[NVPTX] Added NVVMIntrRange pass

NVVMIntrRange adds !range metadata to calls of NVVM intrinsics
that return values within known limited range.

This allows LLVM to generate optimal code for indexing arrays
based on tid/ctaid which is a frequently used pattern in CUDA code.

Differential Revision: http://reviews.llvm.org/D20644

llvm-svn: 270872

1 files changed, 154 insertions, 0 deletions

diff --git a/llvm/lib/Target/NVPTX/NVVMIntrRange.cpp b/llvm/lib/Target/NVPTX/NVVMIntrRange.cpp
new file mode 100644
index 00000000000..09f328d4c53
--- /dev/null
+++ b/llvm/lib/Target/NVPTX/NVVMIntrRange.cpp
@@ -0,0 +1,154 @@
+//===- NVVMIntrRange.cpp - Set !range metadata for NVVM intrinsics --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass adds appropriate !range metadata for calls to NVVM
+// intrinsics that return a limited range of values.
+//
+//===----------------------------------------------------------------------===//
+
+#include "NVPTX.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/InstIterator.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Instructions.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "nvvm-intr-range"
+
+namespace llvm { void initializeNVVMIntrRangePass(PassRegistry &); }
+
+// Add !range metadata based on limits of given SM variant.
+static cl::opt<unsigned> NVVMIntrRangeSM("nvvm-intr-range-sm", cl::init(20),
+                                         cl::Hidden, cl::desc("SM variant"));
+
+namespace {
+class NVVMIntrRange : public FunctionPass {
+ private:
+   struct {
+     unsigned x, y, z;
+   } MaxBlockSize, MaxGridSize;
+
+ public:
+   static char ID;
+   NVVMIntrRange() : NVVMIntrRange(NVVMIntrRangeSM) {}
+   NVVMIntrRange(unsigned int SmVersion)
+       : FunctionPass(ID), MaxBlockSize{1024, 1024, 64},
+         MaxGridSize{SmVersion >= 30 ? 0x7fffffffu : 0xffffu, 0xffff, 0xffff} {
+     initializeNVVMIntrRangePass(*PassRegistry::getPassRegistry());
+   }
+
+   bool runOnFunction(Function &) override;
+};
+}
+
+FunctionPass *llvm::createNVVMIntrRangePass(unsigned int SmVersion) {
+  return new NVVMIntrRange(SmVersion);
+}
+
+char NVVMIntrRange::ID = 0;
+INITIALIZE_PASS(NVVMIntrRange, "nvvm-intr-range",
+                "Add !range metadata to NVVM intrinsics.", false, false)
+
+// Adds the passed-in [Low,High) range information as metadata to the
+// passed-in call instruction.
+static bool addRangeMetadata(uint64_t Low, uint64_t High, CallInst *C) {
+  LLVMContext &Context = C->getParent()->getContext();
+  IntegerType *Int32Ty = Type::getInt32Ty(Context);
+  Metadata *LowAndHigh[] = {
+      ConstantAsMetadata::get(ConstantInt::get(Int32Ty, Low)),
+      ConstantAsMetadata::get(ConstantInt::get(Int32Ty, High))};
+  C->setMetadata(LLVMContext::MD_range, MDNode::get(Context, LowAndHigh));
+  return true;
+}
+
+bool NVVMIntrRange::runOnFunction(Function &F) {
+  // Go through the calls in this function.
+  bool Changed = false;
+  for (Instruction &I : instructions(F)) {
+    CallInst *Call = dyn_cast<CallInst>(&I);
+    if (!Call)
+      continue;
+
+    if (Function *Callee = Call->getCalledFunction()) {
+      switch (Callee->getIntrinsicID()) {
+      // Index within block
+      case Intrinsic::ptx_read_tid_x:
+      case Intrinsic::nvvm_read_ptx_sreg_tid_x:
+        Changed |= addRangeMetadata(0, MaxBlockSize.x, Call);
+        break;
+      case Intrinsic::ptx_read_tid_y:
+      case Intrinsic::nvvm_read_ptx_sreg_tid_y:
+        Changed |= addRangeMetadata(0, MaxBlockSize.y, Call);
+        break;
+      case Intrinsic::ptx_read_tid_z:
+      case Intrinsic::nvvm_read_ptx_sreg_tid_z:
+        Changed |= addRangeMetadata(0, MaxBlockSize.z, Call);
+        break;
+
+      // Block size
+      case Intrinsic::ptx_read_ntid_x:
+      case Intrinsic::nvvm_read_ptx_sreg_ntid_x:
+        Changed |= addRangeMetadata(1, MaxBlockSize.x+1, Call);
+        break;
+      case Intrinsic::ptx_read_ntid_y:
+      case Intrinsic::nvvm_read_ptx_sreg_ntid_y:
+        Changed |= addRangeMetadata(1, MaxBlockSize.y+1, Call);
+        break;
+      case Intrinsic::ptx_read_ntid_z:
+      case Intrinsic::nvvm_read_ptx_sreg_ntid_z:
+        Changed |= addRangeMetadata(1, MaxBlockSize.z+1, Call);
+        break;
+
+      // Index within grid
+      case Intrinsic::ptx_read_ctaid_x:
+      case Intrinsic::nvvm_read_ptx_sreg_ctaid_x:
+        Changed |= addRangeMetadata(0, MaxGridSize.x, Call);
+        break;
+      case Intrinsic::ptx_read_ctaid_y:
+      case Intrinsic::nvvm_read_ptx_sreg_ctaid_y:
+        Changed |= addRangeMetadata(0, MaxGridSize.y, Call);
+        break;
+      case Intrinsic::ptx_read_ctaid_z:
+      case Intrinsic::nvvm_read_ptx_sreg_ctaid_z:
+        Changed |= addRangeMetadata(0, MaxGridSize.z, Call);
+        break;
+
+      // Grid size
+      case Intrinsic::ptx_read_nctaid_x:
+      case Intrinsic::nvvm_read_ptx_sreg_nctaid_x:
+        Changed |= addRangeMetadata(1, MaxGridSize.x+1, Call);
+        break;
+      case Intrinsic::ptx_read_nctaid_y:
+      case Intrinsic::nvvm_read_ptx_sreg_nctaid_y:
+        Changed |= addRangeMetadata(1, MaxGridSize.y+1, Call);
+        break;
+      case Intrinsic::ptx_read_nctaid_z:
+      case Intrinsic::nvvm_read_ptx_sreg_nctaid_z:
+        Changed |= addRangeMetadata(1, MaxGridSize.z+1, Call);
+        break;
+
+      // warp size is constant 32.
+      case Intrinsic::nvvm_read_ptx_sreg_warpsize:
+        Changed |= addRangeMetadata(32, 32+1, Call);
+        break;
+
+      // Lane ID is [0..warpsize)
+      case Intrinsic::ptx_read_laneid:
+        Changed |= addRangeMetadata(0, 32, Call);
+        break;
+
+      default:
+        break;
+      }
+    }
+  }
+
+  return Changed;
+}