From 5ee31e57d2fe70a7847dae2a3df0f19e3875fd97 Mon Sep 17 00:00:00 2001 From: Richard Sandiford Date: Tue, 26 Jan 2016 09:53:33 +0000 Subject: [PATCH] PR 69400: Invalid 128-bit modulus result As described in the PR, wi::divmod_internal was sign- rather than zero-extending a modulus result in cases where the result has fewer HWIs than the precision and the upper bit of the upper HWI was set. This patch tries to make things more robust by getting wi_pack to handle the canonicalisation step itself. Tested on x86_64-linux-gnu. I added tests to the wide-int plugin since that seemed more direct. gcc/ PR tree-optimization/69400 * wide-int.cc (wi_pack): Take the precision as argument and perform canonicalization here rather than in the callers. Use the main loop to handle all full-width HWIs. Add a zero HWI if in_len isn't a full result. (wi::divmod_internal): Update accordingly. (wi::mul_internal): Likewise. Simplify. gcc/testsuite/ PR tree-optimization/69400 * gcc.dg/plugin/wide-int_plugin.c (test_wide_int_mod_trunc): New function. (plugin_init): Call it. * gcc.dg/torture/pr69400.c: New test. From-SVN: r232817 --- gcc/ChangeLog | 10 ++++ gcc/testsuite/ChangeLog | 8 +++ gcc/testsuite/gcc.dg/plugin/wide-int_plugin.c | 33 +++++++++++++ gcc/testsuite/gcc.dg/torture/pr69400.c | 20 ++++++++ gcc/wide-int.cc | 49 +++++++------------ 5 files changed, 90 insertions(+), 30 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/torture/pr69400.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 9f124dcb59f..7a4e57bddbd 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,13 @@ +2016-01-26 Richard Sandiford + + PR tree-optimization/69400 + * wide-int.cc (wi_pack): Take the precision as argument and + perform canonicalization here rather than in the callers. + Use the main loop to handle all full-width HWIs. Add a + zero HWI if in_len isn't a full result. + (wi::divmod_internal): Update accordingly. + (wi::mul_internal): Likewise. Simplify. + 2016-01-25 Aditya Kumar Sebastian Pop diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 5c5d28a951f..ffb4314b9e6 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,11 @@ +2016-01-26 Richard Sandiford + + PR tree-optimization/69400 + * gcc.dg/plugin/wide-int_plugin.c (test_wide_int_mod_trunc): New + function. + (plugin_init): Call it. + * gcc.dg/torture/pr69400.c: New test. + 2016-01-26 Christophe Lyon * gcc.target/arm/pr68674.c: Check and use arm_fp effective target. diff --git a/gcc/testsuite/gcc.dg/plugin/wide-int_plugin.c b/gcc/testsuite/gcc.dg/plugin/wide-int_plugin.c index 17604c8cf99..eea56be5e7c 100644 --- a/gcc/testsuite/gcc.dg/plugin/wide-int_plugin.c +++ b/gcc/testsuite/gcc.dg/plugin/wide-int_plugin.c @@ -36,11 +36,44 @@ test_wide_int_round_sdiv (void) abort (); } +static void +test_wide_int_mod_trunc (void) +{ + for (unsigned int i = 1; i < MAX_BITSIZE_MODE_ANY_INT; ++i) + { + if (wi::smod_trunc (wi::lshift (1, i + 1) - 3, + wi::lshift (1, i) - 1) + != wi::lshift (1, i) - 2) + abort (); + for (unsigned int base = 32; base <= MAX_BITSIZE_MODE_ANY_INT; base *= 2) + for (int bias = -1; bias <= 1; ++bias) + { + unsigned int precision = base + bias; + if (i + 1 < precision && precision <= MAX_BITSIZE_MODE_ANY_INT) + { + wide_int one = wi::uhwi (1, precision); + wide_int a = wi::lshift (one, i + 1) - 3; + wide_int b = wi::lshift (one, i) - 1; + wide_int c = wi::lshift (one, i) - 2; + if (wi::umod_trunc (a, b) != c) + abort (); + if (wi::smod_trunc (a, b) != c) + abort (); + if (wi::smod_trunc (-a, b) != -c) + abort (); + if (wi::smod_trunc (a, -b) != c) + abort (); + } + } + } +} + int plugin_init (struct plugin_name_args *plugin_info, struct plugin_gcc_version *version) { test_double_int_round_udiv (); test_wide_int_round_sdiv (); + test_wide_int_mod_trunc (); return 0; } diff --git a/gcc/testsuite/gcc.dg/torture/pr69400.c b/gcc/testsuite/gcc.dg/torture/pr69400.c new file mode 100644 index 00000000000..e0eb521244d --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr69400.c @@ -0,0 +1,20 @@ +/* { dg-do run { target int128 } } */ + +typedef unsigned __int128 u128; + +u128 __attribute__((noinline, noclone)) +foo(void) +{ + u128 u = -2; + u %= 0xffffffffffffffffllu; + return u; +} + +int +main() +{ + u128 x = foo(); + if (x != 0xfffffffffffffffellu) + __builtin_abort(); + return 0; +} diff --git a/gcc/wide-int.cc b/gcc/wide-int.cc index 35eee2c3bc9..195ac26fa56 100644 --- a/gcc/wide-int.cc +++ b/gcc/wide-int.cc @@ -1214,30 +1214,32 @@ wi_unpack (unsigned HOST_HALF_WIDE_INT *result, const HOST_WIDE_INT *input, result[j++] = mask; } -/* The inverse of wi_unpack. IN_LEN is the the number of input - blocks. The number of output blocks will be half this amount. */ -static void -wi_pack (unsigned HOST_WIDE_INT *result, +/* The inverse of wi_unpack. IN_LEN is the number of input + blocks and PRECISION is the precision of the result. Return the + number of blocks in the canonicalized result. */ +static unsigned int +wi_pack (HOST_WIDE_INT *result, const unsigned HOST_HALF_WIDE_INT *input, - unsigned int in_len) + unsigned int in_len, unsigned int precision) { unsigned int i = 0; unsigned int j = 0; + unsigned int blocks_needed = BLOCKS_NEEDED (precision); - while (i + 2 < in_len) + while (i + 1 < in_len) { - result[j++] = (unsigned HOST_WIDE_INT)input[i] - | ((unsigned HOST_WIDE_INT)input[i + 1] - << HOST_BITS_PER_HALF_WIDE_INT); + result[j++] = ((unsigned HOST_WIDE_INT) input[i] + | ((unsigned HOST_WIDE_INT) input[i + 1] + << HOST_BITS_PER_HALF_WIDE_INT)); i += 2; } /* Handle the case where in_len is odd. For this we zero extend. */ if (in_len & 1) - result[j++] = (unsigned HOST_WIDE_INT)input[i]; - else - result[j++] = (unsigned HOST_WIDE_INT)input[i] - | ((unsigned HOST_WIDE_INT)input[i + 1] << HOST_BITS_PER_HALF_WIDE_INT); + result[j++] = (unsigned HOST_WIDE_INT) input[i]; + else if (j < blocks_needed) + result[j++] = 0; + return canonize (result, j, precision); } /* Multiply Op1 by Op2. If HIGH is set, only the upper half of the @@ -1460,19 +1462,8 @@ wi::mul_internal (HOST_WIDE_INT *val, const HOST_WIDE_INT *op1val, *overflow = true; } - if (high) - { - /* compute [prec] <- ([prec] * [prec]) >> [prec] */ - wi_pack ((unsigned HOST_WIDE_INT *) val, - &r[half_blocks_needed], half_blocks_needed); - return canonize (val, blocks_needed, prec); - } - else - { - /* compute [prec] <- ([prec] * [prec]) && ((1 << [prec]) - 1) */ - wi_pack ((unsigned HOST_WIDE_INT *) val, r, half_blocks_needed); - return canonize (val, blocks_needed, prec); - } + int r_offset = high ? half_blocks_needed : 0; + return wi_pack (val, &r[r_offset], half_blocks_needed, prec); } /* Compute the population count of X. */ @@ -1847,8 +1838,7 @@ wi::divmod_internal (HOST_WIDE_INT *quotient, unsigned int *remainder_len, unsigned int quotient_len = 0; if (quotient) { - wi_pack ((unsigned HOST_WIDE_INT *) quotient, b_quotient, m); - quotient_len = canonize (quotient, (m + 1) / 2, dividend_prec); + quotient_len = wi_pack (quotient, b_quotient, m, dividend_prec); /* The quotient is neg if exactly one of the divisor or dividend is neg. */ if (dividend_neg != divisor_neg) @@ -1859,8 +1849,7 @@ wi::divmod_internal (HOST_WIDE_INT *quotient, unsigned int *remainder_len, if (remainder) { - wi_pack ((unsigned HOST_WIDE_INT *) remainder, b_remainder, n); - *remainder_len = canonize (remainder, (n + 1) / 2, dividend_prec); + *remainder_len = wi_pack (remainder, b_remainder, n, dividend_prec); /* The remainder is always the same sign as the dividend. */ if (dividend_neg) *remainder_len = wi::sub_large (remainder, zeros, 1, remainder, -- 2.30.2