1 //===-- AMDGPUTargetTransformInfo.cpp - AMDGPU specific TTI pass ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 // This file implements a TargetTransformInfo analysis pass specific to the
12 // AMDGPU target machine. It uses the target's detailed information to provide
13 // more precise answers to certain TTI queries, while letting the target
14 // independent and default TTI implementations handle the rest.
16 //===----------------------------------------------------------------------===//
18 #include "AMDGPUTargetTransformInfo.h"
19 #include "llvm/Analysis/LoopInfo.h"
20 #include "llvm/Analysis/TargetTransformInfo.h"
21 #include "llvm/Analysis/ValueTracking.h"
22 #include "llvm/CodeGen/BasicTTIImpl.h"
23 #include "llvm/Support/Debug.h"
24 #include "llvm/Target/CostTable.h"
25 #include "llvm/Target/TargetLowering.h"
28 #define DEBUG_TYPE "AMDGPUtti"
30 void AMDGPUTTIImpl::getUnrollingPreferences(Loop *L,
31 TTI::UnrollingPreferences &UP) {
32 UP.Threshold = 300; // Twice the default.
36 // TODO: Do we want runtime unrolling?
38 for (const BasicBlock *BB : L->getBlocks()) {
39 for (const Instruction &I : *BB) {
40 const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&I);
41 if (!GEP || GEP->getAddressSpace() != AMDGPUAS::PRIVATE_ADDRESS)
44 const Value *Ptr = GEP->getPointerOperand();
45 const AllocaInst *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Ptr));
47 // We want to do whatever we can to limit the number of alloca
48 // instructions that make it through to the code generator. allocas
49 // require us to use indirect addressing, which is slow and prone to
50 // compiler bugs. If this loop does an address calculation on an
51 // alloca ptr, then we want to use a higher than normal loop unroll
52 // threshold. This will give SROA a better chance to eliminate these
55 // Don't use the maximum allowed value here as it will make some
56 // programs way too big.
63 unsigned AMDGPUTTIImpl::getNumberOfRegisters(bool Vec) {
67 // Number of VGPRs on SI.
68 if (ST->getGeneration() >= AMDGPUSubtarget::SOUTHERN_ISLANDS)
71 return 4 * 128; // XXX - 4 channels. Should these count as vector instead?
74 unsigned AMDGPUTTIImpl::getRegisterBitWidth(bool) { return 32; }
76 unsigned AMDGPUTTIImpl::getMaxInterleaveFactor() {
77 // Semi-arbitrary large amount.