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genmodes: Update GET_MODE_MASK when changing NUNITS [PR98214]

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The static GET_MODE_MASKs for SVE vectors are based on the
static precisions, which in turn are based on 128-bit SVE.
The precisions are later updated based on -msve-vector-bits
(usually to become variable length), but the GET_MODE_MASK
stayed the same.  This caused combine to fold:

  (*_extract:DI (subreg:DI (reg:VNxMM R) 0) ...)

to zero because the extracted bits appeared to be insignificant.

gcc/
	PR rtl-optimization/98214
	* genmodes.c (emit_insn_modes_h): Emit a definition of CONST_MODE_MASK.
	(emit_mode_mask): Treat mode_mask_array as non-constant if adj_nunits.
	(emit_mode_adjustments): Update GET_MODE_MASK when updating
	GET_MODE_NUNITS.
	* machmode.h (mode_mask_array): Use CONST_MODE_MASK.
This commit is contained in:
Richard Sandiford 2020-12-31 16:10:47 +00:00
parent d2eb616a0f
commit 0411210fdd
3 changed files with 42 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
gcc/genmodes.c
View File

@ -1324,6 +1324,7 @@ enum machine_mode\n{");
#endif
printf ("#define CONST_MODE_IBIT%s\n", adj_ibit ? "" : " const");
printf ("#define CONST_MODE_FBIT%s\n", adj_fbit ? "" : " const");
printf ("#define CONST_MODE_MASK%s\n", adj_nunits ? "" : " const");
emit_max_int ();
for_all_modes (c, m)
@ -1561,8 +1562,8 @@ emit_mode_mask (void)
int c;
struct mode_data *m;
print_decl ("unsigned HOST_WIDE_INT", "mode_mask_array",
"NUM_MACHINE_MODES");
print_maybe_const_decl ("%sunsigned HOST_WIDE_INT", "mode_mask_array",
"NUM_MACHINE_MODES", adj_nunits);
puts ("\
#define MODE_MASK(m) \\\n\
((m) >= HOST_BITS_PER_WIDE_INT) \\\n\
@ -1719,6 +1720,20 @@ emit_mode_adjustments (void)
struct mode_adjust *a;
struct mode_data *m;
if (adj_nunits)
printf ("\n"
"void\n"
"adjust_mode_mask (machine_mode mode)\n"
"{\n"
" unsigned int precision;\n"
" if (GET_MODE_PRECISION (mode).is_constant (&precision)\n"
" && precision < HOST_BITS_PER_WIDE_INT)\n"
" mode_mask_array[mode] = (HOST_WIDE_INT_1U << precision) - 1;"
"\n"
" else\n"
" mode_mask_array[mode] = HOST_WIDE_INT_M1U;\n"
"}\n");
puts ("\
\nvoid\
\ninit_adjust_machine_modes (void)\
@ -1736,10 +1751,11 @@ emit_mode_adjustments (void)
printf (" int old_factor = vector_element_size"
" (mode_precision[E_%smode], mode_nunits[E_%smode]);\n",
m->name, m->name);
printf (" mode_precision[E_%smode] = ps * old_factor;\n", m->name);
printf (" mode_precision[E_%smode] = ps * old_factor;\n", m->name);
printf (" mode_size[E_%smode] = exact_div (mode_precision[E_%smode],"
" BITS_PER_UNIT);\n", m->name, m->name);
printf (" mode_nunits[E_%smode] = ps;\n", m->name);
printf (" adjust_mode_mask (E_%smode);\n", m->name);
printf (" }\n");
}

3
gcc/machmode.h
View File

@ -712,7 +712,8 @@ extern CONST_MODE_FBIT unsigned char mode_fbit[NUM_MACHINE_MODES];
/* Get a bitmask containing 1 for all bits in a word
that fit within mode MODE. */
extern const unsigned HOST_WIDE_INT mode_mask_array[NUM_MACHINE_MODES];
extern CONST_MODE_MASK unsigned HOST_WIDE_INT
mode_mask_array[NUM_MACHINE_MODES];
#define GET_MODE_MASK(MODE) mode_mask_array[MODE]

21
gcc/testsuite/gcc.target/aarch64/sve/pr98214.c Normal file
View File

@ -0,0 +1,21 @@
/* { dg-options "-O3 -msve-vector-bits=512" } */
long c;
int a;
int e[14];
short b[14];
void d(long *f, long h) { *f ^= h + *f; }
void this_test_has_completed_successfully ();
int main() {
e[2] = 1;
for (int g = 0; g < 13; g++)
a = b[g] = e[g];
d(&c, a);
for (int g = 0; g < 4; g++)
d(&c, b[2]);
if (c != 15)
__builtin_abort();
this_test_has_completed_successfully ();
}
/* { dg-final { scan-assembler {this_test_has_completed_successfully} } } */