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authorVineet Gupta <Vineet.Gupta1@synopsys.com>2016-08-16 15:04:27 -0700
committerWaldemar Brodkorb <wbx@uclibc-ng.org>2016-08-17 21:29:57 +0200
commit3e40f9669279f005f7154892539166f5081fbcb2 (patch)
tree46d8c53c35da4d60fbfc97e435810e3454b507a4 /extra
parent9725c0b6e4fda2db5c5aac0888d64dc97c69a332 (diff)
ARC: Support syscall ABI v4
The syscall ABI includes the gcc functional calling ABI since a syscall implies userland caller and kernel callee. The current gcc ABI (v3) for ARCv2 ISA required 64-bit data be passed in even-odd register pairs, (potentially punching reg holes when passing such values as args). This was partly driven by the fact that the double-word LDD/STD instructions in ARCv2 expect the register alignment and thus gcc forcing this avoids extra MOV at the cost of a few unused register (which we have plenty anyways). This however was rejected as part of upstreaming gcc port to HS. So the new ABI v4 doesn't enforce the even-odd reg restriction. Do note that for ARCompact ISA builds v3 and v4 are practically the same in terms of gcc code generation. This change is dormant for now (gcc 4.8.x based tools) and will only kick in with switch to gcc 6.x based tools. Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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