[IndVarSimplify] Cherry-pick IndVarSimplify hoisting trap checks out of loop. #12059
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…cal writes (llvm#155901) This is important to optimize patterns that frequently appear with bounds checks: ``` for (int i = 0; i < N; ++i) { bar[i] = foo[i] + 123; } ``` which gets roughly turned into ``` for (int i = 0; i < N; ++i) { if (i >= size of foo) ubsan.trap(); if (i >= size of bar) ubsan.trap(); bar[i] = foo[i] + 123; } ``` Motivating example: https://github.com/google/boringssl/blob/main/crypto/fipsmodule/hmac/hmac.cc.inc#L138 I hand-verified the assembly and confirmed that this optimization removes the check in the loop. This also allowed the loop to be vectorized. Alive2: https://alive2.llvm.org/ce/z/3qMdLF I did a `stage2-check-all` for both normal and `-DBOOTSTRAP_CMAKE_C[XX]_FLAGS="-fsanitize=array-bounds -fsanitize-trap=all"`. I also ran some Google-internal tests with `fsanitize=array-bounds`. Everything passes. (cherry picked from commit 39b0cbe) Conflicts: llvm/test/Transforms/IndVarSimplify/X86/overflow-intrinsics.ll rdar://162704645
aemerson
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Jan 5, 2026
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AbhayKanhere
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cherry-pick trap checks out of the loop patch from upstream.
rdar://162704645