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Fix heap when size_t is not unsigned long long

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When the width of size_t doesn't match the width of the unsigned long
long type, the number of leading zeros doesn't match, making the
heap_get_move() function return incorrect values. This is the case on
ARMv7 with 32 bits, where size_t is 32 bits but unsigned long long is 64
bits.

We check the size of size_t to select which builtin we need. The sizeof
operator cannot be used at preprocessing, so we rely on the
optimizations to only leave the proper assembly instruction.

Fixes: https://pm.bsc.es/gitlab/rarias/ovni/-/issues/193
This commit is contained in:
Rodrigo Arias 2024-06-21 16:58:04 +02:00 committed by Rodrigo Arias
parent 91e8367d35
commit 3d8c84e17c
1 changed files with 17 additions and 3 deletions
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20
src/include/heap.h
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@ -1,4 +1,4 @@
/* Copyright (c) 2021-2023 Barcelona Supercomputing Center (BSC)
/* Copyright (c) 2021-2024 Barcelona Supercomputing Center (BSC)
* SPDX-License-Identifier: GPL-3.0-or-later */
/* Author: David Alvarez
@ -112,6 +112,20 @@ heap_max(heap_head_t *head)
return head->root;
}
static inline int
leading_zeros(size_t x)
{
/* Call and if()'s optimized by the compiler with -O2 */
if (sizeof(size_t) == sizeof(unsigned int))
return __builtin_clz(x);
else if (sizeof(size_t) == sizeof(unsigned long))
return __builtin_clzl(x);
else if (sizeof(size_t) == sizeof(unsigned long long))
return __builtin_clzll(x);
else
die("cannot find suitable size for __builtin_clz*");
}
/* Get a move to reach a leaf */
static inline int
heap_get_move(size_t *node /*out*/)
@ -119,8 +133,8 @@ heap_get_move(size_t *node /*out*/)
size_t aux_node = *node;
// Round to previous po2
size_t base = (1ULL) << (sizeof(size_t) * 8
- __builtin_clzll(aux_node) - 1);
int shift = sizeof(size_t) * 8 - leading_zeros(aux_node) - 1;
size_t base = 1ULL << shift;
aux_node -= base / 2;