[ir] [transforms] Added assertion that indices won't cause overflow under debug mode #2199
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…rflow under debug mode. Fixed one typo in write_test docs.
k-ye
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k-ye
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Mar 3, 2021
taichi/transforms/simplify.cpp
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| auto zero = Stmt::make<ConstStmt>(LaneAttribute<TypedConstant>(0)); | ||
| auto check_sum = Stmt::make<BinaryOpStmt>(BinaryOpType::cmp_ge, sum.get(), zero.get()); | ||
| auto assert = Stmt::make<AssertStmt>(check_sum.get(), "The indices provided are too big!", std::vector<Stmt *>()); | ||
| auto select = Stmt::make<TernaryOpStmt>(TernaryOpType::select, check_sum.get(), sum.get(), zero.get()); |
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Let's add this comment to explain why we need select:
Because Taichi's assertion is checked only after the execution of the whole kernel, when the linear index overflows and goes negative, we have to replace that with 0 to make sure that the rest of the kernel can still complete. Otherwise, Taichi would crash due to the illegal memory address.
Co-authored-by: Ye Kuang <k-ye@users.noreply.github.com>
k-ye
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This was referenced Mar 14, 2021
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Related issue = #2146
With large indices such as variable[300][300][300][300], when performing IR transform and simplifying this to an integer, this integer will overflow to negative number, which would cause SegFault. I added assertion to IR under debug mode which would assert that the simplified index must NOT be less than 0. One test is provided named "test_indices_assert.py".
For modification in docs, there is one typo that added an 's' after 'exclude'. I simply deleted this 's'.
@k-ye
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