Hi, This patch implements the alternate code sequence recommended in
https://groups.google.com/forum/#!topic/x86-64-abi/de5_KnLHxtI to load external function address via GOT slot with movq func@GOTPCREL(%rip), %rax so that linker won't create an PLT entry for extern function address. Tested on x86-64. OK for trunk? H.J. -- gcc/ PR target/67400 * config/i386/i386-protos.h (ix86_force_load_from_GOT_p): New. * config/i386/i386.c (ix86_force_load_from_GOT_p): New function. (ix86_legitimate_address_p): Allow UNSPEC_GOTPCREL if ix86_force_load_from_GOT_p returns true. (ix86_print_operand_address): Support UNSPEC_GOTPCREL if ix86_force_load_from_GOT_p returns true. (ix86_expand_move): Load the external function address via the GOT slot if ix86_force_load_from_GOT_p returns true. * config/i386/predicates.md (x86_64_immediate_operand): Return false if ix86_force_load_from_GOT_p returns true. gcc/testsuite/ PR target/67400 * gcc.target/i386/pr67400-1.c: New test. * gcc.target/i386/pr67400-2.c: Likewise. * gcc.target/i386/pr67400-3.c: Likewise. * gcc.target/i386/pr67400-4.c: Likewise. * gcc.target/i386/pr67400-5.c: Likewise. * gcc.target/i386/pr67400-6.c: Likewise. --- gcc/config/i386/i386-protos.h | 1 + gcc/config/i386/i386.c | 51 +++++++++++++++++++++++++++++++ gcc/config/i386/predicates.md | 4 +++ gcc/testsuite/gcc.target/i386/pr67400-1.c | 13 ++++++++ gcc/testsuite/gcc.target/i386/pr67400-2.c | 14 +++++++++ gcc/testsuite/gcc.target/i386/pr67400-3.c | 16 ++++++++++ gcc/testsuite/gcc.target/i386/pr67400-4.c | 13 ++++++++ gcc/testsuite/gcc.target/i386/pr67400-5.c | 11 +++++++ gcc/testsuite/gcc.target/i386/pr67400-6.c | 13 ++++++++ 9 files changed, 136 insertions(+) create mode 100644 gcc/testsuite/gcc.target/i386/pr67400-1.c create mode 100644 gcc/testsuite/gcc.target/i386/pr67400-2.c create mode 100644 gcc/testsuite/gcc.target/i386/pr67400-3.c create mode 100644 gcc/testsuite/gcc.target/i386/pr67400-4.c create mode 100644 gcc/testsuite/gcc.target/i386/pr67400-5.c create mode 100644 gcc/testsuite/gcc.target/i386/pr67400-6.c diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h index 9fd14f6..8130161 100644 --- a/gcc/config/i386/i386-protos.h +++ b/gcc/config/i386/i386-protos.h @@ -70,6 +70,7 @@ extern bool ix86_expand_set_or_movmem (rtx, rtx, rtx, rtx, rtx, rtx, extern bool constant_address_p (rtx); extern bool legitimate_pic_operand_p (rtx); extern bool legitimate_pic_address_disp_p (rtx); +extern bool ix86_force_load_from_GOT_p (rtx); extern void print_reg (rtx, int, FILE*); extern void ix86_print_operand (FILE *, rtx, int); diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c index 56a5b9c..c8c5081 100644 --- a/gcc/config/i386/i386.c +++ b/gcc/config/i386/i386.c @@ -15182,6 +15182,24 @@ ix86_legitimate_constant_p (machine_mode mode, rtx x) return true; } +/* True if operand X should be loaded from GOT. */ + +bool +ix86_force_load_from_GOT_p (rtx x) +{ + /* External function symbol should be loaded via the GOT slot for + -fno-plt. */ + return (!flag_plt + && !flag_pic + && ix86_cmodel != CM_LARGE + && TARGET_64BIT + && !TARGET_PECOFF + && !TARGET_MACHO + && GET_CODE (x) == SYMBOL_REF + && SYMBOL_REF_FUNCTION_P (x) + && !SYMBOL_REF_LOCAL_P (x)); +} + /* Determine if it's legal to put X into the constant pool. This is not possible for the address of thread-local symbols, which is checked above. */ @@ -15560,6 +15578,10 @@ ix86_legitimate_address_p (machine_mode, rtx addr, bool strict) return false; case UNSPEC_GOTPCREL: + gcc_assert (flag_pic + || ix86_force_load_from_GOT_p (XVECEXP (XEXP (disp, 0), 0, 0))); + goto is_legitimate_pic; + case UNSPEC_PCREL: gcc_assert (flag_pic); goto is_legitimate_pic; @@ -18130,6 +18152,12 @@ ix86_print_operand_address_as (FILE *file, rtx addr, } else if (flag_pic) output_pic_addr_const (file, disp, 0); + else if (GET_CODE (disp) == CONST + && GET_CODE (XEXP (disp, 0)) == UNSPEC + && (XINT (XEXP (disp, 0), 1) == UNSPEC_GOTPCREL + || XINT (XEXP (disp, 0), 1) == UNSPEC_GOT) + && ix86_force_load_from_GOT_p (XVECEXP (XEXP (disp, 0), 0, 0))) + output_pic_addr_const (file, XEXP (disp, 0), code); else output_addr_const (file, disp); } @@ -19448,6 +19476,29 @@ ix86_expand_move (machine_mode mode, rtx operands[]) op1 = convert_to_mode (mode, op1, 1); } } + } + else if (ix86_force_load_from_GOT_p (op1)) + { + /* Load the external function address via the GOT slot to + avoid PLT. */ + op1 = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, op1), + (TARGET_64BIT + ? UNSPEC_GOTPCREL + : UNSPEC_GOT)); + op1 = gen_rtx_CONST (Pmode, op1); + op1 = gen_const_mem (Pmode, op1); + /* This symbol must be referenced via a load from the Global + Offset Table. */ + set_mem_alias_set (op1, ix86_GOT_alias_set ()); + op1 = convert_to_mode (mode, op1, 1); + op1 = force_reg (mode, op1); + emit_insn (gen_rtx_SET (op0, op1)); + /* Generate a CLOBBER so that there will be no REG_EQUAL note + on the last insn to prevent cse and fwprop from replacing + a GOT load with a constant. */ + rtx tmp = gen_reg_rtx (Pmode); + emit_clobber (tmp); + return; } else { diff --git a/gcc/config/i386/predicates.md b/gcc/config/i386/predicates.md index b3cf2a3..06a0002 100644 --- a/gcc/config/i386/predicates.md +++ b/gcc/config/i386/predicates.md @@ -149,6 +149,10 @@ (define_predicate "x86_64_immediate_operand" (match_code "const_int,symbol_ref,label_ref,const") { + /* Load the external function address via the GOT slot to avoid PLT. */ + if (ix86_force_load_from_GOT_p (op)) + return false; + if (!TARGET_64BIT) return immediate_operand (op, mode); diff --git a/gcc/testsuite/gcc.target/i386/pr67400-1.c b/gcc/testsuite/gcc.target/i386/pr67400-1.c new file mode 100644 index 0000000..a875b76 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr67400-1.c @@ -0,0 +1,13 @@ +/* { dg-do compile { target *-*-linux* } } */ +/* { dg-options "-O2 -fno-pic -fno-plt" } */ + +extern void bar (void); + +void * +foo (void) +{ + return &bar; +} + +/* { dg-final { scan-assembler "mov\(l|q\)\[ \t\]*bar@GOTPCREL" { target { ! ia32 } } } } */ +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*\\\$bar," { target { ! ia32 } } } } */ diff --git a/gcc/testsuite/gcc.target/i386/pr67400-2.c b/gcc/testsuite/gcc.target/i386/pr67400-2.c new file mode 100644 index 0000000..9f3f4bc --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr67400-2.c @@ -0,0 +1,14 @@ +/* { dg-do compile { target *-*-linux* } } */ +/* { dg-options "-O2 -fno-pic -fno-plt" } */ + +extern void bar (void); +extern void *p; + +void +foo (void) +{ + p = &bar; +} + +/* { dg-final { scan-assembler "mov\(l|q\)\[ \t\]*bar@GOTPCREL" { target { ! ia32 } } } } */ +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*\\\$bar," { target { ! ia32 } } } } */ diff --git a/gcc/testsuite/gcc.target/i386/pr67400-3.c b/gcc/testsuite/gcc.target/i386/pr67400-3.c new file mode 100644 index 0000000..045974e --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr67400-3.c @@ -0,0 +1,16 @@ +/* { dg-do compile { target *-*-linux* } } */ +/* { dg-options "-O2 -fno-pic -fno-plt" } */ + +static void +bar (void) +{ +} + +void * +foo (void) +{ + return &bar; +} + +/* { dg-final { scan-assembler "mov\(l|q\)\[ \t\]*\\\$bar," } } */ +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*bar@GOTPCREL" { target { ! ia32 } } } } */ diff --git a/gcc/testsuite/gcc.target/i386/pr67400-4.c b/gcc/testsuite/gcc.target/i386/pr67400-4.c new file mode 100644 index 0000000..fd373db --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr67400-4.c @@ -0,0 +1,13 @@ +/* { dg-do compile { target *-*-linux* } } */ +/* { dg-options "-O2 -fno-pic -fno-plt" } */ + +extern void bar (void) __attribute__ ((visibility ("hidden"))); + +void * +foo (void) +{ + return &bar; +} + +/* { dg-final { scan-assembler "mov\(l|q\)\[ \t\]*\\\$bar," } } */ +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*bar@GOTPCREL" { target { ! ia32 } } } } */ diff --git a/gcc/testsuite/gcc.target/i386/pr67400-5.c b/gcc/testsuite/gcc.target/i386/pr67400-5.c new file mode 100644 index 0000000..9bb98dc --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr67400-5.c @@ -0,0 +1,11 @@ +/* { dg-do compile { target *-*-linux* } } */ +/* { dg-options "-O2 -fno-pic -fno-plt" } */ + +extern void foo (void); +extern void bar (int, int, int, int, int, int, void *); + +void +x (void) +{ + bar (1, 2, 3, 4, 5, 6, foo); +} diff --git a/gcc/testsuite/gcc.target/i386/pr67400-6.c b/gcc/testsuite/gcc.target/i386/pr67400-6.c new file mode 100644 index 0000000..b84196a --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr67400-6.c @@ -0,0 +1,13 @@ +/* { dg-do compile { target *-*-linux* } } */ +/* { dg-options "-O2 -fno-pic -fno-plt" } */ + +extern int bar (void); + +int +check (void *p) +{ + return p != &bar; +} + +/* { dg-final { scan-assembler "cmp\(l|q\)\[ \t\]*.*bar@GOTPCREL" { target { ! ia32 } } } } */ +/* { dg-final { scan-assembler-not "mov\(l|q\)\[ \t\]*\\\$bar," { target { ! ia32 } } } } */ -- 2.5.5
