+++ /dev/null
-//===-- NVPTXFavorNonGenericAddrSpace.cpp - ---------------------*- C++ -*-===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// FIXME: This pass is deprecated in favor of NVPTXInferAddressSpaces, which
-// uses a new algorithm that handles pointer induction variables.
-//
-// When a load/store accesses the generic address space, checks whether the
-// address is casted from a non-generic address space. If so, remove this
-// addrspacecast because accessing non-generic address spaces is typically
-// faster. Besides removing addrspacecasts directly used by loads/stores, this
-// optimization also recursively traces into a GEP's pointer operand and a
-// bitcast's source to find more eliminable addrspacecasts.
-//
-// For instance, the code below loads a float from an array allocated in
-// addrspace(3).
-//
-// %0 = addrspacecast [10 x float] addrspace(3)* @a to [10 x float]*
-// %1 = gep [10 x float]* %0, i64 0, i64 %i
-// %2 = bitcast float* %1 to i32*
-// %3 = load i32* %2 ; emits ld.u32
-//
-// First, function hoistAddrSpaceCastFrom reorders the addrspacecast, the GEP,
-// and the bitcast to expose more optimization opportunities to function
-// optimizeMemoryInst. The intermediate code looks like:
-//
-// %0 = gep [10 x float] addrspace(3)* @a, i64 0, i64 %i
-// %1 = bitcast float addrspace(3)* %0 to i32 addrspace(3)*
-// %2 = addrspacecast i32 addrspace(3)* %1 to i32*
-// %3 = load i32* %2 ; still emits ld.u32, but will be optimized shortly
-//
-// Then, function optimizeMemoryInstruction detects a load from addrspacecast'ed
-// generic pointers, and folds the load and the addrspacecast into a load from
-// the original address space. The final code looks like:
-//
-// %0 = gep [10 x float] addrspace(3)* @a, i64 0, i64 %i
-// %1 = bitcast float addrspace(3)* %0 to i32 addrspace(3)*
-// %3 = load i32 addrspace(3)* %1 ; emits ld.shared.f32
-//
-// This pass may remove an addrspacecast in a different BB. Therefore, we
-// implement it as a FunctionPass.
-//
-// TODO:
-// The current implementation doesn't handle PHINodes. Eliminating
-// addrspacecasts used by PHINodes is trickier because PHINodes can introduce
-// loops in data flow. For example,
-//
-// %generic.input = addrspacecast float addrspace(3)* %input to float*
-// loop:
-// %y = phi [ %generic.input, %y2 ]
-// %y2 = getelementptr %y, 1
-// %v = load %y2
-// br ..., label %loop, ...
-//
-// Marking %y2 shared depends on marking %y shared, but %y also data-flow
-// depends on %y2. We probably need an iterative fix-point algorithm on handle
-// this case.
-//
-//===----------------------------------------------------------------------===//
-
-#include "NVPTX.h"
-#include "llvm/IR/Function.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/Operator.h"
-#include "llvm/Support/CommandLine.h"
-
-using namespace llvm;
-
-// An option to disable this optimization. Enable it by default.
-static cl::opt<bool> DisableFavorNonGeneric(
- "disable-nvptx-favor-non-generic",
- cl::init(false),
- cl::desc("Do not convert generic address space usage "
- "to non-generic address space usage"),
- cl::Hidden);
-
-namespace {
-/// \brief NVPTXFavorNonGenericAddrSpaces
-class NVPTXFavorNonGenericAddrSpaces : public FunctionPass {
-public:
- static char ID;
- NVPTXFavorNonGenericAddrSpaces() : FunctionPass(ID) {}
- bool runOnFunction(Function &F) override;
-
-private:
- /// Optimizes load/store instructions. Idx is the index of the pointer operand
- /// (0 for load, and 1 for store). Returns true if it changes anything.
- bool optimizeMemoryInstruction(Instruction *I, unsigned Idx);
- /// Recursively traces into a GEP's pointer operand or a bitcast's source to
- /// find an eliminable addrspacecast, and hoists that addrspacecast to the
- /// outermost level. For example, this function transforms
- /// bitcast(gep(gep(addrspacecast(X))))
- /// to
- /// addrspacecast(bitcast(gep(gep(X)))).
- ///
- /// This reordering exposes to optimizeMemoryInstruction more
- /// optimization opportunities on loads and stores.
- ///
- /// If this function successfully hoists an eliminable addrspacecast or V is
- /// already such an addrspacecast, it returns the transformed value (which is
- /// guaranteed to be an addrspacecast); otherwise, it returns nullptr.
- Value *hoistAddrSpaceCastFrom(Value *V, int Depth = 0);
- /// Helper function for GEPs.
- Value *hoistAddrSpaceCastFromGEP(GEPOperator *GEP, int Depth);
- /// Helper function for bitcasts.
- Value *hoistAddrSpaceCastFromBitCast(BitCastOperator *BC, int Depth);
-};
-}
-
-char NVPTXFavorNonGenericAddrSpaces::ID = 0;
-
-namespace llvm {
-void initializeNVPTXFavorNonGenericAddrSpacesPass(PassRegistry &);
-}
-INITIALIZE_PASS(NVPTXFavorNonGenericAddrSpaces, "nvptx-favor-non-generic",
- "Remove unnecessary non-generic-to-generic addrspacecasts",
- false, false)
-
-// Decides whether V is an addrspacecast and shortcutting V in load/store is
-// valid and beneficial.
-static bool isEliminableAddrSpaceCast(Value *V) {
- // Returns false if V is not even an addrspacecast.
- Operator *Cast = dyn_cast<Operator>(V);
- if (Cast == nullptr || Cast->getOpcode() != Instruction::AddrSpaceCast)
- return false;
-
- Value *Src = Cast->getOperand(0);
- PointerType *SrcTy = cast<PointerType>(Src->getType());
- PointerType *DestTy = cast<PointerType>(Cast->getType());
- // TODO: For now, we only handle the case where the addrspacecast only changes
- // the address space but not the type. If the type also changes, we could
- // still get rid of the addrspacecast by adding an extra bitcast, but we
- // rarely see such scenarios.
- if (SrcTy->getElementType() != DestTy->getElementType())
- return false;
-
- // Checks whether the addrspacecast is from a non-generic address space to the
- // generic address space.
- return (SrcTy->getAddressSpace() != AddressSpace::ADDRESS_SPACE_GENERIC &&
- DestTy->getAddressSpace() == AddressSpace::ADDRESS_SPACE_GENERIC);
-}
-
-Value *NVPTXFavorNonGenericAddrSpaces::hoistAddrSpaceCastFromGEP(
- GEPOperator *GEP, int Depth) {
- Value *NewOperand =
- hoistAddrSpaceCastFrom(GEP->getPointerOperand(), Depth + 1);
- if (NewOperand == nullptr)
- return nullptr;
-
- // hoistAddrSpaceCastFrom returns an eliminable addrspacecast or nullptr.
- assert(isEliminableAddrSpaceCast(NewOperand));
- Operator *Cast = cast<Operator>(NewOperand);
-
- SmallVector<Value *, 8> Indices(GEP->idx_begin(), GEP->idx_end());
- Value *NewASC;
- if (Instruction *GEPI = dyn_cast<Instruction>(GEP)) {
- // GEP = gep (addrspacecast X), indices
- // =>
- // NewGEP = gep X, indices
- // NewASC = addrspacecast NewGEP
- GetElementPtrInst *NewGEP = GetElementPtrInst::Create(
- GEP->getSourceElementType(), Cast->getOperand(0), Indices,
- "", GEPI);
- NewGEP->setIsInBounds(GEP->isInBounds());
- NewGEP->takeName(GEP);
- NewASC = new AddrSpaceCastInst(NewGEP, GEP->getType(), "", GEPI);
- // Without RAUWing GEP, the compiler would visit GEP again and emit
- // redundant instructions. This is exercised in test @rauw in
- // access-non-generic.ll.
- GEP->replaceAllUsesWith(NewASC);
- } else {
- // GEP is a constant expression.
- Constant *NewGEP = ConstantExpr::getGetElementPtr(
- GEP->getSourceElementType(), cast<Constant>(Cast->getOperand(0)),
- Indices, GEP->isInBounds());
- NewASC = ConstantExpr::getAddrSpaceCast(NewGEP, GEP->getType());
- }
- return NewASC;
-}
-
-Value *NVPTXFavorNonGenericAddrSpaces::hoistAddrSpaceCastFromBitCast(
- BitCastOperator *BC, int Depth) {
- Value *NewOperand = hoistAddrSpaceCastFrom(BC->getOperand(0), Depth + 1);
- if (NewOperand == nullptr)
- return nullptr;
-
- // hoistAddrSpaceCastFrom returns an eliminable addrspacecast or nullptr.
- assert(isEliminableAddrSpaceCast(NewOperand));
- Operator *Cast = cast<Operator>(NewOperand);
-
- // Cast = addrspacecast Src
- // BC = bitcast Cast
- // =>
- // Cast' = bitcast Src
- // BC' = addrspacecast Cast'
- Value *Src = Cast->getOperand(0);
- Type *TypeOfNewCast =
- PointerType::get(BC->getType()->getPointerElementType(),
- Src->getType()->getPointerAddressSpace());
- Value *NewBC;
- if (BitCastInst *BCI = dyn_cast<BitCastInst>(BC)) {
- Value *NewCast = new BitCastInst(Src, TypeOfNewCast, "", BCI);
- NewBC = new AddrSpaceCastInst(NewCast, BC->getType(), "", BCI);
- NewBC->takeName(BC);
- // Without RAUWing BC, the compiler would visit BC again and emit
- // redundant instructions. This is exercised in test @rauw in
- // access-non-generic.ll.
- BC->replaceAllUsesWith(NewBC);
- } else {
- // BC is a constant expression.
- Constant *NewCast =
- ConstantExpr::getBitCast(cast<Constant>(Src), TypeOfNewCast);
- NewBC = ConstantExpr::getAddrSpaceCast(NewCast, BC->getType());
- }
- return NewBC;
-}
-
-Value *NVPTXFavorNonGenericAddrSpaces::hoistAddrSpaceCastFrom(Value *V,
- int Depth) {
- // Returns V if V is already an eliminable addrspacecast.
- if (isEliminableAddrSpaceCast(V))
- return V;
-
- // Limit the depth to prevent this recursive function from running too long.
- const int MaxDepth = 20;
- if (Depth >= MaxDepth)
- return nullptr;
-
- // If V is a GEP or bitcast, hoist the addrspacecast if any from its pointer
- // operand. This enables optimizeMemoryInstruction to shortcut addrspacecasts
- // that are not directly used by the load/store.
- if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
- return hoistAddrSpaceCastFromGEP(GEP, Depth);
-
- if (BitCastOperator *BC = dyn_cast<BitCastOperator>(V))
- return hoistAddrSpaceCastFromBitCast(BC, Depth);
-
- return nullptr;
-}
-
-bool NVPTXFavorNonGenericAddrSpaces::optimizeMemoryInstruction(Instruction *MI,
- unsigned Idx) {
- Value *NewOperand = hoistAddrSpaceCastFrom(MI->getOperand(Idx));
- if (NewOperand == nullptr)
- return false;
-
- // load/store (addrspacecast X) => load/store X if shortcutting the
- // addrspacecast is valid and can improve performance.
- //
- // e.g.,
- // %1 = addrspacecast float addrspace(3)* %0 to float*
- // %2 = load float* %1
- // ->
- // %2 = load float addrspace(3)* %0
- //
- // Note: the addrspacecast can also be a constant expression.
- assert(isEliminableAddrSpaceCast(NewOperand));
- Operator *ASC = dyn_cast<Operator>(NewOperand);
- MI->setOperand(Idx, ASC->getOperand(0));
- return true;
-}
-
-bool NVPTXFavorNonGenericAddrSpaces::runOnFunction(Function &F) {
- if (DisableFavorNonGeneric || skipFunction(F))
- return false;
-
- bool Changed = false;
- for (BasicBlock &B : F) {
- for (Instruction &I : B) {
- if (isa<LoadInst>(I)) {
- // V = load P
- Changed |= optimizeMemoryInstruction(&I, 0);
- } else if (isa<StoreInst>(I)) {
- // store V, P
- Changed |= optimizeMemoryInstruction(&I, 1);
- }
- }
- }
- return Changed;
-}
-
-FunctionPass *llvm::createNVPTXFavorNonGenericAddrSpacesPass() {
- return new NVPTXFavorNonGenericAddrSpaces();
-}
; RUN: llc < %s -march=nvptx -mcpu=sm_20 | FileCheck %s --check-prefix PTX
; RUN: llc < %s -march=nvptx64 -mcpu=sm_20 | FileCheck %s --check-prefix PTX
-; RUN: llc < %s -march=nvptx64 -mcpu=sm_20 -nvptx-use-infer-addrspace=true | FileCheck %s --check-prefix PTX
-; RUN: llc < %s -march=nvptx64 -mcpu=sm_20 -nvptx-use-infer-addrspace=false | FileCheck %s --check-prefix PTX
-; RUN: opt < %s -S -nvptx-favor-non-generic -dce | FileCheck %s --check-prefix IR
-; RUN: opt < %s -S -nvptx-infer-addrspace | FileCheck %s --check-prefix IR --check-prefix IR-WITH-LOOP
+; RUN: opt < %s -S -nvptx-infer-addrspace | FileCheck %s --check-prefix IR
@array = internal addrspace(3) global [10 x float] zeroinitializer, align 4
@scalar = internal addrspace(3) global float 0.000000e+00, align 4
}
define void @loop() {
-; IR-WITH-LOOP-LABEL: @loop(
+; IR-LABEL: @loop(
entry:
%p = addrspacecast [10 x float] addrspace(3)* @array to float*
%end = getelementptr float, float* %p, i64 10
loop:
%i = phi float* [ %p, %entry ], [ %i2, %loop ]
-; IR-WITH-LOOP: phi float addrspace(3)* [ %p, %entry ], [ %i2, %loop ]
+; IR: phi float addrspace(3)* [ %p, %entry ], [ %i2, %loop ]
%v = load float, float* %i
-; IR-WITH-LOOP: %v = load float, float addrspace(3)* %i
+; IR: %v = load float, float addrspace(3)* %i
call void @use(float %v)
%i2 = getelementptr float, float* %i, i64 1
-; IR-WITH-LOOP: %i2 = getelementptr float, float addrspace(3)* %i, i64 1
+; IR: %i2 = getelementptr float, float addrspace(3)* %i, i64 1
%exit_cond = icmp eq float* %i2, %end
br i1 %exit_cond, label %exit, label %loop
@generic_end = external global float*
define void @loop_with_generic_bound() {
-; IR-WITH-LOOP-LABEL: @loop_with_generic_bound(
+; IR-LABEL: @loop_with_generic_bound(
entry:
%p = addrspacecast [10 x float] addrspace(3)* @array to float*
%end = load float*, float** @generic_end
loop:
%i = phi float* [ %p, %entry ], [ %i2, %loop ]
-; IR-WITH-LOOP: phi float addrspace(3)* [ %p, %entry ], [ %i2, %loop ]
+; IR: phi float addrspace(3)* [ %p, %entry ], [ %i2, %loop ]
%v = load float, float* %i
-; IR-WITH-LOOP: %v = load float, float addrspace(3)* %i
+; IR: %v = load float, float addrspace(3)* %i
call void @use(float %v)
%i2 = getelementptr float, float* %i, i64 1
-; IR-WITH-LOOP: %i2 = getelementptr float, float addrspace(3)* %i, i64 1
+; IR: %i2 = getelementptr float, float addrspace(3)* %i, i64 1
%exit_cond = icmp eq float* %i2, %end
-; IR-WITH-LOOP: addrspacecast float addrspace(3)* %i2 to float*
-; IR-WITH-LOOP: icmp eq float* %{{[0-9]+}}, %end
+; IR: addrspacecast float addrspace(3)* %i2 to float*
+; IR: icmp eq float* %{{[0-9]+}}, %end
br i1 %exit_cond, label %exit, label %loop
exit: