[llvm-commits] [llvm] r43336 - in /llvm/trunk: lib/Transforms/Scalar/LoopStrengthReduce.cpp test/CodeGen/X86/loop-strength-reduce3.ll test/CodeGen/X86/loop-strength-reduce4.ll
Evan Cheng
evan.cheng at apple.com
Thu Oct 25 02:11:18 PDT 2007
Author: evancheng
Date: Thu Oct 25 04:11:16 2007
New Revision: 43336
URL: http://llvm.org/viewvc/llvm-project?rev=43336&view=rev
Log:
If a loop termination compare instruction is the only use of its stride,
and the compaison is against a constant value, try eliminate the stride
by moving the compare instruction to another stride and change its
constant operand accordingly. e.g.
loop:
..
v1 = v1 + 3
v2 = v2 + 1
if (v2 < 10) goto loop
=>
loop:
..
v1 = v1 + 3
if (v1 < 30) goto loop
Added:
llvm/trunk/test/CodeGen/X86/loop-strength-reduce3.ll
llvm/trunk/test/CodeGen/X86/loop-strength-reduce4.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp?rev=43336&r1=43335&r2=43336&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp Thu Oct 25 04:11:16 2007
@@ -39,9 +39,10 @@
#include <set>
using namespace llvm;
-STATISTIC(NumReduced , "Number of GEPs strength reduced");
-STATISTIC(NumInserted, "Number of PHIs inserted");
-STATISTIC(NumVariable, "Number of PHIs with variable strides");
+STATISTIC(NumReduced , "Number of GEPs strength reduced");
+STATISTIC(NumInserted, "Number of PHIs inserted");
+STATISTIC(NumVariable, "Number of PHIs with variable strides");
+STATISTIC(NumEliminated , "Number of strides eliminated");
namespace {
@@ -170,18 +171,17 @@
bool AddUsersIfInteresting(Instruction *I, Loop *L,
std::set<Instruction*> &Processed);
SCEVHandle GetExpressionSCEV(Instruction *E, Loop *L);
-
+ ICmpInst *ChangeCompareStride(Loop *L, ICmpInst *Cond,
+ IVStrideUse* &CondUse,
+ const SCEVHandle* &CondStride);
void OptimizeIndvars(Loop *L);
bool FindIVForUser(ICmpInst *Cond, IVStrideUse *&CondUse,
const SCEVHandle *&CondStride);
-
unsigned CheckForIVReuse(bool, const SCEVHandle&,
IVExpr&, const Type*,
const std::vector<BasedUser>& UsersToProcess);
-
bool ValidStride(bool, int64_t,
const std::vector<BasedUser>& UsersToProcess);
-
void StrengthReduceStridedIVUsers(const SCEVHandle &Stride,
IVUsersOfOneStride &Uses,
Loop *L, bool isOnlyStride);
@@ -981,8 +981,6 @@
const SCEVHandle &Stride,
IVExpr &IV, const Type *Ty,
const std::vector<BasedUser>& UsersToProcess) {
- if (!TLI) return 0;
-
if (SCEVConstant *SC = dyn_cast<SCEVConstant>(Stride)) {
int64_t SInt = SC->getValue()->getSExtValue();
if (SInt == 1) return 0;
@@ -1039,6 +1037,10 @@
IVUsersOfOneStride &Uses,
Loop *L,
bool isOnlyStride) {
+ // If all the users are moved to another stride, then there is nothing to do.
+ if (Uses.Users.size() == 0)
+ return;
+
// Transform our list of users and offsets to a bit more complex table. In
// this new vector, each 'BasedUser' contains 'Base' the base of the
// strided accessas well as the old information from Uses. We progressively
@@ -1377,6 +1379,154 @@
return false;
}
+namespace {
+ // Constant strides come first which in turns are sorted by their absolute
+ // values. If absolute values are the same, then positive strides comes first.
+ // e.g.
+ // 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
+ struct StrideCompare {
+ bool operator()(const SCEVHandle &LHS, const SCEVHandle &RHS) {
+ SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
+ SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
+ if (LHSC && RHSC) {
+ int64_t LV = LHSC->getValue()->getSExtValue();
+ int64_t RV = RHSC->getValue()->getSExtValue();
+ uint64_t ALV = (LV < 0) ? -LV : LV;
+ uint64_t ARV = (RV < 0) ? -RV : RV;
+ if (ALV == ARV)
+ return LV > RV;
+ else
+ return ALV < ARV;
+ }
+ return (LHSC && !RHSC);
+ }
+ };
+}
+
+/// ChangeCompareStride - If a loop termination compare instruction is the
+/// only use of its stride, and the compaison is against a constant value,
+/// try eliminate the stride by moving the compare instruction to another
+/// stride and change its constant operand accordingly. e.g.
+///
+/// loop:
+/// ...
+/// v1 = v1 + 3
+/// v2 = v2 + 1
+/// if (v2 < 10) goto loop
+/// =>
+/// loop:
+/// ...
+/// v1 = v1 + 3
+/// if (v1 < 30) goto loop
+ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
+ IVStrideUse* &CondUse,
+ const SCEVHandle* &CondStride) {
+ if (StrideOrder.size() < 2 ||
+ IVUsesByStride[*CondStride].Users.size() != 1)
+ return Cond;
+ // FIXME: loosen this restriction?
+ if (!isa<SCEVConstant>(CondUse->Offset))
+ return Cond;
+ const SCEVConstant *SC = dyn_cast<SCEVConstant>(*CondStride);
+ if (!SC) return Cond;
+ ConstantInt *C = dyn_cast<ConstantInt>(Cond->getOperand(1));
+ if (!C) return Cond;
+
+ ICmpInst::Predicate Predicate = Cond->getPredicate();
+ bool isSigned = ICmpInst::isSignedPredicate(Predicate);
+ int64_t CmpSSInt = SC->getValue()->getSExtValue();
+ int64_t CmpVal = C->getValue().getSExtValue();
+ uint64_t SignBit = 1ULL << (C->getValue().getBitWidth()-1);
+ int64_t NewCmpVal = CmpVal;
+ SCEVHandle *NewStride = NULL;
+ Value *NewIncV = NULL;
+ int64_t Scale = 1;
+ const Type *CmpTy = C->getType();
+ const Type *NewCmpTy = NULL;
+
+ // Look for a suitable stride / iv as replacement.
+ std::stable_sort(StrideOrder.begin(), StrideOrder.end(), StrideCompare());
+ for (unsigned i = 0, e = StrideOrder.size(); i != e; ++i) {
+ std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI =
+ IVUsesByStride.find(StrideOrder[i]);
+ if (!isa<SCEVConstant>(SI->first))
+ continue;
+ int64_t SSInt = cast<SCEVConstant>(SI->first)->getValue()->getSExtValue();
+ if (abs(SSInt) < abs(CmpSSInt) && (CmpSSInt % SSInt) == 0) {
+ Scale = CmpSSInt / SSInt;
+ NewCmpVal = CmpVal / Scale;
+ } else if (abs(SSInt) > abs(CmpSSInt) && (SSInt % CmpSSInt) == 0) {
+ Scale = SSInt / CmpSSInt;
+ NewCmpVal = CmpVal * Scale;
+ } else
+ continue;
+
+ // Watch out for overflow.
+ if (isSigned && (CmpVal & SignBit) != (NewCmpVal & SignBit))
+ NewCmpVal = CmpVal;
+ if (NewCmpVal != CmpVal) {
+ // Pick the best iv to use trying to avoid a cast.
+ NewIncV = NULL;
+ for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(),
+ E = SI->second.Users.end(); UI != E; ++UI) {
+ // if (!isa<SCEVConstant>(UI->Offset))
+ // continue;
+ NewIncV = UI->OperandValToReplace;
+ if (NewIncV->getType() == CmpTy)
+ break;
+ }
+ if (!NewIncV) {
+ NewCmpVal = CmpVal;
+ continue;
+ }
+
+ // FIXME: allow reuse of iv of a smaller type?
+ NewCmpTy = NewIncV->getType();
+ if (!CmpTy->canLosslesslyBitCastTo(NewCmpTy) &&
+ !(isa<PointerType>(NewCmpTy) &&
+ CmpTy->canLosslesslyBitCastTo(UIntPtrTy))) {
+ NewCmpVal = CmpVal;
+ continue;
+ }
+
+ // If scale is negative, use inverse predicate unless it's testing
+ // for equality.
+ if (Scale < 0 && !Cond->isEquality())
+ Predicate = ICmpInst::getInversePredicate(Predicate);
+
+ NewStride = &StrideOrder[i];
+ break;
+ }
+ }
+
+ if (NewCmpVal != CmpVal) {
+ // Create a new compare instruction using new stride / iv.
+ ICmpInst *OldCond = Cond;
+ Value *RHS = ConstantInt::get(C->getType(), NewCmpVal);
+ // Both sides of a ICmpInst must be of the same type.
+ if (NewCmpTy != CmpTy) {
+ if (isa<PointerType>(NewCmpTy) && !isa<PointerType>(CmpTy))
+ RHS= SCEVExpander::InsertCastOfTo(Instruction::IntToPtr, RHS, NewCmpTy);
+ else
+ RHS = SCEVExpander::InsertCastOfTo(Instruction::BitCast, RHS, NewCmpTy);
+ }
+ Cond = new ICmpInst(Predicate, NewIncV, RHS);
+ Cond->setName(L->getHeader()->getName() + ".termcond");
+ OldCond->getParent()->getInstList().insert(OldCond, Cond);
+ OldCond->replaceAllUsesWith(Cond);
+ OldCond->eraseFromParent();
+ IVUsesByStride[*CondStride].Users.pop_back();
+ SCEVHandle NewOffset = SE->getMulExpr(CondUse->Offset,
+ SE->getConstant(ConstantInt::get(CondUse->Offset->getType(), Scale)));
+ IVUsesByStride[*NewStride].addUser(NewOffset, Cond, NewIncV);
+ CondUse = &IVUsesByStride[*NewStride].Users.back();
+ CondStride = NewStride;
+ ++NumEliminated;
+ }
+
+ return Cond;
+}
+
// OptimizeIndvars - Now that IVUsesByStride is set up with all of the indvar
// uses in the loop, look to see if we can eliminate some, in favor of using
// common indvars for the different uses.
@@ -1403,7 +1553,10 @@
if (!FindIVForUser(Cond, CondUse, CondStride))
return; // setcc doesn't use the IV.
-
+
+ // If possible, change stride and operands of the compare instruction to
+ // eliminate one stride.
+ Cond = ChangeCompareStride(L, Cond, CondUse, CondStride);
// It's possible for the setcc instruction to be anywhere in the loop, and
// possible for it to have multiple users. If it is not immediately before
@@ -1431,30 +1584,6 @@
CondUse->isUseOfPostIncrementedValue = true;
}
-namespace {
- // Constant strides come first which in turns are sorted by their absolute
- // values. If absolute values are the same, then positive strides comes first.
- // e.g.
- // 4, -1, X, 1, 2 ==> 1, -1, 2, 4, X
- struct StrideCompare {
- bool operator()(const SCEVHandle &LHS, const SCEVHandle &RHS) {
- SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS);
- SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS);
- if (LHSC && RHSC) {
- int64_t LV = LHSC->getValue()->getSExtValue();
- int64_t RV = RHSC->getValue()->getSExtValue();
- uint64_t ALV = (LV < 0) ? -LV : LV;
- uint64_t ARV = (RV < 0) ? -RV : RV;
- if (ALV == ARV)
- return LV > RV;
- else
- return ALV < ARV;
- }
- return (LHSC && !RHSC);
- }
- };
-}
-
bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) {
LI = &getAnalysis<LoopInfo>();
Added: llvm/trunk/test/CodeGen/X86/loop-strength-reduce3.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/loop-strength-reduce3.ll?rev=43336&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/loop-strength-reduce3.ll (added)
+++ llvm/trunk/test/CodeGen/X86/loop-strength-reduce3.ll Thu Oct 25 04:11:16 2007
@@ -0,0 +1,37 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep cmp | grep 240
+; RUN: llvm-as < %s | llc -march=x86 | grep inc | count 1
+
+define i32 @foo(i32 %A, i32 %B, i32 %C, i32 %D) {
+entry:
+ %tmp2955 = icmp sgt i32 %C, 0 ; <i1> [#uses=1]
+ br i1 %tmp2955, label %bb26.outer.us, label %bb40.split
+
+bb26.outer.us: ; preds = %bb26.bb32_crit_edge.us, %entry
+ %i.044.0.ph.us = phi i32 [ 0, %entry ], [ %indvar.next57, %bb26.bb32_crit_edge.us ] ; <i32> [#uses=2]
+ %k.1.ph.us = phi i32 [ 0, %entry ], [ %k.0.us, %bb26.bb32_crit_edge.us ] ; <i32> [#uses=1]
+ %tmp3.us = mul i32 %i.044.0.ph.us, 6 ; <i32> [#uses=1]
+ br label %bb1.us
+
+bb1.us: ; preds = %bb1.us, %bb26.outer.us
+ %j.053.us = phi i32 [ 0, %bb26.outer.us ], [ %tmp25.us, %bb1.us ] ; <i32> [#uses=2]
+ %k.154.us = phi i32 [ %k.1.ph.us, %bb26.outer.us ], [ %k.0.us, %bb1.us ] ; <i32> [#uses=1]
+ %tmp5.us = add i32 %tmp3.us, %j.053.us ; <i32> [#uses=1]
+ %tmp7.us = shl i32 %D, %tmp5.us ; <i32> [#uses=2]
+ %tmp9.us = icmp eq i32 %tmp7.us, %B ; <i1> [#uses=1]
+ %tmp910.us = zext i1 %tmp9.us to i32 ; <i32> [#uses=1]
+ %tmp12.us = and i32 %tmp7.us, %A ; <i32> [#uses=1]
+ %tmp19.us = and i32 %tmp12.us, %tmp910.us ; <i32> [#uses=1]
+ %k.0.us = add i32 %tmp19.us, %k.154.us ; <i32> [#uses=3]
+ %tmp25.us = add i32 %j.053.us, 1 ; <i32> [#uses=2]
+ %tmp29.us = icmp slt i32 %tmp25.us, %C ; <i1> [#uses=1]
+ br i1 %tmp29.us, label %bb1.us, label %bb26.bb32_crit_edge.us
+
+bb26.bb32_crit_edge.us: ; preds = %bb1.us
+ %indvar.next57 = add i32 %i.044.0.ph.us, 1 ; <i32> [#uses=2]
+ %exitcond = icmp eq i32 %indvar.next57, 40 ; <i1> [#uses=1]
+ br i1 %exitcond, label %bb40.split, label %bb26.outer.us
+
+bb40.split: ; preds = %bb26.bb32_crit_edge.us, %entry
+ %k.1.lcssa.lcssa.us-lcssa = phi i32 [ %k.0.us, %bb26.bb32_crit_edge.us ], [ 0, %entry ] ; <i32> [#uses=1]
+ ret i32 %k.1.lcssa.lcssa.us-lcssa
+}
Added: llvm/trunk/test/CodeGen/X86/loop-strength-reduce4.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/loop-strength-reduce4.ll?rev=43336&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/loop-strength-reduce4.ll (added)
+++ llvm/trunk/test/CodeGen/X86/loop-strength-reduce4.ll Thu Oct 25 04:11:16 2007
@@ -0,0 +1,49 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep cmp | grep 64
+; RUN: llvm-as < %s | llc -march=x86 | not grep inc
+
+ at state = external global [0 x i32] ; <[0 x i32]*> [#uses=4]
+ at S = external global [0 x i32] ; <[0 x i32]*> [#uses=4]
+
+define i32 @foo() {
+entry:
+ br label %bb
+
+bb: ; preds = %bb, %entry
+ %indvar = phi i32 [ 0, %entry ], [ %indvar.next, %bb ] ; <i32> [#uses=2]
+ %t.063.0 = phi i32 [ 0, %entry ], [ %tmp47, %bb ] ; <i32> [#uses=1]
+ %j.065.0 = shl i32 %indvar, 2 ; <i32> [#uses=4]
+ %tmp3 = getelementptr [0 x i32]* @state, i32 0, i32 %j.065.0 ; <i32*> [#uses=2]
+ %tmp4 = load i32* %tmp3, align 4 ; <i32> [#uses=1]
+ %tmp6 = getelementptr [0 x i32]* @S, i32 0, i32 %t.063.0 ; <i32*> [#uses=1]
+ %tmp7 = load i32* %tmp6, align 4 ; <i32> [#uses=1]
+ %tmp8 = xor i32 %tmp7, %tmp4 ; <i32> [#uses=2]
+ store i32 %tmp8, i32* %tmp3, align 4
+ %tmp1378 = or i32 %j.065.0, 1 ; <i32> [#uses=1]
+ %tmp16 = getelementptr [0 x i32]* @state, i32 0, i32 %tmp1378 ; <i32*> [#uses=2]
+ %tmp17 = load i32* %tmp16, align 4 ; <i32> [#uses=1]
+ %tmp19 = getelementptr [0 x i32]* @S, i32 0, i32 %tmp8 ; <i32*> [#uses=1]
+ %tmp20 = load i32* %tmp19, align 4 ; <i32> [#uses=1]
+ %tmp21 = xor i32 %tmp20, %tmp17 ; <i32> [#uses=2]
+ store i32 %tmp21, i32* %tmp16, align 4
+ %tmp2680 = or i32 %j.065.0, 2 ; <i32> [#uses=1]
+ %tmp29 = getelementptr [0 x i32]* @state, i32 0, i32 %tmp2680 ; <i32*> [#uses=2]
+ %tmp30 = load i32* %tmp29, align 4 ; <i32> [#uses=1]
+ %tmp32 = getelementptr [0 x i32]* @S, i32 0, i32 %tmp21 ; <i32*> [#uses=1]
+ %tmp33 = load i32* %tmp32, align 4 ; <i32> [#uses=1]
+ %tmp34 = xor i32 %tmp33, %tmp30 ; <i32> [#uses=2]
+ store i32 %tmp34, i32* %tmp29, align 4
+ %tmp3982 = or i32 %j.065.0, 3 ; <i32> [#uses=1]
+ %tmp42 = getelementptr [0 x i32]* @state, i32 0, i32 %tmp3982 ; <i32*> [#uses=2]
+ %tmp43 = load i32* %tmp42, align 4 ; <i32> [#uses=1]
+ %tmp45 = getelementptr [0 x i32]* @S, i32 0, i32 %tmp34 ; <i32*> [#uses=1]
+ %tmp46 = load i32* %tmp45, align 4 ; <i32> [#uses=1]
+ %tmp47 = xor i32 %tmp46, %tmp43 ; <i32> [#uses=3]
+ store i32 %tmp47, i32* %tmp42, align 4
+ %indvar.next = add i32 %indvar, 1 ; <i32> [#uses=2]
+ %exitcond = icmp eq i32 %indvar.next, 4 ; <i1> [#uses=1]
+ br i1 %exitcond, label %bb57, label %bb
+
+bb57: ; preds = %bb
+ %tmp59 = and i32 %tmp47, 255 ; <i32> [#uses=1]
+ ret i32 %tmp59
+}
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