[LLVMdev] Register allocation of stack slots

[Christian Sayer]

Dan,

thanks for your hints about the post-RA scheduler.

However, I have difficulties creating a reasonably small and concise
testcase for the problem I described, and it's on my own target anyway.
In principle, I see the following:

%theStruct = type { %theStruct2, %theStruct3, i16, ... }

define void @f1(%theStruct* %tmp) {

// initialize some locals
%a= alloca i16, align 2
store i16 1, i16* %a      ;similar b ...
.
.

// GEP some pointers to elements of tmp
%x = getelementptr %theStruct* %tmp, i64 0, i32 13    ; similiar y,z...
.
.

call void f2 (%theStruct2* %x, %theStruct2* %y, %theStruct3* %z, i16* %a, i16* %b, ...)

%var = getelementptr %theStruct* %tmp, i64 0, i32 7
store i16 0, i16* %var

ret void

}

Without the penultimate instruction (store something into the struct),
registers for locals init like a, b, are allocated as I expect, i.e. one for
each constant (the architecture needs to do a mov and a store to initialize memory).
With these two instructions, the initialization of all the locals are done using only
one register, which results in reloads of locals just initialized before.

Well I don't know if it is possible to say anything about that, but maybe someone
has a clue?

thank you,

Christian






 --
  Christian SAYER



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