[PATCH] D31852: [PowerPC] Convert reg/reg instructions fed by constants to reg/imm instructions (pre and post RA)

[Hal Finkel via Phabricator via llvm-commits]

hfinkel accepted this revision.
hfinkel added a comment.
This revision is now accepted and ready to land.

In https://reviews.llvm.org/D31852#937664, @nemanjai wrote:

> @hfinkel What do you think about this? Do we want to proceed with this? We actually convert a lot of instructions with this and it has a proven effect on performance. The updated patch actually converts and deletes an extra ~1,000 instructions in bootstrap.


Yes, we should proceed.



================
Comment at: lib/Target/PowerPC/PPCInstrInfo.cpp:2314
+  unsigned ConstantOperand = ~0U;
+  MachineInstr *DefMI = getConstantDefMI(MI, ConstantOperand,
+                                         SeenIntermediateUse);
----------------
I see why you did this, but I don't like the interface to this function: it is unintuitive that it might return non-null, and yet, you also need to check that the ConstantOp is not -1 to know if the return value is valid. Can you please change this so that it uniformly returns non-null only if it succeeds (and, thus, the constant is valid).


Repository:
  rL LLVM

https://reviews.llvm.org/D31852