Add NVPTXLowerAlloca pass to convert alloca'ed memory to local address

Summary:
This is done by first adding two additional instructions to convert the
alloca returned address to local and convert it back to generic. Then
replace all uses of alloca instruction with the converted generic
address. Then we can rely NVPTXFavorNonGenericAddrSpace pass to combine
the generic addresscast and the corresponding Load, Store, Bitcast, GEP
Instruction together.

Patched by Xuetian Weng (xweng@google.com). 

Test Plan: test/CodeGen/NVPTX/lower-alloca.ll

Reviewers: jholewinski, jingyue

Reviewed By: jingyue

Subscribers: meheff, broune, eliben, jholewinski, llvm-commits

Differential Revision: http://reviews.llvm.org/D10483

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239964 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/NVPTX/CMakeLists.txt

@@ -21,6 +21,7 @@ set(NVPTXCodeGen_sources
   NVPTXInstrInfo.cpp
   NVPTXLowerAggrCopies.cpp
   NVPTXLowerKernelArgs.cpp
+  NVPTXLowerAlloca.cpp
   NVPTXMCExpr.cpp
   NVPTXPrologEpilogPass.cpp
   NVPTXRegisterInfo.cpp

lib/Target/NVPTX/NVPTX.h

@@ -70,6 +70,7 @@ MachineFunctionPass *createNVPTXPrologEpilogPass();
 MachineFunctionPass *createNVPTXReplaceImageHandlesPass();
 FunctionPass *createNVPTXImageOptimizerPass();
 FunctionPass *createNVPTXLowerKernelArgsPass(const NVPTXTargetMachine *TM);
+BasicBlockPass *createNVPTXLowerAllocaPass();
 
 bool isImageOrSamplerVal(const Value *, const Module *);
 

lib/Target/NVPTX/NVPTXLowerAlloca.cpp

@@ -0,0 +1,115 @@
+//===-- NVPTXLowerAlloca.cpp - Make alloca to use local memory =====--===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// For all alloca instructions, and add a pair of cast to local address for
+// each of them. For example,
+//
+//   %A = alloca i32
+//   store i32 0, i32* %A ; emits st.u32
+//
+// will be transformed to
+//
+//   %A = alloca i32
+//   %Local = addrspacecast i32* %A to i32 addrspace(5)*
+//   %Generic = addrspacecast i32 addrspace(5)* %A to i32*
+//   store i32 0, i32 addrspace(5)* %Generic ; emits st.local.u32
+//
+// And we will rely on NVPTXFavorNonGenericAddrSpace to combine the last
+// two instructions.
+//
+//===----------------------------------------------------------------------===//
+
+#include "NVPTX.h"
+#include "NVPTXUtilities.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Pass.h"
+
+using namespace llvm;
+
+namespace llvm {
+void initializeNVPTXLowerAllocaPass(PassRegistry &);
+}
+
+namespace {
+class NVPTXLowerAlloca : public BasicBlockPass {
+  bool runOnBasicBlock(BasicBlock &BB) override;
+
+public:
+  static char ID; // Pass identification, replacement for typeid
+  NVPTXLowerAlloca() : BasicBlockPass(ID) {}
+  const char *getPassName() const override {
+    return "convert address space of alloca'ed memory to local";
+  }
+};
+} // namespace
+
+char NVPTXLowerAlloca::ID = 1;
+
+INITIALIZE_PASS(NVPTXLowerAlloca, "nvptx-lower-alloca",
+                "Lower Alloca", false, false)
+
+// =============================================================================
+// Main function for this pass.
+// =============================================================================
+bool NVPTXLowerAlloca::runOnBasicBlock(BasicBlock &BB) {
+  bool Changed = false;
+  for (auto &I : BB) {
+    if (auto allocaInst = dyn_cast<AllocaInst>(&I)) {
+      Changed = true;
+      auto PTy = dyn_cast<PointerType>(allocaInst->getType());
+      auto ETy = PTy->getElementType();
+      auto LocalAddrTy = PointerType::get(ETy, ADDRESS_SPACE_LOCAL);
+      auto NewASCToLocal = new AddrSpaceCastInst(allocaInst, LocalAddrTy, "");
+      auto GenericAddrTy = PointerType::get(ETy, ADDRESS_SPACE_GENERIC);
+      auto NewASCToGeneric = new AddrSpaceCastInst(NewASCToLocal,
+                                                    GenericAddrTy, "");
+      NewASCToLocal->insertAfter(allocaInst);
+      NewASCToGeneric->insertAfter(NewASCToLocal);
+      for (Value::use_iterator UI = allocaInst->use_begin(),
+                                UE = allocaInst->use_end();
+            UI != UE; ) {
+        // Check Load, Store, GEP, and BitCast Uses on alloca and make them
+        // use the converted generic address, in order to expose non-generic
+        // addrspacecast to NVPTXFavorNonGenericAddrSpace. For other types
+        // of instructions this is unecessary and may introduce redudant
+        // address cast.
+        const auto &AllocaUse = *UI++;
+        auto LI = dyn_cast<LoadInst>(AllocaUse.getUser());
+        if (LI && LI->getPointerOperand() == allocaInst && !LI->isVolatile()) {
+          LI->setOperand(LI->getPointerOperandIndex(), NewASCToGeneric);
+          continue;
+        }
+        auto SI = dyn_cast<StoreInst>(AllocaUse.getUser());
+        if (SI && SI->getPointerOperand() == allocaInst && !SI->isVolatile()) {
+          SI->setOperand(SI->getPointerOperandIndex(), NewASCToGeneric);
+          continue;
+        }
+        auto GI = dyn_cast<GetElementPtrInst>(AllocaUse.getUser());
+        if (GI && GI->getPointerOperand() == allocaInst) {
+          GI->setOperand(GI->getPointerOperandIndex(), NewASCToGeneric);
+          continue;
+        }
+        auto BI = dyn_cast<BitCastInst>(AllocaUse.getUser());
+        if (BI && BI->getOperand(0) == allocaInst) {
+          BI->setOperand(0, NewASCToGeneric);
+          continue;
+        }
+      }
+    }
+  }
+  return Changed;
+}
+
+BasicBlockPass *llvm::createNVPTXLowerAllocaPass() {
+  return new NVPTXLowerAlloca();
+}

lib/Target/NVPTX/NVPTXTargetMachine.cpp

@@ -54,6 +54,7 @@ void initializeNVPTXAllocaHoistingPass(PassRegistry &);
 void initializeNVPTXAssignValidGlobalNamesPass(PassRegistry&);
 void initializeNVPTXFavorNonGenericAddrSpacesPass(PassRegistry &);
 void initializeNVPTXLowerKernelArgsPass(PassRegistry &);
+void initializeNVPTXLowerAllocaPass(PassRegistry &);
 }
 
 extern "C" void LLVMInitializeNVPTXTarget() {
@@ -70,6 +71,7 @@ extern "C" void LLVMInitializeNVPTXTarget() {
   initializeNVPTXFavorNonGenericAddrSpacesPass(
     *PassRegistry::getPassRegistry());
   initializeNVPTXLowerKernelArgsPass(*PassRegistry::getPassRegistry());
+  initializeNVPTXLowerAllocaPass(*PassRegistry::getPassRegistry());
 }
 
 static std::string computeDataLayout(bool is64Bit) {
@@ -166,12 +168,11 @@ void NVPTXPassConfig::addIRPasses() {
   addPass(createNVPTXAssignValidGlobalNamesPass());
   addPass(createGenericToNVVMPass());
   addPass(createNVPTXLowerKernelArgsPass(&getNVPTXTargetMachine()));
-  addPass(createNVPTXFavorNonGenericAddrSpacesPass());
   // NVPTXLowerKernelArgs emits alloca for byval parameters which can often
-  // be eliminated by SROA. We do not run SROA right after NVPTXLowerKernelArgs
+  // be eliminated by SROA.
-  // because we plan to merge NVPTXLowerKernelArgs and
-  // NVPTXFavorNonGenericAddrSpaces into one pass.
   addPass(createSROAPass());
+  addPass(createNVPTXLowerAllocaPass());
+  addPass(createNVPTXFavorNonGenericAddrSpacesPass());
   // FavorNonGenericAddrSpaces shortcuts unnecessary addrspacecasts, and leave
   // them unused. We could remove dead code in an ad-hoc manner, but that
   // requires manual work and might be error-prone.

test/CodeGen/NVPTX/call-with-alloca-buffer.ll

@@ -27,8 +27,9 @@ entry:
 ; CHECK: cvta.to.global.u64 %rd[[A1_REG:[0-9]+]], %rd[[A_REG]]
 ; FIXME: casting A1_REG to A2_REG is unnecessary; A2_REG is essentially A_REG
 ; CHECK: cvta.global.u64 %rd[[A2_REG:[0-9]+]], %rd[[A1_REG]]
+; CHECK: cvta.local.u64 %rd[[SP_REG:[0-9]+]]
 ; CHECK: ld.global.f32 %f[[A0_REG:[0-9]+]], [%rd[[A1_REG]]]
-; CHECK: st.f32 [%SP+0], %f[[A0_REG]]
+; CHECK: st.local.f32 [{{%rd[0-9]+}}], %f[[A0_REG]]
 
   %0 = load float, float* %a, align 4
   %1 = bitcast [16 x i8]* %buf to float*
@@ -49,7 +50,6 @@ entry:
   %7 = bitcast i8* %arrayidx7 to float*
   store float %6, float* %7, align 4
 
-; CHECK: add.u64 %rd[[SP_REG:[0-9]+]], %SP, 0
 ; CHECK:        .param .b64 param0;
 ; CHECK-NEXT:   st.param.b64  [param0+0], %rd[[A2_REG]]
 ; CHECK-NEXT:   .param .b64 param1;

test/CodeGen/NVPTX/lower-alloca.ll

@@ -0,0 +1,22 @@
+; RUN: opt < %s -S -nvptx-lower-alloca -nvptx-favor-non-generic -dce | FileCheck %s
+; RUN: llc < %s -march=nvptx64 -mcpu=sm_35 | FileCheck %s --check-prefix PTX
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64"
+target triple = "nvptx64-unknown-unknown"
+
+define void @kernel() {
+; LABEL: @lower_alloca
+; PTX-LABEL: .visible .entry kernel(
+  %A = alloca i32
+; CHECK: addrspacecast i32* %A to i32 addrspace(5)*
+; CHECK: store i32 0, i32 addrspace(5)* {{%.+}}
+; PTX: st.local.u32 [{{%rd[0-9]+}}], {{%r[0-9]+}}
+  store i32 0, i32* %A
+  call void @callee(i32* %A)
+  ret void
+}
+
+declare void @callee(i32*)
+
+!nvvm.annotations = !{!0}
+!0 = !{void ()* @kernel, !"kernel", i32 1}