AMDGPU: Add pass to replace out arguments

It is better to return arguments directly in registers
if we are making a call rather than introducing expensive
stack usage. In one of sample compile from one of
Blender's many kernel variants, this fires on about
~20 different functions. Future improvements may be to
recognize simple cases where the pointer is indexing a small
array. This also fails when the store to the out argument
is in a separate block from the return, which happens in
a few of the Blender functions. This should also probably
be using MemorySSA which might help with that.

I'm not sure this is correct as a FunctionPass, but
MemoryDependenceAnalysis seems to not work with
a ModulePass.

I'm also not sure where it should run.I think it should
run  before DeadArgumentElimination, so maybe either
EP_CGSCCOptimizerLate or EP_ScalarOptimizerLate.

llvm-svn: 309416

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPU.h b/llvm/lib/Target/AMDGPU/AMDGPU.h
index bbb542eb4fc..f4df15e9500 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPU.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPU.h
@@ -51,6 +51,7 @@ FunctionPass *createSIInsertWaitsPass();
 FunctionPass *createSIInsertWaitcntsPass();
 FunctionPass *createAMDGPUCodeGenPreparePass();
 FunctionPass *createAMDGPUMachineCFGStructurizerPass();
+FunctionPass *createAMDGPURewriteOutArgumentsPass();
 
 void initializeAMDGPUMachineCFGStructurizerPass(PassRegistry&);
 extern char &AMDGPUMachineCFGStructurizerID;
@@ -65,6 +66,9 @@ ModulePass *createAMDGPULowerIntrinsicsPass();
 void initializeAMDGPULowerIntrinsicsPass(PassRegistry &);
 extern char &AMDGPULowerIntrinsicsID;
 
+void initializeAMDGPURewriteOutArgumentsPass(PassRegistry &);
+extern char &AMDGPURewriteOutArgumentsID;
+
 void initializeSIFoldOperandsPass(PassRegistry &);
 extern char &SIFoldOperandsID;