What ARM architectures does LLVM support?
I work on software written in C t开发者_高级运维hat runs on a variety of ARM processors with different architectures (ARMv5, ARMv6 mostly). We currently compile our code with a few different versions of RVDS, but we are looking at compiling some code with LLVM in order to add some custom instrumentation.
I know LLVM has ARM and Thumb targets, but what architectures does it support, specifically? Will LLVM generated code work on ARMv5? What limitations should I be aware of?
Their source code lists the following archs:
// ARM architectures.
def ArchV4T : SubtargetFeature<"v4t", "ARMArchVersion", "V4T", "ARM v4T">;
def ArchV5T : SubtargetFeature<"v5t", "ARMArchVersion", "V5T", "ARM v5T">;
def ArchV5TE : SubtargetFeature<"v5te", "ARMArchVersion", "V5TE", "ARM v5TE, v5TEj, v5TExp">;
def ArchV6 : SubtargetFeature<"v6", "ARMArchVersion", "V6", "ARM v6">;
def ArchV6M : SubtargetFeature<"v6m", "ARMArchVersion", "V6M", "ARM v6m", [FeatureNoARM, FeatureDB]>;
def ArchV6T2 : SubtargetFeature<"v6t2", "ARMArchVersion", "V6T2", "ARM v6t2", [FeatureThumb2]>;
def ArchV7A : SubtargetFeature<"v7a", "ARMArchVersion", "V7A", "ARM v7A", [FeatureThumb2, FeatureNEON, FeatureDB]>;
def ArchV7M : SubtargetFeature<"v7m", "ARMArchVersion", "V7M", "ARM v7M", [FeatureThumb2, FeatureNoARM, FeatureDB, FeatureHWDiv]>;
I have run llvm generated code on ARMv4, and ARMv6 definitely. I have some ARMv5 platforms but dont remember if I tried it there. I would assume the output of a generic -march=arm would give least common denominator (ARMv4) code, which means it will run on ARMv5. This was all embedded, no operating system type work mind you, I have not used llvm to create arm linux binaries or anything like that.
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