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From: Uros Bizjak <uros@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r12-1318] i386: Do not emit segment overrides for %p and %P [PR100936] Date: Wed, 9 Jun 2021 07:46:53 +0000 (GMT) [thread overview] Message-ID: <20210609074653.80F44385802A@sourceware.org> (raw) https://gcc.gnu.org/g:267dbd42f42c52a515f49c0875d296a9cf5988fe commit r12-1318-g267dbd42f42c52a515f49c0875d296a9cf5988fe Author: Uros Bizjak <ubizjak@gmail.com> Date: Wed Jun 9 09:46:00 2021 +0200 i386: Do not emit segment overrides for %p and %P [PR100936] 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. Diff: --- gcc/config/i386/i386.c | 6 +++--- gcc/testsuite/gcc.target/i386/pr100936.c | 34 ++++++++++++++++++++++++++++++++ 2 files changed, 37 insertions(+), 3 deletions(-) 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; +}
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