On 26 September 2024 20:51:55 CEST, Fangrui Song <mask...@google.com> wrote:
>On Thu, Sep 26, 2024 at 11:21 AM Ramana Radhakrishnan
><ramana....@googlemail.com> wrote:
>>
>> On Mon, Mar 4, 2024 at 1:43 PM Fangrui Song <mask...@google.com> wrote:
>> >
>> > From: Fangrui Song <mask...@gcc.gnu.org>
>> >
>> > -fno-pic -mfdpic generated code is like regular -fno-pic, not suitable
>> > for FDPIC (absolute addressing for symbol references and no function
>> > descriptor). The sh port simply upgrades -fno-pic to -fpie by setting
>> > flag_pic. Let's follow suit.
>> >
>> > Link:
>> > https://inbox.sourceware.org/gcc-patches/20150913165303.gc17...@brightrain.aerifal.cx/
>> >
>> > gcc/ChangeLog:
>> >
>> > * config/arm/arm.cc (arm_option_override): Set flag_pic if
>> > TARGET_FDPIC.
>> >
>> > gcc/testsuite/ChangeLog:
>> >
>> > * gcc.target/arm/fdpic-pie.c: New test.
>> > ---
>> > gcc/config/arm/arm.cc | 6 +++++
>> > gcc/testsuite/gcc.target/arm/fdpic-pie.c | 30 ++++++++++++++++++++++++
>> > 2 files changed, 36 insertions(+)
>> > create mode 100644 gcc/testsuite/gcc.target/arm/fdpic-pie.c
>> >
>> > diff --git a/gcc/config/arm/arm.cc b/gcc/config/arm/arm.cc
>> > index 1cd69268ee9..f2fd3cce48c 100644
>> > --- a/gcc/config/arm/arm.cc
>> > +++ b/gcc/config/arm/arm.cc
>> > @@ -3682,6 +3682,12 @@ arm_option_override (void)
>> > arm_pic_register = FDPIC_REGNUM;
>> > if (TARGET_THUMB1)
>> > sorry ("FDPIC mode is not supported in Thumb-1 mode");
>> > +
>> > + /* FDPIC code is a special form of PIC, and the vast majority of
>> > code
>> > + generation constraints that apply to PIC also apply to FDPIC, so
>> > we
>> > + set flag_pic to avoid the need to check TARGET_FDPIC everywhere
>> > + flag_pic is checked. */
>> > + flag_pic = 2;
>> > }
>>
>> Been a while since I looked at this stuff but should this not be
>> flag_pie being set rather than flag_pic here if the expectation is to
>> turn -fno-PIC -mfdpic into fPIE ?
>
>I think flag_pic determines the PIC/PIE vs no-PIC difference
>while flag_shlib determines the PIC vs PIE difference (whether
>non-local default linkage symbol might bind externally).
>
>Setting flag_pic here is correct.
indeed.
pic 2 lgtm
thanks
>
>>
>> >
>> > if (arm_pic_register_string != NULL)
>> > diff --git a/gcc/testsuite/gcc.target/arm/fdpic-pie.c
>> > b/gcc/testsuite/gcc.target/arm/fdpic-pie.c
>> > new file mode 100644
>> > index 00000000000..909db8bce74
>> > --- /dev/null
>> > +++ b/gcc/testsuite/gcc.target/arm/fdpic-pie.c
>> > @@ -0,0 +1,30 @@
>> > +// { dg-do compile }
>> > +// { dg-options "-O2 -fno-pic -mfdpic" }
>> > +// { dg-skip-if "-mpure-code and -fPIC incompatible" { *-*-* } {
>> > "-mpure-code" } }
>> > +
>> > +__attribute__((visibility("hidden"))) void hidden_fun(void);
>> > +void fun(void);
>> > +__attribute__((visibility("hidden"))) extern int hidden_var;
>> > +extern int var;
>> > +__attribute__((visibility("hidden"))) const int ro_hidden_var = 42;
>> > +
>> > +// { dg-final { scan-assembler "hidden_fun\\(GOTOFFFUNCDESC\\)" } }
>> > +void *addr_hidden_fun(void) { return hidden_fun; }
>> > +
>> > +// { dg-final { scan-assembler "fun\\(GOTFUNCDESC\\)" } }
>> > +void *addr_fun(void) { return fun; }
>> > +
>> > +// { dg-final { scan-assembler "hidden_var\\(GOT\\)" } }
>> > +void *addr_hidden_var(void) { return &hidden_var; }
>> > +
>> > +// { dg-final { scan-assembler "var\\(GOT\\)" } }
>> > +void *addr_var(void) { return &var; }
>> > +
>> > +// { dg-final { scan-assembler ".LANCHOR0\\(GOT\\)" } }
>> > +const int *addr_ro_hidden_var(void) { return &ro_hidden_var; }
>> > +
>> > +// { dg-final { scan-assembler "hidden_var\\(GOT\\)" } }
>> > +int read_hidden_var(void) { return hidden_var; }
>> > +
>> > +// { dg-final { scan-assembler "var\\(GOT\\)" } }
>> > +int read_var(void) { return var; }
>> > --
>> > 2.44.0.rc1.240.g4c46232300-goog
>> >
>
>
>
