vector_cc
> +Use this attribute to force the function to use the vector calling
> +convention variant.
> +For more information on riscv_vector_cc, please see
> +@uref{https://github.com/riscv-non-isa/riscv-c-api-doc/pull/67}

Please remove above two line, I guess it's not good idea to reference
a pull request link here :P

> +
> +@smallexample
> +void foo() __attribute__((riscv_vector_cc));
> +[[riscv::vector_cc]] void foo(); // For C++11 and C23
> +@end smallexample
> +
>  @end table
>
>  The following target-specific function attributes are available for the

> diff --git a/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c b/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c
> new file mode 100644
> index 00000000000..7db9d874bcd
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c
> @@ -0,0 +1,117 @@
> +/* { dg-do compile } */
> +/* { dg-options "-march=rv64gcv -mabi=lp64d -O1" } */
> +/* { dg-final { check-function-bodies "**" "" } } */

I would like to prevent scanning the asm body if possible, since it
might cause problem when we improving code gen, so could you try to
scan .variant_cc\t<funcname> like
gcc/testsuite/gcc.target/aarch64/pcs_attribute-3.c?

Then we can also drop -O1 in the option :)

> +
> +#include <stdint.h>

Drop this.


> +void __attribute__((riscv_vector_cc))
> +foo2 (int a)
> +{
> +  int8_t data[1024];

Just char rather than int8_t, I would like to remove unnecessary
header including if possible :)