[LLVMdev] [PATCH] Fix arm sbfx/ubfx generation

[David Conrad]

On Oct 20, 2009, at 10:27 PM, David Conrad wrote:

> Hi,
>
> Currently llvm can generate an invalid sbfx/ubfx op, for instance  
> when compiling encoder/analyse.c in x264 (I'll reduce this to a test  
> case if needed):

Well I just read the dev policy and saw that this was required, so  
test case attached. It'll break if llvm starts emitting the lsl r0,  
r0, #3 / asr r0, r0, #1 variants for shifts, not sure how to handle  
that.

> LSB isn't checked to ensure it's non-negative. In addition, LSB +  
> Width cannot be >32, since it reduces to (Srl_imm - Shl_imm) + (32 -  
> Srl_imm) == 32 - Shl_imm, and it was already assert()ed that 0 <  
> Shl_imm < 32. So that check is just replaced by if (LSB < 0)


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