Re: [PATCH] x86-64: Use R10 for profiling large model

["H.J. Lu" <hjl.tools@gmail.com>]

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On Fri, Jan 8, 2021 at 1:24 AM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> > Since R10 is preserved when calling mcount, R10 can be used a scratch
> > register to call mcount in large model.
>
> Please mention that R10 can be used as a static chain registers and is
> preserved when calling mcount for nested functions.
>
> > gcc/
> >
> > PR target/98482
> > * config/i386/i386.c (x86_function_profiler): Use R10 to call
> > mcount in large model. Sorry for large model with PIC.
> >
> > gcc/testsuite/
> >
> > PR target/98482
> > * gcc.target/i386/pr98482-1.c: New test.
> > * gcc.target/i386/pr98482-1.c: Likewise.
>
> OK with comment fixes.
>
> Thanks,
> Uros.
>
> +    case CM_LARGE:
> +      /* NB: R10 can be used as a scratch register here since
> +        R10 is preserved when calling mcount.  */
>
> Also mention that R10 can be used as a static chain register and is
> preserved when calling mcount for nested functions.
>
> +      fprintf (file, "1:\tmovabsq\t$%s, %%r10\n\tcall\t*%%r10\n",
> +       mcount_name);
> +      break;

This is the patch I am checking in.

Thanks.

-- 
H.J.

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From 6ddaec60b84ccdfb11224440bfffa86112244d88 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 7 Jan 2021 14:27:49 -0800
Subject: [PATCH] x86-64: Use R10 for profiling large model

R10 is caller-saved.  Although it can be used as a static chain register,
it is preserved when calling mcount for nested functions.  Use R10 as a
scratch register to call mcount in large model.

gcc/

	PR target/98482
	* config/i386/i386.c (x86_function_profiler): Use R10 to call
	mcount in large model.  Sorry for large model with PIC.

gcc/testsuite/

	PR target/98482
	* gcc.target/i386/pr98482-1.c: New test.
	* gcc.target/i386/pr98482-1.c: Likewise.
---
 gcc/config/i386/i386.c                    | 26 +++++++++++++++++++++--
 gcc/testsuite/gcc.target/i386/pr98482-1.c |  9 ++++++++
 gcc/testsuite/gcc.target/i386/pr98482-2.c |  9 ++++++++
 3 files changed, 42 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr98482-1.c
 create mode 100644 gcc/testsuite/gcc.target/i386/pr98482-2.c

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index fad50e7e537..d3068462fcd 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -20794,8 +20794,30 @@ x86_function_profiler (FILE *file, int labelno ATTRIBUTE_UNUSED)
       fprintf (file, "\tleaq\t%sP%d(%%rip),%%r11\n", LPREFIX, labelno);
 #endif
 
-      if (!TARGET_PECOFF && flag_pic)
-	fprintf (file, "1:\tcall\t*%s@GOTPCREL(%%rip)\n", mcount_name);
+      if (!TARGET_PECOFF)
+	{
+	  switch (ix86_cmodel)
+	    {
+	    case CM_LARGE:
+	      /* NB: R10 is caller-saved.  Although it can be used as a
+		 static chain register, it is preserved when calling
+		 mcount for nested functions.  */
+	      fprintf (file, "1:\tmovabsq\t$%s, %%r10\n\tcall\t*%%r10\n",
+		       mcount_name);
+	      break;
+	    case CM_LARGE_PIC:
+	      sorry ("profiling %<-mcmodel=large%> with PIC is not supported");
+	      break;
+	    case CM_SMALL_PIC:
+	    case CM_MEDIUM_PIC:
+	      fprintf (file, "1:\tcall\t*%s@GOTPCREL(%%rip)\n",
+		       mcount_name);
+	      break;
+	    default:
+	      x86_print_call_or_nop (file, mcount_name);
+	      break;
+	    }
+	}
       else
 	x86_print_call_or_nop (file, mcount_name);
     }
diff --git a/gcc/testsuite/gcc.target/i386/pr98482-1.c b/gcc/testsuite/gcc.target/i386/pr98482-1.c
new file mode 100644
index 00000000000..72d5ccb269c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr98482-1.c
@@ -0,0 +1,9 @@
+/* { dg-do compile { target { *-*-linux* && { ! ia32 } } } } */
+/* { dg-require-effective-target mfentry } */
+/* { dg-options "-fprofile -mfentry -O2 -mcmodel=large" } */
+/* { dg-final { scan-assembler "movabsq\t\\\$__fentry__, %r10\n\tcall\t\\*%r10" } } */
+
+void
+func (void)
+{
+}
diff --git a/gcc/testsuite/gcc.target/i386/pr98482-2.c b/gcc/testsuite/gcc.target/i386/pr98482-2.c
new file mode 100644
index 00000000000..aed3ca4b6ff
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr98482-2.c
@@ -0,0 +1,9 @@
+/* { dg-do compile { target { *-*-linux* && { ! ia32 } } } } */
+/* { dg-require-effective-target mfentry } */
+/* { dg-require-effective-target fpic } */
+/* { dg-options "-fpic -fprofile -mfentry -O2 -mcmodel=large" } */
+
+void
+func (void)
+{
+} /* { dg-message "sorry, unimplemented: profiling '-mcmodel=large' with PIC is not supported" } */
-- 
2.29.2