[llvm] r267765 - [NVPTX] Run NVVMReflect at the beginning of IR passes.

[Justin Lebar via llvm-commits]

Author: jlebar
Date: Wed Apr 27 14:13:37 2016
New Revision: 267765

URL: http://llvm.org/viewvc/llvm-project?rev=267765&view=rev
Log:
[NVPTX] Run NVVMReflect at the beginning of IR passes.

Summary:
Currently the NVVMReflect pass is run at the beginning of our backend
passes.  But really, it should be run as early as possible, as it's
simply resolving an "if" statement in code.  So copy it into
TargetMachine::addEarlyAsPossiblePasses.

We still run it at the beginning of the backend passes, since it's
needed for correctness when lowering to nvptx.

(Specifically, NVVMReflect changes each call to the __nvvm_reflect
function or llvm.nvvm.reflect intrinsic into an integer constant, based
on the pass's configuration.  Clearly we miss many optimization
opportunities if we perform this transformation at the beginning of
codegen.)

Reviewers: rnk

Subscribers: tra, llvm-commits, jholewinski

Differential Revision: http://reviews.llvm.org/D18616

Modified:
    llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.cpp
    llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.h

Modified: llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.cpp?rev=267765&r1=267764&r2=267765&view=diff
==============================================================================
--- llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.cpp Wed Apr 27 14:13:37 2016
@@ -167,6 +167,10 @@ TargetPassConfig *NVPTXTargetMachine::cr
   return new NVPTXPassConfig(this, PM);
 }
 
+void NVPTXTargetMachine::addEarlyAsPossiblePasses(PassManagerBase &PM) {
+  PM.add(createNVVMReflectPass());
+}
+
 TargetIRAnalysis NVPTXTargetMachine::getTargetIRAnalysis() {
   return TargetIRAnalysis([this](const Function &F) {
     return TargetTransformInfo(NVPTXTTIImpl(this, F));
@@ -228,7 +232,12 @@ void NVPTXPassConfig::addIRPasses() {
   disablePass(&FuncletLayoutID);
   disablePass(&PatchableFunctionID);
 
+  // NVVMReflectPass is added in addEarlyAsPossiblePasses, so hopefully running
+  // it here does nothing.  But since we need it for correctness when lowering
+  // to NVPTX, run it here too, in case whoever built our pass pipeline didn't
+  // call addEarlyAsPossiblePasses.
   addPass(createNVVMReflectPass());
+
   if (getOptLevel() != CodeGenOpt::None)
     addPass(createNVPTXImageOptimizerPass());
   addPass(createNVPTXAssignValidGlobalNamesPass());

Modified: llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.h?rev=267765&r1=267764&r2=267765&view=diff
==============================================================================
--- llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.h (original)
+++ llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.h Wed Apr 27 14:13:37 2016
@@ -61,6 +61,7 @@ public:
     return TLOF.get();
   }
 
+  void addEarlyAsPossiblePasses(PassManagerBase &PM) override;
   TargetIRAnalysis getTargetIRAnalysis() override;
 
 }; // NVPTXTargetMachine.