[gcc r12-9732] Mark asm goto with outputs as volatile

[gcc r12-9732] Mark asm goto with outputs as volatile

[Andrew Pinski]

https://gcc.gnu.org/g:ee3bb7cb5d2ecfc64adcfd61afb390e72cc08661

commit r12-9732-gee3bb7cb5d2ecfc64adcfd61afb390e72cc08661
Author: Andrew Pinski <apinski@marvell.com>
Date:   Mon Jun 26 17:14:06 2023 -0700

    Mark asm goto with outputs as volatile
    
    The manual references asm goto as being implicitly volatile already
    and that was done when asm goto could not have outputs. When outputs
    were added to `asm goto`, only asm goto without outputs were still being
    marked as volatile. Now some parts of GCC decide, removing the `asm goto`
    is ok if the output is not used, though not updating the CFG (this happens
    on both the RTL level and the gimple level). Since the biggest user of `asm goto`
    is the Linux kernel and they expect them to be volatile (they use them to
    copy to/from userspace), we should just mark the inline-asm as volatile.
    
    OK? Bootstrapped and tested on x86_64-linux-gnu.
    
            PR middle-end/110420
            PR middle-end/103979
            PR middle-end/98619
    
    gcc/ChangeLog:
    
            * gimplify.cc (gimplify_asm_expr): Mark asm with labels as volatile.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.c-torture/compile/asmgoto-6.c: New test.
    
    (cherry picked from commit 478840a2ca491fbff44371caee4983d1e7b7b7cf)

Diff:
---
 gcc/gimplify.cc                                 |  7 ++++++-
 gcc/testsuite/gcc.c-torture/compile/asmgoto-6.c | 26 +++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index a551c574a2d..947fe570e1e 100644
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -6847,7 +6847,12 @@ gimplify_asm_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
       stmt = gimple_build_asm_vec (TREE_STRING_POINTER (ASM_STRING (expr)),
 				   inputs, outputs, clobbers, labels);
 
-      gimple_asm_set_volatile (stmt, ASM_VOLATILE_P (expr) || noutputs == 0);
+      /* asm is volatile if it was marked by the user as volatile or
+	 there are no outputs or this is an asm goto.  */
+      gimple_asm_set_volatile (stmt,
+			       ASM_VOLATILE_P (expr)
+			       || noutputs == 0
+			       || labels);
       gimple_asm_set_input (stmt, ASM_INPUT_P (expr));
       gimple_asm_set_inline (stmt, ASM_INLINE_P (expr));
 
diff --git a/gcc/testsuite/gcc.c-torture/compile/asmgoto-6.c b/gcc/testsuite/gcc.c-torture/compile/asmgoto-6.c
new file mode 100644
index 00000000000..0652bd4e4e1
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/asmgoto-6.c
@@ -0,0 +1,26 @@
+
+/* { dg-do compile } */
+/* PR middle-end/110420 */
+/* PR middle-end/103979 */
+/* PR middle-end/98619 */
+/* Test that the middle-end does not remove the asm goto
+   with an output. */
+
+static int t;
+void g(void);
+
+void f(void)
+{
+  int  __gu_val;
+  asm goto("#my asm "
+     : "=&r"(__gu_val)
+     :
+     :
+     : Efault);
+  t = __gu_val;
+  g();
+Efault:
+}
+
+/* Make sure "my asm " is still in the assembly. */
+/* { dg-final { scan-assembler "my asm " } } */