As observed a number of years ago in the following thread, i386/i386elf.h has
not been kept up to date:
https://gcc.gnu.org/pipermail/gcc/2013-August/209981.html
This patch does the following cleanup:
1. The return convention now follows the i386 and x86_64 SVR4 ABIs again. As
discussed in the above thread, the current return convention does not match any
other target or existing ABI, which is problematic since the current approach
is inefficient (particularly on x86_64-elf) and confuses other tools like GDB
(unfortunately that thread did not lead to any fix at the time).
2. The default version of ASM_OUTPUT_ASCII from elfos.h is used. As mentioned
in the cleanup of i386/sysv4.h [1] the ASM_OUTPUT_ASCII implementation then
used by sysv4.h, and currently used by i386elf.h, has a significantly higher
computation complexity than the default version provided by elfos.h.
The patch has been tested on i386-elf and x86_64-elf hosted on x86_64-linux,
fixing a number failing tests that were expecting the SVR4 ABI return
convention. It has also been bootstrapped and tested on x86_64-pc-linux-gnu
without regression.
If approved, I'll need a maintainer to kindly commit on my behalf.
Thanks,
Pat Bernardi
Senior Software Engineer, AdaCore
[1] https://gcc.gnu.org/pipermail/gcc-patches/2011-February/305559.html
2020-08-18 Pat Bernardi <berna...@adacore.com>
gcc/ChangeLog
* config/i386/i386elf.h (SUBTARGET_RETURN_IN_MEMORY): Remove.
(ASM_OUTPUT_ASCII): Likewise.
(DEFAULT_PCC_STRUCT_RETURN): Define.
* config/i386/i386.c (ix86_return_in_memory): Remove
SUBTARGET_RETURN_IN_MEMORY.
From fe617455561a4c8d898b4e231c447b16e5661e10 Mon Sep 17 00:00:00 2001
From: Pat Bernardi <berna...@adacore.com>
Date: Fri, 14 Aug 2020 17:34:38 -0400
Subject: [PATCH] i386: Cleanup i386/i386elf.h and align it's return convention
with the SVR4 ABI
While i386elf.h was originally derived from sysv4.h it has not been kept
up to date with the development of the compiler. Two changes are made:
* The return convention now follows the i386 and x86_64 SVR4 ABIs again.
* The more efficient default version of ASM_OUTPUT_ASCII in elfos.h is used.
2020-08-18 Pat Bernardi <berna...@adacore.com>
gcc/ChangeLog
* config/i386/i386elf.h (SUBTARGET_RETURN_IN_MEMORY): Remove.
(ASM_OUTPUT_ASCII): Likewise.
(DEFAULT_PCC_STRUCT_RETURN): Define.
* config/i386/i386.c (ix86_return_in_memory): Remove
SUBTARGET_RETURN_IN_MEMORY.
---
gcc/config/i386/i386.c | 4 ---
gcc/config/i386/i386elf.h | 62 ++++-----------------------------------
2 files changed, 6 insertions(+), 60 deletions(-)
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index e9ecb94d174..65e87b41e80 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -3796,9 +3796,6 @@ ix86_libcall_value (machine_mode mode)
static bool
ix86_return_in_memory (const_tree type, const_tree fntype ATTRIBUTE_UNUSED)
{
-#ifdef SUBTARGET_RETURN_IN_MEMORY
- return SUBTARGET_RETURN_IN_MEMORY (type, fntype);
-#else
const machine_mode mode = type_natural_mode (type, NULL, true);
HOST_WIDE_INT size;
@@ -3879,7 +3876,6 @@ ix86_return_in_memory (const_tree type, const_tree fntype
ATTRIBUTE_UNUSED)
return false;
}
-#endif
}
diff --git a/gcc/config/i386/i386elf.h b/gcc/config/i386/i386elf.h
index eb2203cf323..05cee89f795 100644
--- a/gcc/config/i386/i386elf.h
+++ b/gcc/config/i386/i386elf.h
@@ -19,12 +19,12 @@ You should have received a copy of the GNU General Public
License
along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
-/* The ELF ABI for the i386 says that records and unions are returned
- in memory. */
-
-#define SUBTARGET_RETURN_IN_MEMORY(TYPE, FNTYPE) \
- (TYPE_MODE (TYPE) == BLKmode \
- || (VECTOR_MODE_P (TYPE_MODE (TYPE)) && int_size_in_bytes (TYPE) == 8))
+/* Define DEFAULT_PCC_STRUCT_RETURN to 1 because the i386 SVR4 ABI returns
+ records and unions in memory. ix86_option_override_internal will overide
+ this flag when compiling 64-bit code as we never do pcc_struct_return
+ scheme on x86-64. */
+#undef DEFAULT_PCC_STRUCT_RETURN
+#define DEFAULT_PCC_STRUCT_RETURN 1
#undef CPP_SPEC
#define CPP_SPEC ""
@@ -40,56 +40,6 @@ along with GCC; see the file COPYING3. If not see
#define DBX_REGISTER_NUMBER(n) \
(TARGET_64BIT ? dbx64_register_map[n] : svr4_dbx_register_map[n])
-/* The routine used to output sequences of byte values. We use a special
- version of this for most svr4 targets because doing so makes the
- generated assembly code more compact (and thus faster to assemble)
- as well as more readable. Note that if we find subparts of the
- character sequence which end with NUL (and which are shorter than
- ELF_STRING_LIMIT) we output those using ASM_OUTPUT_LIMITED_STRING. */
-
-#undef ASM_OUTPUT_ASCII
-#define ASM_OUTPUT_ASCII(FILE, STR, LENGTH) \
- do \
- { \
- const unsigned char *_ascii_bytes = \
- (const unsigned char *) (STR); \
- const unsigned char *limit = _ascii_bytes + (LENGTH); \
- unsigned bytes_in_chunk = 0; \
- for (; _ascii_bytes < limit; _ascii_bytes++) \
- { \
- const unsigned char *p; \
- if (bytes_in_chunk >= 64) \
- { \
- fputc ('\n', (FILE)); \
- bytes_in_chunk = 0; \
- } \
- for (p = _ascii_bytes; p < limit && *p != '\0'; p++) \
- continue; \
- if (p < limit && (p - _ascii_bytes) <= (long) ELF_STRING_LIMIT) \
- { \
- if (bytes_in_chunk > 0) \
- { \
- fputc ('\n', (FILE)); \
- bytes_in_chunk = 0; \
- } \
- ASM_OUTPUT_LIMITED_STRING ((FILE), (const char *) _ascii_bytes); \
- _ascii_bytes = p; \
- } \
- else \
- { \
- if (bytes_in_chunk == 0) \
- fputs (ASM_BYTE, (FILE)); \
- else \
- fputc (',', (FILE)); \
- fprintf ((FILE), "0x%02x", *_ascii_bytes);
\
- bytes_in_chunk += 5; \
- } \
- } \
- if (bytes_in_chunk > 0) \
- fputc ('\n', (FILE)); \
- } \
- while (0)
-
#define LOCAL_LABEL_PREFIX "."
/* Switch into a generic section. */
--
2.27.0
