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[Backport llvm-project#97148][AArch64] Avoid overflow when using shl lower mul #174

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merged 1 commit into from
Jun 30, 2024
Merged

[Backport llvm-project#97148][AArch64] Avoid overflow when using shl lower mul #174

merged 1 commit into from
Jun 30, 2024

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@DianQK DianQK commented Jun 30, 2024 •
edited by nikic
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@DianQK
[AArch64] Avoid overflow when using shl lower mul (llvm#97148)
9817e85 
Fixes llvm#97147.

Transforming `(mul x, -(2^(N-M) - 1) * 2^M)` to `(sub (shl x, M), (shl
x, N))` will cause overflow when N is 32 and M is 31. I still added
checks for all scenarios, even other scenarios, don't seem to cause overflow.

(cherry picked from commit 4a96803)
@DianQK DianQK requested a review from a team June 30, 2024 14:16
@nikic nikic merged commit 934954a into rust-lang:rustc/18.1-2024-05-19 Jun 30, 2024
@DianQK DianQK deleted the backport-97148 branch June 30, 2024 21:50
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