On 2023-10-16, Uros Bizjak wrote:
On Tue, Aug 1, 2023 at 9:51 PM Fangrui Song <mask...@google.com> wrote:
When using -mcmodel=medium, large data objects larger than the
-mlarge-data-threshold threshold are placed into large data sections
(.lrodata, .ldata, .lbss and some variants). GNU ld and ld.lld 17 place
.l* sections into separate output sections. If small and medium code
model object files are mixed, the .l* sections won't exert relocation
overflow pressure on sections in object files built with -mcmodel=small.
However, when using -mcmodel=large, -mlarge-data-threshold doesn't
apply. This means that the .rodata/.data/.bss sections may exert
relocation overflow pressure on sections in -mcmodel=small object files.
This patch allows -mcmodel=large to generate .l* sections and drops an
unneeded documentation restriction that the value must be the same.
Link: https://groups.google.com/g/x86-64-abi/c/jnQdJeabxiU
("Large data sections for the large code model")
Signed-off-by: Fangrui Song <mask...@google.com>
---
Changes from v1
(https://gcc.gnu.org/pipermail/gcc-patches/2023-April/616947.html):
* Clarify commit message. Add link to
https://groups.google.com/g/x86-64-abi/c/jnQdJeabxiU
Changes from v2
* Drop an uneeded limitation in the documentation.
Changes from v3
* Change scan-assembler directives to use \. to match literal .
---
gcc/config/i386/i386.cc | 15 +++++++++------
gcc/config/i386/i386.opt | 2 +-
gcc/doc/invoke.texi | 6 +++---
gcc/testsuite/gcc.target/i386/large-data.c | 13 +++++++++++++
4 files changed, 26 insertions(+), 10 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/i386/large-data.c
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index eabc70011ea..37e810cc741 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -647,7 +647,8 @@ ix86_can_inline_p (tree caller, tree callee)
static bool
ix86_in_large_data_p (tree exp)
{
- if (ix86_cmodel != CM_MEDIUM && ix86_cmodel != CM_MEDIUM_PIC)
+ if (ix86_cmodel != CM_MEDIUM && ix86_cmodel != CM_MEDIUM_PIC &&
+ ix86_cmodel != CM_LARGE && ix86_cmodel != CM_LARGE_PIC)
Please split multi-line expression before the operator, not after it,
as instructed in GNU Coding Standards [1] ...
[1] https://www.gnu.org/prep/standards/html_node/Formatting.html
return false;
if (exp == NULL_TREE)
@@ -858,8 +859,9 @@ x86_elf_aligned_decl_common (FILE *file, tree decl,
const char *name, unsigned HOST_WIDE_INT size,
unsigned align)
{
- if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC)
- && size > (unsigned int)ix86_section_threshold)
+ if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC ||
+ ix86_cmodel == CM_LARGE || ix86_cmodel == CM_LARGE_PIC) &&
+ size > (unsigned int)ix86_section_threshold)
... also here ...
{
switch_to_section (get_named_section (decl, ".lbss", 0));
fputs (LARGECOMM_SECTION_ASM_OP, file);
@@ -879,9 +881,10 @@ void
x86_output_aligned_bss (FILE *file, tree decl, const char *name,
unsigned HOST_WIDE_INT size, unsigned align)
{
- if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC)
- && size > (unsigned int)ix86_section_threshold)
- switch_to_section (get_named_section (decl, ".lbss", 0));
+ if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC ||
+ ix86_cmodel == CM_LARGE || ix86_cmodel == CM_LARGE_PIC) &&
+ size > (unsigned int)ix86_section_threshold)
... and here.
OK with these formatting changes.
Thanks,
Uros.
Thank you for the review!
Posted PATCH v5
https://gcc.gnu.org/pipermail/gcc-patches/2023-October/633153.html
with the formatting.
I don't have write access to the gcc repository:)
(Hmmm... in emacs, C-c . gnu RET C-M-\ doesn't fix the && || formatting
errors.)
+ switch_to_section(get_named_section(decl, ".lbss", 0));
else
switch_to_section (bss_section);
ASM_OUTPUT_ALIGN (file, floor_log2 (align / BITS_PER_UNIT));
diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
index 1cc8563477a..52fad492353 100644
--- a/gcc/config/i386/i386.opt
+++ b/gcc/config/i386/i386.opt
@@ -282,7 +282,7 @@ Branches are this expensive (arbitrary units).
mlarge-data-threshold=
Target RejectNegative Joined UInteger Var(ix86_section_threshold)
Init(DEFAULT_LARGE_SECTION_THRESHOLD)
--mlarge-data-threshold=<number> Data greater than given threshold will
go into .ldata section in x86-64 medium model.
+-mlarge-data-threshold=<number> Data greater than given threshold will
go into a large data section in x86-64 medium and large code models.
mcmodel=
Target RejectNegative Joined Enum(cmodel) Var(ix86_cmodel) Init(CM_32)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 104766f446d..bf6fe3e1a20 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -33207,9 +33207,9 @@ the cache line size. @samp{compat} is the default.
@opindex mlarge-data-threshold
@item -mlarge-data-threshold=@var{threshold}
-When @option{-mcmodel=medium} is specified, data objects larger than
-@var{threshold} are placed in the large data section. This value must be the
-same across all objects linked into the binary, and defaults to 65535.
+When @option{-mcmodel=medium} or @option{-mcmodel=large} is specified, data
+objects larger than @var{threshold} are placed in large data sections. The
+default is 65535.
@opindex mrtd
@item -mrtd
diff --git a/gcc/testsuite/gcc.target/i386/large-data.c
b/gcc/testsuite/gcc.target/i386/large-data.c
new file mode 100644
index 00000000000..bdd4acd30b8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/large-data.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-O2 -mcmodel=large -mlarge-data-threshold=4" } */
+/* { dg-final { scan-assembler {\.lbss} } } */
+/* { dg-final { scan-assembler {\.bss} } } */
+/* { dg-final { scan-assembler {\.ldata} } } */
+/* { dg-final { scan-assembler {\.data} } } */
+/* { dg-final { scan-assembler {\.lrodata} } } */
+/* { dg-final { scan-assembler {\.rodata} } } */
+
+const char rodata_a[] = "abc", rodata_b[] = "abcd";
+char data_a[4] = {1}, data_b[5] = {1};
+char bss_a[4], bss_b[5];
--
2.41.0.585.gd2178a4bd4-goog
From da49445a50c57b583201e3fb48fa91781b9ec761 Mon Sep 17 00:00:00 2001
From: Fangrui Song <mask...@google.com>
Date: Thu, 27 Apr 2023 12:29:31 -0700
Subject: [PATCH v5] i386: Allow -mlarge-data-threshold with -mcmodel=large
When using -mcmodel=medium, large data objects larger than the
-mlarge-data-threshold threshold are placed into large data sections
(.lrodata, .ldata, .lbss and some variants). GNU ld and ld.lld 17 place
.l* sections into separate output sections. If small and medium code
model object files are mixed, the .l* sections won't exert relocation
overflow pressure on sections in object files built with -mcmodel=small.
However, when using -mcmodel=large, -mlarge-data-threshold doesn't
apply. This means that the .rodata/.data/.bss sections may exert
relocation overflow pressure on sections in -mcmodel=small object files.
This patch allows -mcmodel=large to generate .l* sections and drops an
unneeded documentation restriction that the value must be the same.
Link: https://groups.google.com/g/x86-64-abi/c/jnQdJeabxiU
("Large data sections for the large code model")
Signed-off-by: Fangrui Song <mask...@google.com>
---
Changes from v1
(https://gcc.gnu.org/pipermail/gcc-patches/2023-April/616947.html):
* Clarify commit message. Add link to
https://groups.google.com/g/x86-64-abi/c/jnQdJeabxiU
Changes from v2
* Drop an uneeded limitation in the documentation.
Changes from v3
* Change scan-assembler directives to use \. to match literal .
Changes from v4
(https://gcc.gnu.org/pipermail/gcc-patches/2023-October/633145.html)
* "When you split an expression into multiple lines, split it before an operator,
not after one."
---
gcc/config/i386/i386.cc | 9 ++++++---
gcc/config/i386/i386.opt | 2 +-
gcc/doc/invoke.texi | 6 +++---
gcc/testsuite/gcc.target/i386/large-data.c | 13 +++++++++++++
4 files changed, 23 insertions(+), 7 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/i386/large-data.c
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 8251b67e2d6..641e7680335 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -663,7 +663,8 @@ ix86_can_inline_p (tree caller, tree callee)
static bool
ix86_in_large_data_p (tree exp)
{
- if (ix86_cmodel != CM_MEDIUM && ix86_cmodel != CM_MEDIUM_PIC)
+ if (ix86_cmodel != CM_MEDIUM && ix86_cmodel != CM_MEDIUM_PIC
+ && ix86_cmodel != CM_LARGE && ix86_cmodel != CM_LARGE_PIC)
return false;
if (exp == NULL_TREE)
@@ -874,7 +875,8 @@ x86_elf_aligned_decl_common (FILE *file, tree decl,
const char *name, unsigned HOST_WIDE_INT size,
unsigned align)
{
- if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC)
+ if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC
+ || ix86_cmodel == CM_LARGE || ix86_cmodel == CM_LARGE_PIC)
&& size > (unsigned int)ix86_section_threshold)
{
switch_to_section (get_named_section (decl, ".lbss", 0));
@@ -895,7 +897,8 @@ void
x86_output_aligned_bss (FILE *file, tree decl, const char *name,
unsigned HOST_WIDE_INT size, unsigned align)
{
- if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC)
+ if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC
+ || ix86_cmodel == CM_LARGE || ix86_cmodel == CM_LARGE_PIC)
&& size > (unsigned int)ix86_section_threshold)
switch_to_section (get_named_section (decl, ".lbss", 0));
else
diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
index b8382c48099..0c3b8f4b621 100644
--- a/gcc/config/i386/i386.opt
+++ b/gcc/config/i386/i386.opt
@@ -282,7 +282,7 @@ Branches are this expensive (arbitrary units).
mlarge-data-threshold=
Target RejectNegative Joined UInteger Var(ix86_section_threshold)
Init(DEFAULT_LARGE_SECTION_THRESHOLD)
--mlarge-data-threshold=<number> Data greater than given threshold will go
into .ldata section in x86-64 medium model.
+-mlarge-data-threshold=<number> Data greater than given threshold will go
into a large data section in x86-64 medium and large code models.
mcmodel=
Target RejectNegative Joined Enum(cmodel) Var(ix86_cmodel) Init(CM_32)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index eb714d18511..50745a3a195 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -33390,9 +33390,9 @@ the cache line size. @samp{compat} is the default.
@opindex mlarge-data-threshold
@item -mlarge-data-threshold=@var{threshold}
-When @option{-mcmodel=medium} is specified, data objects larger than
-@var{threshold} are placed in the large data section. This value must be the
-same across all objects linked into the binary, and defaults to 65535.
+When @option{-mcmodel=medium} or @option{-mcmodel=large} is specified, data
+objects larger than @var{threshold} are placed in large data sections. The
+default is 65535.
@opindex mrtd
@item -mrtd
diff --git a/gcc/testsuite/gcc.target/i386/large-data.c
b/gcc/testsuite/gcc.target/i386/large-data.c
new file mode 100644
index 00000000000..bdd4acd30b8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/large-data.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-O2 -mcmodel=large -mlarge-data-threshold=4" } */
+/* { dg-final { scan-assembler {\.lbss} } } */
+/* { dg-final { scan-assembler {\.bss} } } */
+/* { dg-final { scan-assembler {\.ldata} } } */
+/* { dg-final { scan-assembler {\.data} } } */
+/* { dg-final { scan-assembler {\.lrodata} } } */
+/* { dg-final { scan-assembler {\.rodata} } } */
+
+const char rodata_a[] = "abc", rodata_b[] = "abcd";
+char data_a[4] = {1}, data_b[5] = {1};
+char bss_a[4], bss_b[5];
--
2.42.0.655.g421f12c284-goog
