On 2024-01-11, Uros Bizjak wrote:
On Thu, Jan 11, 2024 at 4:44 AM Fangrui Song <mask...@google.com> wrote:
Printing the raw symbol is useful in inline asm (e.g. in C++ to get the
mangled name). Similar constraints are available in other targets (e.g.
"S" for aarch64/riscv, "Cs" for m68k).
There isn't a good way for x86 yet, e.g. "i" doesn't work for
PIC/-mcmodel=large. This patch adds "z".
Please use W-prefixed multi-letter constraint name.
Uros.
Sounds good. How about "Ws"?
(I've asked overse...@gcc.gnu.org whether I can get gcc access (I
already have binutils-gdb/glibc access), so that I can land approved
patches myself in the future)
From ad7bf3dce026bf226e22ab709c9326c611a4b745 Mon Sep 17 00:00:00 2001
From: Fangrui Song <mask...@google.com>
Date: Wed, 10 Jan 2024 18:49:45 -0800
Subject: [PATCH] i386: Add "Ws" constraint for symbolic address/label
reference [PR105576]
Printing the raw symbol is useful in inline asm (e.g. in C++ to get the
mangled name). Similar constraints are available in other targets (e.g.
"S" for aarch64/riscv, "Cs" for m68k).
There isn't a good way for x86 yet, e.g. "i" doesn't work for
PIC/-mcmodel=large. This patch adds "Ws". Here are possible use cases:
```
namespace ns { extern int var; }
asm (".pushsection .xxx,\"aw\"; .dc.a %0; .popsection" :: "S"(&var));
asm (".reloc ., BFD_RELOC_NONE, %0" :: "S"(&var));
```
gcc/ChangeLog:
PR target/105576
* config/i386/constraints.md: Define constraint "Ws".
* doc/md.texi: Document it.
gcc/testsuite/ChangeLog:
* gcc.target/i386/asm-raw-symbol.c: New testcase.
---
gcc/config/i386/constraints.md | 4 ++++
gcc/doc/md.texi | 4 ++++
gcc/testsuite/gcc.target/i386/asm-raw-symbol.c | 13 +++++++++++++
3 files changed, 21 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/i386/asm-raw-symbol.c
diff --git a/gcc/config/i386/constraints.md b/gcc/config/i386/constraints.md
index 0c6e662df25..280e4c8e36c 100644
--- a/gcc/config/i386/constraints.md
+++ b/gcc/config/i386/constraints.md
@@ -348,6 +348,10 @@ (define_constraint "Wf"
to double word size."
(match_operand 0 "x86_64_dwzext_immediate_operand"))
+(define_constraint "Ws"
+ "A symbolic reference or label reference."
+ (match_code "const,symbol_ref,label_ref"))
+
(define_constraint "Z"
"32-bit unsigned integer constant, or a symbolic reference known
to fit that range (for immediate operands in zero-extending x86-64
diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index 47a87d6ceec..b0c61925120 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -4275,6 +4275,10 @@ require non-@code{VOIDmode} immediate operands).
128-bit integer constant where both the high and low 64-bit word
satisfy the @code{e} constraint.
+@item Ws
+A symbolic reference or label reference.
+You can use the @code{%p} modifier to print the raw symbol.
+
@item Z
32-bit unsigned integer constant, or a symbolic reference known
to fit that range (for immediate operands in zero-extending x86-64
diff --git a/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c
b/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c
new file mode 100644
index 00000000000..b7854567dd9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+
+extern int var;
+
+void
+func (void)
+{
+ __asm__ ("@ %p0" : : "Ws" (func));
+ __asm__ ("@ %p0" : : "Ws" (&var + 1));
+}
+
+/* { dg-final { scan-assembler "@ func" } } */
+/* { dg-final { scan-assembler "@ var\\+4" } } */
--
2.43.0.275.g3460e3d667-goog
