[PATCH] D30163: [ELF] - Postpone evaluation of LMA offset.

[George Rimar via llvm-commits]

>This is a bit confusing. Why do we need to hold information in
>LinkerScript.h? OutputSectionCommand *Cmd holds the expression, can't we
>just evaluate it once the virtual addresses are computed?

I think we can't. Testcase at.s shows why: 
.aaa : AT(0x2000)  {  *(.aaa)  } 
.bbb : {  *(.bbb) } 

In that case we should do:
  // If neither AT nor AT> is specified for an allocatable section, the linker
  // will set the LMA such that the difference between VMA and LMA for the
  // section is the same as the preceding output section in the same region
  // https://sourceware.org/binutils/docs-2.20/ld/Output-Section-LMA.html

We calculate LMA as:
uint64_t getLMA() const { return Addr + LMAOffset; }

So VA(.bbb) - VA(.aaa) == LMA(.bbb) - LMA(.aaa).

And at the moment of computing VA for .bbb its command
does not have LMA expression. (We only have it for .aaa).

We also create phdrs later, so do not know FirstInPtLoad at this moment,
so I think we can't find first output section in the current load to take
its LMA offset at this step too.

George.