llvm dev - Oct 2011 - [LLVMdev] Fixing segmented stacks

> it should be expanded late: In lib/Target/X86/X86MCInstLower.cpp.
This is exactly what I was missing.  Thanks a ton! :)
-- 
Sanjoy Das
http://playingwithpointers.com

On Oct 18, 2011, at 2:33 PM, Sanjoy Das wrote:
>> it should be expanded late: In lib/Target/X86/X86MCInstLower.cpp.
> 
> This is exactly what I was missing.  Thanks a ton! :)
We have three pseudo expansion passes:

1. ExpandISelPseudos.cpp - For instructions that may need to create basic
blocks, like CMOV and atomics.

2. ExpandPostRAPseudos.cpp - For instructions used to trick the register
allocator into doing the right thing, and COPY instructions created by live
range splitting.

3. *MCInstLower.cpp - For instructions that need to trick all of codegen.

Pseudos should be expanded as early as possible.  Many of the instructions
currently expanded in X86MCInstLower could be moved to the PostRA expansion
pass.  That would also allow them to be converted into pure isPseudo=1
instructions instead of just isCodeGenOnly=1.

/jakob

On Oct 18, 2011, at 2:46 PM, Jakob Stoklund Olesen wrote:
> 
> On Oct 18, 2011, at 2:33 PM, Sanjoy Das wrote:
> 
>>> it should be expanded late: In lib/Target/X86/X86MCInstLower.cpp.
>> 
>> This is exactly what I was missing.  Thanks a ton! :)
> 
> We have three pseudo expansion passes:
> 
> 1. ExpandISelPseudos.cpp - For instructions that may need to create basic
blocks, like CMOV and atomics.
> 
> 2. ExpandPostRAPseudos.cpp - For instructions used to trick the register
allocator into doing the right thing, and COPY instructions created by live
range splitting.
> 
> 3. *MCInstLower.cpp - For instructions that need to trick all of codegen.
> 
> Pseudos should be expanded as early as possible.  Many of the instructions
currently expanded in X86MCInstLower could be moved to the PostRA expansion
pass.  That would also allow them to be converted into pure isPseudo=1
instructions instead of just isCodeGenOnly=1.
FWIW, even those expanded at MCLowering time can be pure pseudos. There is no
need to use isCodeGenOnly definitions for any new code. Those that exist are
pure legacy.

-Jim