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. > + 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 >