[llvm-dev] [RFC][ARM] -Oz implies -mthumb

Sjoerd Meijer via llvm-dev llvm-dev at lists.llvm.org
Thu Nov 15 03:49:43 PST 2018


I would like to address an issue/inconsistency related to command line options and compiling for minimum code size, and wanted to check if there would be any problems or objections to my change.

The problem is that compiling for minimum code size like this:

    -Oz --target=arm-arm--eabi -mcpu=cortex-xyz

does not really give minimum code size because -mthumb is not enabled. This looks like a sub-optimal user experience to me, and also, it is inconsistent with GCC's behaviour.

In other words: for AArch32, optimisation level -Oz targets A32, but I would like to change that to T32, and so I would like to propose that -Oz implies -mthumb.



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