currently, aarch64 LEGITIMIZE_ADDRESS_P hook will reject all "reg + offset" address given "offset" is beyond supported range.
while this may be too strict. we should honor the "strict_p" parameter in the hook. before reload, we accept all offset if it's a frame access, because the offset may change during later register elimination. the early reject of "reg + offset" may cause extra registers created, and if that register live range is across function invoking then callee saved reg needed, thus introduce extra reg save/restore also. give a simple example as: int test15 (void) { unsigned char a[480]; initialize_array (a, 480); if (a[0] == 0x10) return 1; return 0; } .S before the patch (-O2 -fPIC) === test15: sub sp, sp, #480 mov w1, 480 stp x29, x30, [sp, -32]! add x29, sp, 0 str x19, [sp, 16] add x19, x29, 32 mov x0, x19 bl initialize_array ldrb w0, [x19] ldr x19, [sp, 16] ldp x29, x30, [sp], 32 cmp w0, 16 cset w0, eq add sp, sp, 480 ret .S after the patch === test15: stp x29, x30, [sp, -496]! mov w1, 480 add x29, sp, 0 add x0, x29, 16 bl initialize_array ldrb w0, [x29, 16] ldp x29, x30, [sp], 496 cmp w0, 16 cset w0, eq ret test done ========= no regression on aarch64-none-elf bare metal. bootstrap OK on aarch64. OK for trunk? thanks. gcc/ * config/aarch64/aarch64.c (aarch64_classify_address): Accept all offset for frame access when strict_p is false. gcc/testsuite * gcc.target/aarch64/legitimize_stack_var_before_reload_1.c: New testcase.
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c index ed80269..c8e5808 100644 --- a/gcc/config/aarch64/aarch64.c +++ b/gcc/config/aarch64/aarch64.c @@ -3248,6 +3248,21 @@ aarch64_classify_address (struct aarch64_address_info *info, case PLUS: op0 = XEXP (x, 0); op1 = XEXP (x, 1); + + if (! strict_p + && GET_CODE (op0) == REG + && (op0 == virtual_stack_vars_rtx + || op0 == frame_pointer_rtx + || op0 == arg_pointer_rtx) + && GET_CODE (op1) == CONST_INT) + { + info->type = ADDRESS_REG_IMM; + info->base = op0; + info->offset = op1; + + return true; + } + if (GET_MODE_SIZE (mode) != 0 && CONST_INT_P (op1) && aarch64_base_register_rtx_p (op0, strict_p)) diff --git a/gcc/testsuite/gcc.target/aarch64/legitimize_stack_var_before_reload_1.c b/gcc/testsuite/gcc.target/aarch64/legitimize_stack_var_before_reload_1.c new file mode 100644 index 0000000..e5f0bd1 --- /dev/null +++ b/gcc/testsuite/gcc.target/aarch64/legitimize_stack_var_before_reload_1.c @@ -0,0 +1,21 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-rtl-expand" } */ + +extern void initialize_array (unsigned char *, int); + +int +test15 (void) +{ + unsigned char a[480]; + + initialize_array (a, 480); + + if (a[0] == 0x10) + return 1; + + return 0; +} + +/* { dg-final { scan-rtl-dump "mem/j/c:QI \\(plus:DI" "expand" } } */ + +/* { dg-final { cleanup-rtl-dump "expand" } } */