| Message ID | CAFULd4Z090BxR8PVxLmJwRb3494EWoVE1+apSYdKoVk-vJPx3A@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC] i386: Do not emit segment overrides for %p and %P [PR100936] | expand |
On Tue, Jun 8, 2021 at 5:46 PM Uros Bizjak <ubizjak@gmail.com> wrote: > > Using %p to move the address of a symbol using LEA: > > asm ("lea %p1, %0" : "=r"(addr) : "m"(var)); > > emits assembler warning when VAR is declared in a non-generic address space: > > Warning: segment override on `lea' is ineffectual > > The problem is with %p operand modifier, which should emit raw symbol name: > > p -- print raw symbol name. > > Similar problem exists with %P modifier, trying to CALL or JMP to an > overridden symbol,e.g: > > call %gs:zzz > jmp %gs:zzz > > emits assembler warning: > > Warning: skipping prefixes on `call' > Warning: skipping prefixes on `jmp' > > Ensure that %p and %P never emit segment overrides. > > 2021-06-08 Uroš Bizjak <ubizjak@gmail.com> > > gcc/ > PR target/100936 > * config/i386/i386.c (print_operand_address_as): Rename "no_rip" > argument to "raw". Do not emit segment overrides when "raw" is true. > > gcc/testsuite/ > > PR target/100936 > * gcc.target/i386/pr100936.c: New test. > > Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}. Now pushed to master. Uros.
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c index b0d19a61a76..05b8dc806cd 100644 --- a/gcc/config/i386/i386.c +++ b/gcc/config/i386/i386.c @@ -13531,7 +13531,7 @@ ix86_print_operand_punct_valid_p (unsigned char code) static void ix86_print_operand_address_as (FILE *file, rtx addr, - addr_space_t as, bool no_rip) + addr_space_t as, bool raw) { struct ix86_address parts; rtx base, index, disp; @@ -13570,7 +13570,7 @@ ix86_print_operand_address_as (FILE *file, rtx addr, else gcc_assert (ADDR_SPACE_GENERIC_P (parts.seg)); - if (!ADDR_SPACE_GENERIC_P (as)) + if (!ADDR_SPACE_GENERIC_P (as) && !raw) { if (ASSEMBLER_DIALECT == ASM_ATT) putc ('%', file); @@ -13589,7 +13589,7 @@ ix86_print_operand_address_as (FILE *file, rtx addr, } /* Use one byte shorter RIP relative addressing for 64bit mode. */ - if (TARGET_64BIT && !base && !index && !no_rip) + if (TARGET_64BIT && !base && !index && !raw) { rtx symbol = disp; diff --git a/gcc/testsuite/gcc.target/i386/pr100936.c b/gcc/testsuite/gcc.target/i386/pr100936.c new file mode 100644 index 00000000000..c076cbb2405 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr100936.c @@ -0,0 +1,34 @@ +/* PR target/100936 */ +/* { dg-do assemble } */ +/* { dg-options "-O2" } */ + +__seg_gs int var; + +static int +*foo (void) +{ + int *addr; + + asm ("lea %p1, %0" : "=r"(addr) : "m"(var)); + + return addr; +} + +static int +bar (int *addr) +{ + int val; + + asm ("mov %%gs:%1, %0" : "=r"(val) : "m"(*addr)); + + return val; +} + +int +baz (void) +{ + int *addr = foo(); + int val = bar (addr); + + return val; +}
Using %p to move the address of a symbol using LEA: asm ("lea %p1, %0" : "=r"(addr) : "m"(var)); emits assembler warning when VAR is declared in a non-generic address space: Warning: segment override on `lea' is ineffectual The problem is with %p operand modifier, which should emit raw symbol name: p -- print raw symbol name. Similar problem exists with %P modifier, trying to CALL or JMP to an overridden symbol,e.g: call %gs:zzz jmp %gs:zzz emits assembler warning: Warning: skipping prefixes on `call' Warning: skipping prefixes on `jmp' Ensure that %p and %P never emit segment overrides. 2021-06-08 Uroš Bizjak <ubizjak@gmail.com> gcc/ PR target/100936 * config/i386/i386.c (print_operand_address_as): Rename "no_rip" argument to "raw". Do not emit segment overrides when "raw" is true. gcc/testsuite/ PR target/100936 * gcc.target/i386/pr100936.c: New test. Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}. Uros.