Decouple interrupt bit index calculation from ilog2 #44
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ilog2 is a common function, but interrupt bit index calculation is application dependent. Thus, decouple them and create a new macro called GET_INTR_IDX which leverages the ilog2 to calculate the interrupt bit index.
jserv
reviewed
May 16, 2024
| @@ -14,9 +14,20 @@ | |||
| /* Ensure that __builtin_clz is never called with 0 argument */ | |||
| static inline int ilog2(int x) | |||
| { | |||
| return 31 - __builtin_clz(x | 1); | |||
| return __builtin_clz(x | 1); | |||
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floor(log2(x)) should be 31 - __builtin_clz(x | 1).
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floor(log2(x)) should be
31 - __builtin_clz(x | 1).
31 - __builtin_clz(x | 1) seems like a calculation of first bit set index in a 32-bit number instead of floor(log2(x)) ?
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Check this: https://github.com/apple/swift-llbuild/blob/main/include/llvm/Support/MathExtras.h#L536-L541
Seems like I had misunderstood it. I will close this PR.
jserv
reviewed
May 16, 2024
| * GET_INTR_IDX(4) = 2 | ||
| * GET_INTR_IDX(8) = 3 | ||
| */ | ||
| #define GET_INTR_IDX(x) (31 - ilog2(x)) |
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The naming is confusing. Refine it.
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ilog2 is a common function, but interrupt bit index calculation is application dependent. Thus, decouple them and create a new macro called GET_INTR_IDX which leverages the ilog2 to calculate the interrupt bit index.