ModulePass using BreakCriticalEdges

Project Infrastructure LLVM Dev List Archives
1

Hi,

I'm writing a ModulePass that needs critical edges split up. I have the
statement

  AU.addRequiredID(BreakCriticalEdgesID);

in my getAnalysisUsage() but the pass never gets executed.

I guess I have to request pass execution for each function, but I can't
get behind how to do that, since there is no analysis group for that
kind of transformation.

Thanks, Andi

2

Hi all,

i'm working atm on a backend for a processor architecture that is
capable of storing the carry flag of ADDC in an 1-bit register class. So
I tried to lower the ADDC instruction to generate two register values as
result. On the tablegen description of the instruction i came across the
tablegen restriction that only one output result of one instruction is
possible:

  assert(NumResults <= 1 &&
         "We only work with nodes with zero or one result so far!");

So my question is now how much work it would be to remove this
restriction in tablegen. What do I have to take into consideration?

Thanks,
Timo Stripf

3

Hi,

Andreas Neustifter wrote:

I'm writing a ModulePass that needs critical edges split up. I have the
statement

  AU.addRequiredID(BreakCriticalEdgesID);

in my getAnalysisUsage() but the pass never gets executed.

I guess I have to request pass execution for each function, but I can't
get behind how to do that, since there is no analysis group for that
kind of transformation.

I now also added a (selfwritten) FunctionPass with is member of the
analysis group ProfileInfo

  AU.addRequiredID(ProfileEstimatorID);
  AU.addRequired<ProfileInfo>();

and fetching the ProfileInfo by executing

  ProfileInfo *PI = &getAnalysis<ProfileInfo>(*F);

and now the BreakCriticalEdge pass gets also executed.

Seems to me that the FunctionPassManager generated when requesting the
ProfileInfo also executes the BreakCriticalEdges pass.

Andi

4

This isn't an answer to your question, but you can also use the SplitCriticalEdge family of functions from your pass, without using the BreakCriticalEdges pass.

-Chris