[PATCH] D40048: [asan] Prevent rematerialization of &__asan_shadow.

[Evgenii Stepanov via Phabricator via llvm-commits]

eugenis created this revision.
Herald added subscribers: hiraditya, kristof.beyls, aemerson.

In the mode when ASan shadow base is computed as the address of an
external global (__asan_shadow, currently on android/arm32 only),
regalloc prefers to rematerialize this value to save register spills.
Even in -Os. On arm32 it is rather expensive (2 loads + 1 constant
pool entry).

This changes adds an inline asm in the function prologue to suppress
this behavior. It reduces AsanTest binary size by 7%.


https://reviews.llvm.org/D40048

Files:
  llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
  llvm/test/Instrumentation/AddressSanitizer/with-ifunc.ll

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