[PATCH] D83595: [Draft][MSAN] Optimize away poisoning allocas that are always written before load

[Gui Andrade via Phabricator via llvm-commits]

guiand added a comment.

This actually has very significant effects on some, but not all, benchmarks.

Running `grep` I observed ~8% decrease in binary with this patch. But `clang` sees little effect: <1%.

On a few different benchmarks from a benchmark suite, this also decreased runtime overhead by a significant amount: 8% for sha512 <https://github.com/rv8-io/rv8-bench/blob/master/src/sha512.c>, and 13% for qsort <https://github.com/rv8-io/rv8-bench/blob/master/src/qsort.c>.


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https://reviews.llvm.org/D83595