On Fri, Mar 26, 2021 at 5:09 AM Richard Biener
<richard.guent...@gmail.com> wrote:
>
> On Fri, Mar 26, 2021 at 11:26 AM Jakub Jelinek <ja...@redhat.com> wrote:
> >
> > On Fri, Mar 26, 2021 at 11:13:21AM +0100, Richard Biener wrote:
> > > On Fri, Mar 26, 2021 at 9:34 AM Jakub Jelinek via Gcc-patches
> > > <gcc-patches@gcc.gnu.org> wrote:
> > > >
> > > > On Thu, Mar 25, 2021 at 11:36:37AM -0700, H.J. Lu via Gcc-patches wrote:
> > > > > How can we move forward with it? I'd like to resolve it in GCC 11.
> > > >
> > > > I think it is too late for GCC 11 for this.
> > > > Especially if the solution would be that we change the behavior of
> > > > existing
> > > > attribute, we would need enough time to test everything in the wild that
> > > > we don't break it badly,
> > >
> > > But isn't the suggested change only going to make programs we reject now
> > > with an error accepted or ICEing? Thus, no program that works right now
> > > should break.
> >
> > That is true, but even
> > accepts-invalid
> > and
> > ice-on-invalid-code
> > would be important regressions.
> > Changing the always_inline attribute behavior without at least avoiding
> > the first of those for our intrinsics would be bad, and we need to look what
> > people use always_inline in the wild for and what are their expectations.
> > And for the intrinsics we need something maintainable, we have > 5000
> > intrinsics on i386 alone, > 4000 on aarch64, > 7000 on arm, > 600 on rs6000,
> > > 100 on sparc, I bet most of them rely on the current behavior.
> > I think the world doesn't end if we do it for GCC 12 only, do it right for
> > everything we are aware of and have many months to figure out what impact it
> > will have on programs in the wild.
>
> As said, my opinion is that this fallout doesn't "exist" in the wild
> since it can
> only exist for code we reject right now which in my definition of
> "out in the wild" makes it not exist. I consider only code accepted by
> the compiler as valid "out in the wild" example.
>
> See also the behavior of always-inline with regard to the optimize attribute.
>
> So yes, a better solution would be nice but I can't see any since the
> underlying issue is known since a long time and thus the pragmatic
> solution is the best (IMHO), also from a QOI perspective. For intrinsics
> it also avoids differences with -O0 vs -O with what we accept and reject.
Here is a simple patch for GCC 11 by defining __rdtsc and __rdtscp
as macros. OK for master?
Thanks.
--
H.J.
From 84c0019ee2a7125daaad161bfbb98c3bf74ca48b Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.to...@gmail.com>
Date: Tue, 23 Mar 2021 20:04:58 -0700
Subject: [PATCH] x86: Define __rdtsc and __rdtscp as macros
Define __rdtsc and __rdtscp as macros for callers with general-regs-only
target attribute to avoid inline failure with always_inline attribute.
gcc/
PR target/99744
* config/i386/ia32intrin.h (__rdtsc): Defined as macro.
(__rdtscp): Likewise.
gcc/testsuite/
PR target/99744
* gcc.target/i386/pr99744-1.c: New test.
---
gcc/config/i386/ia32intrin.h | 14 ++-----------
gcc/testsuite/gcc.target/i386/pr99744-1.c | 25 +++++++++++++++++++++++
2 files changed, 27 insertions(+), 12 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/i386/pr99744-1.c
diff --git a/gcc/config/i386/ia32intrin.h b/gcc/config/i386/ia32intrin.h
index d336a51669a..591394076cc 100644
--- a/gcc/config/i386/ia32intrin.h
+++ b/gcc/config/i386/ia32intrin.h
@@ -107,22 +107,12 @@ __rdpmc (int __S)
#endif /* __iamcu__ */
/* rdtsc */
-extern __inline unsigned long long
-__attribute__((__gnu_inline__, __always_inline__, __artificial__))
-__rdtsc (void)
-{
- return __builtin_ia32_rdtsc ();
-}
+#define __rdtsc() __builtin_ia32_rdtsc ()
#ifndef __iamcu__
/* rdtscp */
-extern __inline unsigned long long
-__attribute__((__gnu_inline__, __always_inline__, __artificial__))
-__rdtscp (unsigned int *__A)
-{
- return __builtin_ia32_rdtscp (__A);
-}
+#define __rdtscp(a) __builtin_ia32_rdtscp (a)
#endif /* __iamcu__ */
diff --git a/gcc/testsuite/gcc.target/i386/pr99744-1.c b/gcc/testsuite/gcc.target/i386/pr99744-1.c
new file mode 100644
index 00000000000..a5a905c732a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr99744-1.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+#include <x86intrin.h>
+
+extern unsigned long long int curr_deadline;
+extern void bar (void);
+
+__attribute__ ((target("general-regs-only")))
+void
+foo1 (void)
+{
+ if (__rdtsc () < curr_deadline)
+ return;
+ bar ();
+}
+
+__attribute__ ((target("general-regs-only")))
+void
+foo2 (unsigned int *p)
+{
+ if (__rdtscp (p) < curr_deadline)
+ return;
+ bar ();
+}
--
2.30.2
