[PATCH] rs6000: Avoid -fpatchable-function-entry* regressions on powerpc64 be [PR98125]
Jakub Jelinek
jakub@redhat.com
Wed Mar 31 12:49:29 GMT 2021
Hi!
The SECTION_LINK_ORDER changes broke powerpc64-linux ELFv1. Seems
that the assembler/linker relies on the symbol mentioned for the
"awo" section to be in the same section as the symbols mentioned in
the relocations in that section (i.e. labels for the patchable area
in this case). That is the case for most targets, including powerpc-linux
32-bit or powerpc64 ELFv2 (that one has -fpatchable-function-entry*
support broken for other reasons and it doesn't seem to be a regression).
But it doesn't work on powerpc64-linux ELFv1.
We emit:
.section ".opd","aw"
.align 3
_Z3foov:
.quad .L._Z3foov,.TOC.@tocbase,0
.previous
.type _Z3foov, @function
.L._Z3foov:
.section __patchable_function_entries,"awo",@progbits,_Z3foov
.align 3
.8byte .LPFE1
.section .text._Z3foov,"axG",@progbits,_Z3foov,comdat
.LPFE1:
nop
.LFB0:
.cfi_startproc
and because _Z3foov is in the .opd section rather than the function text
section, it doesn't work.
I'm afraid I don't know what exactly should be done, whether e.g.
it could use
.section __patchable_function_entries,"awo",@progbits,.L._Z3foov
instead, or whether the linker should be changed to handle it as is, or
something else.
But because we have a P1 regression that didn't see useful progress over the
4 months since it has been filed and we don't really have much time, below
is an attempt to do a targetted reversion of H.J's patch, basically act as
if HAVE_GAS_SECTION_LINK_ORDER is never true for powerpc64-linux ELFv1,
but for 32-bit or 64-bit ELFv2 keep working as is.
This would give us time to resolve it for GCC 12 properly.
Bootstrapped/regtested on powerpc64-linux (regtest with both -m32/-m64).
2021-03-31 Jakub Jelinek <jakub@redhat.com>
PR testsuite/98125
* targhooks.h (default_print_patchable_function_entry_1): Declare.
* targhooks.c (default_print_patchable_function_entry_1): New function,
copied from default_print_patchable_function_entry with an added flags
argument.
(default_print_patchable_function_entry): Rewritten into a small
wrapper around default_print_patchable_function_entry_1.
* config/rs6000/rs6000.c (TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY):
Redefine.
(rs6000_print_patchable_function_entry): New function.
* g++.dg/pr93195a.C: Skip on powerpc*-*-* 64-bit.
--- gcc/targhooks.h.jj 2021-01-04 10:25:39.665224403 +0100
+++ gcc/targhooks.h 2021-03-30 15:48:42.826706369 +0200
@@ -230,6 +230,9 @@ extern bool default_use_by_pieces_infras
bool);
extern int default_compare_by_pieces_branch_ratio (machine_mode);
+extern void default_print_patchable_function_entry_1 (FILE *,
+ unsigned HOST_WIDE_INT,
+ bool, unsigned int);
extern void default_print_patchable_function_entry (FILE *,
unsigned HOST_WIDE_INT,
bool);
--- gcc/targhooks.c.jj 2021-01-04 10:25:38.974232228 +0100
+++ gcc/targhooks.c 2021-03-30 15:51:22.924932795 +0200
@@ -1832,17 +1832,15 @@ default_compare_by_pieces_branch_ratio (
return 1;
}
-/* Write PATCH_AREA_SIZE NOPs into the asm outfile FILE around a function
- entry. If RECORD_P is true and the target supports named sections,
- the location of the NOPs will be recorded in a special object section
- called "__patchable_function_entries". This routine may be called
- twice per function to put NOPs before and after the function
- entry. */
+/* Helper for default_print_patchable_function_entry and other
+ print_patchable_function_entry hook implementations. */
void
-default_print_patchable_function_entry (FILE *file,
- unsigned HOST_WIDE_INT patch_area_size,
- bool record_p)
+default_print_patchable_function_entry_1 (FILE *file,
+ unsigned HOST_WIDE_INT
+ patch_area_size,
+ bool record_p,
+ unsigned int flags)
{
const char *nop_templ = 0;
int code_num;
@@ -1864,9 +1862,6 @@ default_print_patchable_function_entry (
patch_area_number++;
ASM_GENERATE_INTERNAL_LABEL (buf, "LPFE", patch_area_number);
- unsigned int flags = SECTION_WRITE | SECTION_RELRO;
- if (HAVE_GAS_SECTION_LINK_ORDER)
- flags |= SECTION_LINK_ORDER;
switch_to_section (get_section ("__patchable_function_entries",
flags, current_function_decl));
assemble_align (POINTER_SIZE);
@@ -1883,6 +1878,25 @@ default_print_patchable_function_entry (
output_asm_insn (nop_templ, NULL);
}
+/* Write PATCH_AREA_SIZE NOPs into the asm outfile FILE around a function
+ entry. If RECORD_P is true and the target supports named sections,
+ the location of the NOPs will be recorded in a special object section
+ called "__patchable_function_entries". This routine may be called
+ twice per function to put NOPs before and after the function
+ entry. */
+
+void
+default_print_patchable_function_entry (FILE *file,
+ unsigned HOST_WIDE_INT patch_area_size,
+ bool record_p)
+{
+ unsigned int flags = SECTION_WRITE | SECTION_RELRO;
+ if (HAVE_GAS_SECTION_LINK_ORDER)
+ flags |= SECTION_LINK_ORDER;
+ default_print_patchable_function_entry_1 (file, patch_area_size, record_p,
+ flags);
+}
+
bool
default_profile_before_prologue (void)
{
--- gcc/config/rs6000/rs6000.c.jj 2021-03-29 11:15:49.942202792 +0200
+++ gcc/config/rs6000/rs6000.c 2021-03-30 15:59:10.299755166 +0200
@@ -1341,6 +1341,9 @@ static const struct attribute_spec rs600
#define TARGET_ASM_ASSEMBLE_VISIBILITY rs6000_assemble_visibility
#endif
+#undef TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY
+#define TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY rs6000_print_patchable_function_entry
+
#undef TARGET_SET_UP_BY_PROLOGUE
#define TARGET_SET_UP_BY_PROLOGUE rs6000_set_up_by_prologue
@@ -14642,6 +14645,30 @@ rs6000_assemble_visibility (tree decl, i
}
#endif
+/* Write PATCH_AREA_SIZE NOPs into the asm outfile FILE around a function
+ entry. If RECORD_P is true and the target supports named sections,
+ the location of the NOPs will be recorded in a special object section
+ called "__patchable_function_entries". This routine may be called
+ twice per function to put NOPs before and after the function
+ entry. */
+
+void
+rs6000_print_patchable_function_entry (FILE *file,
+ unsigned HOST_WIDE_INT patch_area_size,
+ bool record_p)
+{
+ unsigned int flags = SECTION_WRITE | SECTION_RELRO;
+ /* When .opd section is emitted, the function symbol
+ default_print_patchable_function_entry_1 is emitted into the .opd section
+ while the patchable area is emitted into the function section.
+ Don't use SECTION_LINK_ORDER in that case. */
+ 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);
+}
+
enum rtx_code
rs6000_reverse_condition (machine_mode mode, enum rtx_code code)
{
--- gcc/testsuite/g++.dg/pr93195a.C.jj 2020-12-02 14:42:52.216054386 +0100
+++ gcc/testsuite/g++.dg/pr93195a.C 2021-03-30 17:09:06.529574261 +0200
@@ -1,4 +1,5 @@
/* { dg-do link { target { ! { nvptx*-*-* visium-*-* } } } } */
+/* { dg-skip-if "not supported yet" { { powerpc*-*-* } && lp64 } } */
// { dg-require-effective-target o_flag_in_section }
/* { dg-options "-O0 -fpatchable-function-entry=1" } */
/* { dg-additional-options "-fno-pie" { target sparc*-*-* } } */
Jakub
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