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base: Fix undefined behavior in mask generation

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When generating a mask, if the number of bits is greater than
the maximum shift distance (63), the shift will have undefined
behavior. Previously the branch was taking care of a single
trespassing case, and it has been fixed to cover the remaining.

Issue-on: https://gem5.atlassian.net/browse/GEM5-205

Change-Id: Ib5a00917c8d2b23ffdb710c2f9673d956cd9f43e
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/27104
Tested-by: Gem5 Cloud Project GCB service account <345032938727@cloudbuild.gserviceaccount.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
This commit is contained in:
Daniel R. Carvalho
2020-03-26 11:29:11 +01:00
committed by Daniel Carvalho
parent 64134b6e66
commit ffad8a370a
1 changed files with 5 additions and 2 deletions
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7
src/base/bitfield.hh
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@@ -50,12 +50,15 @@
extern const uint8_t reverseLookUpTable[];
/**
* Generate a 64-bit mask of 'nbits' 1s, right justified.
* Generate a 64-bit mask of 'nbits' 1s, right justified. If a number of bits
* greater than 64 is given, it is truncated to 64.
*
* @param nbits The number of bits set in the mask.
*/
inline uint64_t
mask(int nbits)
{
return (nbits == 64) ? (uint64_t)-1LL : (1ULL << nbits) - 1;
return (nbits >= 64) ? (uint64_t)-1LL : (1ULL << nbits) - 1;
}
/**