[PATCH] RISC-V: Add tests for constraints "i" and "s"

[Fangrui Song]

The constraints "i" and "s" can be used with a symbol that binds
externally, e.g.
```
namespace ns { extern int var, a[4]; }
void foo() {
  asm(".pushsection .xxx,\"aw\"; .dc.a %0; .popsection" :: "s"(&ns::var));
  asm(".reloc ., BFD_RELOC_NONE, %0" :: "s"(&ns::a[3]));
}
```

gcc/testsuite/ChangeLog:

        * gcc.target/riscv/asm-raw-symbol.c: New test.
---
 gcc/doc/md.texi                                 |  2 +-
 gcc/testsuite/gcc.target/riscv/asm-raw-symbol.c | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/riscv/asm-raw-symbol.c

diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index b0c61925120..c75e5bf259d 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -1947,7 +1947,7 @@ Integer constant that is valid as an immediate operand in 
a 64-bit @code{MOV}
 pseudo instruction
 
 @item S
-An absolute symbolic address or a label reference
+A symbolic reference or label reference.
 
 @item Y
 Floating point constant zero
diff --git a/gcc/testsuite/gcc.target/riscv/asm-raw-symbol.c 
b/gcc/testsuite/gcc.target/riscv/asm-raw-symbol.c
new file mode 100644
index 00000000000..28305a8b1f0
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/asm-raw-symbol.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-fpic" } */
+
+extern int var, arr[2][2];
+
+void
+test (void)
+{
+  __asm__ ("@ %0" : : "i"(&var));
+  __asm__ ("@ %0 %1 %2" : : "s"(&var), "s"(&arr[1][1]), "s"(test));
+}
+
+/* { dg-final { scan-assembler "@ var arr\\+12 test" } } */
+/* { dg-final { scan-assembler "@ var" } } */
-- 
2.43.0.687.g38aa6559b0-goog