include/asm-generic/div64.h:164 (null)() warn: right shifting more than type allows 32 vs 32

BCC: [email protected]
CC: [email protected]
CC: [email protected]
TO: Christoph Hellwig <[email protected]>
CC: Andrew Morton <[email protected]>
CC: Linux Memory Management List <[email protected]>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   8ba098e6b6ff0db8edf28528d1552be261af30d4
commit: 769d603fc44f896e7f61de7f0cdb8b78d46bc8c8 raid6: hide internals
date:   9 weeks ago
:::::: branch date: 34 hours ago
:::::: commit date: 9 weeks ago
config: powerpc-randconfig-r073-20260801 (https://download.01.org/0day-ci/archive/20260801/[email protected]/config)
compiler: powerpc-linux-gcc (GCC) 8.5.0
smatch: v0.5.0-9187-g5189e3fb

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Fixes: 769d603fc44f ("raid6: hide internals")
| Reported-by: kernel test robot <[email protected]>
| Reported-by: Dan Carpenter <[email protected]>
| Closes: https://lore.kernel.org/r/[email protected]/

smatch warnings:
include/asm-generic/div64.h:164 (null)() warn: right shifting more than type allows 32 vs 32

vim +164 include/asm-generic/div64.h

461a5e51060c93 Nicolas Pitre 2015-10-30  125  
f682b27c57aec2 Nicolas Pitre 2015-10-30  126  #ifndef __arch_xprod_64
f682b27c57aec2 Nicolas Pitre 2015-10-30  127  /*
f682b27c57aec2 Nicolas Pitre 2015-10-30  128   * Default C implementation for __arch_xprod_64()
f682b27c57aec2 Nicolas Pitre 2015-10-30  129   *
f682b27c57aec2 Nicolas Pitre 2015-10-30  130   * Prototype: uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
f682b27c57aec2 Nicolas Pitre 2015-10-30  131   * Semantic:  retval = ((bias ? m : 0) + m * n) >> 64
f682b27c57aec2 Nicolas Pitre 2015-10-30  132   *
f682b27c57aec2 Nicolas Pitre 2015-10-30  133   * The product is a 128-bit value, scaled down to 64 bits.
00a31dd3acea0f Nicolas Pitre 2024-10-03  134   * Hoping for compile-time optimization of  conditional code.
f682b27c57aec2 Nicolas Pitre 2015-10-30  135   * Architectures may provide their own optimized assembly implementation.
f682b27c57aec2 Nicolas Pitre 2015-10-30  136   */
d533cb2d2af400 Nicolas Pitre 2024-10-03  137  #ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
d533cb2d2af400 Nicolas Pitre 2024-10-03  138  static __always_inline
d533cb2d2af400 Nicolas Pitre 2024-10-03  139  #else
d533cb2d2af400 Nicolas Pitre 2024-10-03  140  static inline
d533cb2d2af400 Nicolas Pitre 2024-10-03  141  #endif
d533cb2d2af400 Nicolas Pitre 2024-10-03  142  uint64_t __arch_xprod_64(const uint64_t m, uint64_t n, bool bias)
f682b27c57aec2 Nicolas Pitre 2015-10-30  143  {
f682b27c57aec2 Nicolas Pitre 2015-10-30  144  	uint32_t m_lo = m;
f682b27c57aec2 Nicolas Pitre 2015-10-30  145  	uint32_t m_hi = m >> 32;
f682b27c57aec2 Nicolas Pitre 2015-10-30  146  	uint32_t n_lo = n;
f682b27c57aec2 Nicolas Pitre 2015-10-30  147  	uint32_t n_hi = n >> 32;
00a31dd3acea0f Nicolas Pitre 2024-10-03  148  	uint64_t x, y;
f682b27c57aec2 Nicolas Pitre 2015-10-30  149  
00a31dd3acea0f Nicolas Pitre 2024-10-03  150  	/* Determine if overflow handling can be dispensed with. */
00a31dd3acea0f Nicolas Pitre 2024-10-03  151  	bool no_ovf = __builtin_constant_p(m) &&
00a31dd3acea0f Nicolas Pitre 2024-10-03  152  		      ((m >> 32) + (m & 0xffffffff) < 0x100000000);
f682b27c57aec2 Nicolas Pitre 2015-10-30  153  
00a31dd3acea0f Nicolas Pitre 2024-10-03  154  	if (no_ovf) {
00a31dd3acea0f Nicolas Pitre 2024-10-03  155  		x = (uint64_t)m_lo * n_lo + (bias ? m : 0);
00a31dd3acea0f Nicolas Pitre 2024-10-03  156  		x >>= 32;
00a31dd3acea0f Nicolas Pitre 2024-10-03  157  		x += (uint64_t)m_lo * n_hi;
00a31dd3acea0f Nicolas Pitre 2024-10-03  158  		x += (uint64_t)m_hi * n_lo;
00a31dd3acea0f Nicolas Pitre 2024-10-03  159  		x >>= 32;
00a31dd3acea0f Nicolas Pitre 2024-10-03  160  		x += (uint64_t)m_hi * n_hi;
f682b27c57aec2 Nicolas Pitre 2015-10-30  161  	} else {
00a31dd3acea0f Nicolas Pitre 2024-10-03  162  		x = (uint64_t)m_lo * n_lo + (bias ? m_lo : 0);
00a31dd3acea0f Nicolas Pitre 2024-10-03  163  		y = (uint64_t)m_lo * n_hi + (uint32_t)(x >> 32) + (bias ? m_hi : 0);
00a31dd3acea0f Nicolas Pitre 2024-10-03 @164  		x = (uint64_t)m_hi * n_hi + (uint32_t)(y >> 32);
00a31dd3acea0f Nicolas Pitre 2024-10-03  165  		y = (uint64_t)m_hi * n_lo + (uint32_t)y;
00a31dd3acea0f Nicolas Pitre 2024-10-03  166  		x += (uint32_t)(y >> 32);
f682b27c57aec2 Nicolas Pitre 2015-10-30  167  	}
f682b27c57aec2 Nicolas Pitre 2015-10-30  168  
00a31dd3acea0f Nicolas Pitre 2024-10-03  169  	return x;
f682b27c57aec2 Nicolas Pitre 2015-10-30  170  }
f682b27c57aec2 Nicolas Pitre 2015-10-30  171  #endif
f682b27c57aec2 Nicolas Pitre 2015-10-30  172  

:::::: The code at line 164 was first introduced by commit
:::::: 00a31dd3acea0f88f947fc71e268ebb34b59f218 asm-generic/div64: optimize/simplify __div64_const32()

:::::: TO: Nicolas Pitre <[email protected]>
:::::: CC: Arnd Bergmann <[email protected]>

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