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* [PATCH v4] rs6000: Rework ELFv2 support for -fpatchable-function-entry* [PR99888]
@ 2022-08-25  5:50 Kewen.Lin
  2022-09-28  5:37 ` PING^1 " Kewen.Lin
  2022-09-28 15:22 ` Segher Boessenkool
  0 siblings, 2 replies; 4+ messages in thread
From: Kewen.Lin @ 2022-08-25  5:50 UTC (permalink / raw)
  To: GCC Patches; +Cc: Segher Boessenkool, David Edelsohn, AlanM

Hi,

As PR99888 and its related show, the current support for
-fpatchable-function-entry on powerpc ELFv2 doesn't work
well with global entry existence.  For example, with one
command line option -fpatchable-function-entry=3,2, it got
below w/o this patch:

  .LPFE1:
	  nop
	  nop
	  .type   foo, @function
  foo:
	  nop
  .LFB0:
	  .cfi_startproc
  .LCF0:
  0:      addis 2,12,.TOC.-.LCF0@ha
	  addi 2,2,.TOC.-.LCF0@l
	  .localentry     foo,.-foo

, the assembly is unexpected since the patched nops have
no effects when being entered from local entry.

This patch is to update the nops patched before and after
local entry, it looks like:

	  .type   foo, @function
  foo:
  .LFB0:
	  .cfi_startproc
  .LCF0:
  0:      addis 2,12,.TOC.-.LCF0@ha
	  addi 2,2,.TOC.-.LCF0@l
	  nop
	  nop
	  .localentry     foo,.-foo
	  nop

Bootstrapped and regtested on powerpc64-linux-gnu P7 & P8,
and powerpc64le-linux-gnu P9 & P10.

v4: Change the remaining NOP to nop and update documentation of option
    -fpatchable-function-entry for PowerPC ELFv2 ABI dual entry points
    as Segher suggested.

v3: https://gcc.gnu.org/pipermail/gcc-patches/2022-August/599925.html

v2: https://gcc.gnu.org/pipermail/gcc-patches/2022-August/599617.html

v1: https://gcc.gnu.org/pipermail/gcc-patches/2022-August/599461.html

Is it ok for trunk?

BR,
Kewen
----
	PR target/99888
	PR target/105649

gcc/ChangeLog:

	* doc/invoke.texi (option -fpatchable-function-entry): Adjust the
	documentation for PowerPC ELFv2 ABI dual entry points.
	* config/rs6000/rs6000-internal.h
	(rs6000_print_patchable_function_entry): New function declaration.
	* config/rs6000/rs6000-logue.cc (rs6000_output_function_prologue):
	Support patchable-function-entry by emitting nops before and after
	local entry for the function that needs global entry.
	* config/rs6000/rs6000.cc (rs6000_print_patchable_function_entry): Skip
	the function that needs global entry till global entry has been
	emitted.
	* config/rs6000/rs6000.h (struct machine_function): New bool member
	global_entry_emitted.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr99888-1.c: New test.
	* gcc.target/powerpc/pr99888-2.c: New test.
	* gcc.target/powerpc/pr99888-3.c: New test.
	* gcc.target/powerpc/pr99888-4.c: New test.
	* gcc.target/powerpc/pr99888-5.c: New test.
	* gcc.target/powerpc/pr99888-6.c: New test.
	* c-c++-common/patchable_function_entry-default.c: Adjust for
	powerpc_elfv2 to avoid compilation error.
---
 gcc/config/rs6000/rs6000-internal.h           |  5 +++
 gcc/config/rs6000/rs6000-logue.cc             | 32 ++++++++++++++
 gcc/config/rs6000/rs6000.cc                   | 10 ++++-
 gcc/config/rs6000/rs6000.h                    |  4 ++
 gcc/doc/invoke.texi                           |  8 +++-
 .../patchable_function_entry-default.c        |  3 ++
 gcc/testsuite/gcc.target/powerpc/pr99888-1.c  | 43 +++++++++++++++++++
 gcc/testsuite/gcc.target/powerpc/pr99888-2.c  | 43 +++++++++++++++++++
 gcc/testsuite/gcc.target/powerpc/pr99888-3.c  | 11 +++++
 gcc/testsuite/gcc.target/powerpc/pr99888-4.c  | 13 ++++++
 gcc/testsuite/gcc.target/powerpc/pr99888-5.c  | 13 ++++++
 gcc/testsuite/gcc.target/powerpc/pr99888-6.c  | 14 ++++++
 12 files changed, 195 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr99888-1.c
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr99888-2.c
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr99888-3.c
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr99888-4.c
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr99888-5.c
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr99888-6.c

diff --git a/gcc/config/rs6000/rs6000-internal.h b/gcc/config/rs6000/rs6000-internal.h
index 8ee8c987b81..d80c04b5ae5 100644
--- a/gcc/config/rs6000/rs6000-internal.h
+++ b/gcc/config/rs6000/rs6000-internal.h
@@ -183,10 +183,15 @@ extern tree rs6000_fold_builtin (tree fndecl ATTRIBUTE_UNUSED,
 			         tree *args ATTRIBUTE_UNUSED,
 			         bool ignore ATTRIBUTE_UNUSED);

+extern void rs6000_print_patchable_function_entry (FILE *,
+						   unsigned HOST_WIDE_INT,
+						   bool);
+
 extern bool rs6000_passes_float;
 extern bool rs6000_passes_long_double;
 extern bool rs6000_passes_vector;
 extern bool rs6000_returns_struct;
 extern bool cpu_builtin_p;

+
 #endif
diff --git a/gcc/config/rs6000/rs6000-logue.cc b/gcc/config/rs6000/rs6000-logue.cc
index 59fe1c8cb8b..51f55d1d527 100644
--- a/gcc/config/rs6000/rs6000-logue.cc
+++ b/gcc/config/rs6000/rs6000-logue.cc
@@ -4013,11 +4013,43 @@ rs6000_output_function_prologue (FILE *file)
 	  fprintf (file, "\tadd 2,2,12\n");
 	}

+      unsigned short patch_area_size = crtl->patch_area_size;
+      unsigned short patch_area_entry = crtl->patch_area_entry;
+      /* Need to emit the patching area.  */
+      if (patch_area_size > 0)
+	{
+	  cfun->machine->global_entry_emitted = true;
+	  /* As ELFv2 ABI shows, the allowable bytes between the global
+	     and local entry points are 0, 4, 8, 16, 32 and 64 when
+	     there is a local entry point.  Considering there are two
+	     non-prefixed instructions for global entry point prologue
+	     (8 bytes), the count for patchable nops before local entry
+	     point would be 2, 6 and 14.  It's possible to support those
+	     other counts of nops by not making a local entry point, but
+	     we don't have clear user cases for them, so leave them
+	     unsupported for now.  */
+	  if (patch_area_entry > 0)
+	    {
+	      if (patch_area_entry != 2
+		  && patch_area_entry != 6
+		  && patch_area_entry != 14)
+		error ("unsupported number of nops before function entry (%u)",
+		       patch_area_entry);
+	      rs6000_print_patchable_function_entry (file, patch_area_entry,
+						     true);
+	      patch_area_size -= patch_area_entry;
+	    }
+	}
+
       fputs ("\t.localentry\t", file);
       assemble_name (file, name);
       fputs (",.-", file);
       assemble_name (file, name);
       fputs ("\n", file);
+      /* Emit the nops after local entry.  */
+      if (patch_area_size > 0)
+	rs6000_print_patchable_function_entry (file, patch_area_size,
+					       patch_area_entry == 0);
     }

   else if (rs6000_pcrel_p ())
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 777a06599c3..c79a0ee7a49 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -14898,8 +14898,14 @@ rs6000_print_patchable_function_entry (FILE *file,
   if (!(TARGET_64BIT && DEFAULT_ABI != ABI_ELFv2)
       && HAVE_GAS_SECTION_LINK_ORDER)
     flags |= SECTION_LINK_ORDER;
-  default_print_patchable_function_entry_1 (file, patch_area_size, record_p,
-					    flags);
+  bool global_entry_needed_p = rs6000_global_entry_point_prologue_needed_p ();
+  /* For a function which needs global entry point, we will emit the
+     patchable area before and after local entry point under the control of
+     cfun->machine->global_entry_emitted, see the handling in function
+     rs6000_output_function_prologue.  */
+  if (!global_entry_needed_p || cfun->machine->global_entry_emitted)
+    default_print_patchable_function_entry_1 (file, patch_area_size, record_p,
+					      flags);
 }


 enum rtx_code
diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h
index ad9bf0f7358..c352421e87c 100644
--- a/gcc/config/rs6000/rs6000.h
+++ b/gcc/config/rs6000/rs6000.h
@@ -2439,6 +2439,10 @@ typedef struct GTY(()) machine_function
   bool lr_is_wrapped_separately;
   bool toc_is_wrapped_separately;
   bool mma_return_type_error;
+  /* Indicate global entry is emitted, only useful when the function requires
+     global entry.  It helps to control the patchable area before and after
+     local entry.  */
+  bool global_entry_emitted;
 } machine_function;
 #endif

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index b7c75028789..c98f5ceb0b9 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -16717,9 +16717,13 @@ the area size or to remove it completely on a single function.
 If @code{N=0}, no pad location is recorded.

 The NOP instructions are inserted at---and maybe before, depending on
-@var{M}---the function entry address, even before the prologue.
+@var{M}---the function entry address, even before the prologue.  On
+PowerPC with the ELFv2 ABI, for one function with dual entry points,
+the local entry point is taken as the function entry for generation.

-The maximum value of @var{N} and @var{M} is 65535.
+The maximum value of @var{N} and @var{M} is 65535.  On PowerPC with the
+ELFv2 ABI, for one function with dual entry points, the supported values
+for @var{M} are 0, 2, 6 and 14.
 @end table


diff --git a/gcc/testsuite/c-c++-common/patchable_function_entry-default.c b/gcc/testsuite/c-c++-common/patchable_function_entry-default.c
index 7036f7bfbea..a501efccb19 100644
--- a/gcc/testsuite/c-c++-common/patchable_function_entry-default.c
+++ b/gcc/testsuite/c-c++-common/patchable_function_entry-default.c
@@ -1,6 +1,9 @@
 /* { dg-do compile { target { ! { nvptx*-*-* visium-*-* } } } } */
 /* { dg-options "-O2 -fpatchable-function-entry=3,1" } */
 /* { dg-additional-options "-fno-pie" { target sparc*-*-* } } */
+/* See PR99888, one single preceding nop isn't allowed on powerpc_elfv2,
+   so overriding with two preceding nops to make it pass there.  */
+/* { dg-additional-options "-fpatchable-function-entry=3,2" { target powerpc_elfv2 } } */
 /* { dg-final { scan-assembler-times "nop|NOP|SWYM" 3 { target { ! { alpha*-*-* } } } } } */
 /* { dg-final { scan-assembler-times "bis" 3 { target alpha*-*-* } } } */

diff --git a/gcc/testsuite/gcc.target/powerpc/pr99888-1.c b/gcc/testsuite/gcc.target/powerpc/pr99888-1.c
new file mode 100644
index 00000000000..9370b4e7438
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr99888-1.c
@@ -0,0 +1,43 @@
+/* Verify no errors for different nops after local entry on ELFv2.  */
+
+extern int a;
+
+__attribute__ ((noipa, patchable_function_entry (1, 0)))
+int test1 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (2, 0)))
+int test2 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (3, 0)))
+int test3 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (4, 0)))
+int test4 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (5, 0)))
+int test5 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (6, 0)))
+int test6 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (7, 0)))
+int test7 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (8, 0)))
+int test8 (int b) {
+  return a + b;
+}
diff --git a/gcc/testsuite/gcc.target/powerpc/pr99888-2.c b/gcc/testsuite/gcc.target/powerpc/pr99888-2.c
new file mode 100644
index 00000000000..45061712602
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr99888-2.c
@@ -0,0 +1,43 @@
+/* Verify no errors for 2, 6 and 14 nops before local entry on ELFv2.  */
+
+extern int a;
+
+__attribute__ ((noipa, patchable_function_entry (2, 2)))
+int test1 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (4, 2)))
+int test2 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (6, 6)))
+int test3 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (8, 6)))
+int test4 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (16, 6)))
+int test5 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (14, 14)))
+int test6 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (28, 14)))
+int test7 (int b) {
+  return a + b;
+}
+
+__attribute__ ((noipa, patchable_function_entry (64, 14)))
+int test8 (int b) {
+  return a + b;
+}
diff --git a/gcc/testsuite/gcc.target/powerpc/pr99888-3.c b/gcc/testsuite/gcc.target/powerpc/pr99888-3.c
new file mode 100644
index 00000000000..4531ae32036
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr99888-3.c
@@ -0,0 +1,11 @@
+/* { dg-options "-fpatchable-function-entry=1" } */
+
+/* Verify no errors on ELFv2, using command line option instead of
+   function attribute.  */
+
+extern int a;
+
+int test (int b) {
+  return a + b;
+}
+
diff --git a/gcc/testsuite/gcc.target/powerpc/pr99888-4.c b/gcc/testsuite/gcc.target/powerpc/pr99888-4.c
new file mode 100644
index 00000000000..00a8d4d316e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr99888-4.c
@@ -0,0 +1,13 @@
+/* { dg-require-effective-target powerpc_elfv2 } */
+/* There is no global entry point prologue with pcrel.  */
+/* { dg-options "-mno-pcrel -fpatchable-function-entry=1,1" } */
+
+/* Verify one error emitted for unexpected 1 nop before local
+   entry.  */
+
+extern int a;
+
+int test (int b) {
+  return a + b;
+}
+/* { dg-error "unsupported number of nops before function entry \\(1\\)" "" { target *-*-* } .-1 } */
diff --git a/gcc/testsuite/gcc.target/powerpc/pr99888-5.c b/gcc/testsuite/gcc.target/powerpc/pr99888-5.c
new file mode 100644
index 00000000000..39d3b4465f1
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr99888-5.c
@@ -0,0 +1,13 @@
+/* { dg-require-effective-target powerpc_elfv2 } */
+/* There is no global entry point prologue with pcrel.  */
+/* { dg-options "-mno-pcrel -fpatchable-function-entry=7,3" } */
+
+/* Verify one error emitted for unexpected 3 nops before local
+   entry.  */
+
+extern int a;
+
+int test (int b) {
+  return a + b;
+}
+/* { dg-error "unsupported number of nops before function entry \\(3\\)" "" { target *-*-* } .-1 } */
diff --git a/gcc/testsuite/gcc.target/powerpc/pr99888-6.c b/gcc/testsuite/gcc.target/powerpc/pr99888-6.c
new file mode 100644
index 00000000000..c6c18dcc7ac
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr99888-6.c
@@ -0,0 +1,14 @@
+/* { dg-require-effective-target powerpc_elfv2 } */
+/* There is no global entry point prologue with pcrel.  */
+/* { dg-options "-mno-pcrel" } */
+
+/* Verify one error emitted for unexpected 4 nops before local
+   entry.  */
+
+extern int a;
+
+__attribute__ ((patchable_function_entry (20, 4)))
+int test (int b) {
+  return a + b;
+}
+/* { dg-error "unsupported number of nops before function entry \\(4\\)" "" { target *-*-* } .-1 } */
--
2.27.0




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-- links below jump to the message on this page --
2022-08-25  5:50 [PATCH v4] rs6000: Rework ELFv2 support for -fpatchable-function-entry* [PR99888] Kewen.Lin
2022-09-28  5:37 ` PING^1 " Kewen.Lin
2022-09-28 15:22 ` Segher Boessenkool
2022-09-30 12:38   ` Kewen.Lin

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