[llvm-commits] [llvm] r132103 - in /llvm/trunk: lib/Transforms/Scalar/IndVarSimplify.cpp test/Transforms/IndVarSimplify/elim-extend.ll
Andrew Trick
atrick at apple.com
Wed May 25 17:46:11 PDT 2011
Author: atrick
Date: Wed May 25 19:46:11 2011
New Revision: 132103
URL: http://llvm.org/viewvc/llvm-project?rev=132103&view=rev
Log:
indvars: incremental fixes for -disable-iv-rewrite and testcases.
Use a proper worklist for use-def traversal without holding onto an
iterator. Now that we process all IV uses, we need complete logic for
resusing existing derived IV defs. See HoistStep.
Modified:
llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
llvm/trunk/test/Transforms/IndVarSimplify/elim-extend.ll
Modified: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp?rev=132103&r1=132102&r2=132103&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp Wed May 25 19:46:11 2011
@@ -537,6 +537,7 @@
LoopInfo *LI;
Loop *L;
ScalarEvolution *SE;
+ DominatorTree *DT;
SmallVectorImpl<WeakVH> &DeadInsts;
PHINode *WidePhi;
@@ -547,7 +548,8 @@
public:
WidenIV(PHINode *PN, const WideIVInfo &IVInfo, IVUsers *IUsers,
- LoopInfo *LInfo, ScalarEvolution *SEv, SmallVectorImpl<WeakVH> &DI) :
+ LoopInfo *LInfo, ScalarEvolution *SEv, DominatorTree *DTree,
+ SmallVectorImpl<WeakVH> &DI) :
OrigPhi(PN),
WideType(IVInfo.WidestNativeType),
IsSigned(IVInfo.IsSigned),
@@ -555,6 +557,7 @@
LI(LInfo),
L(LI->getLoopFor(OrigPhi->getParent())),
SE(SEv),
+ DT(DTree),
DeadInsts(DI),
WidePhi(0),
WideInc(0),
@@ -616,7 +619,7 @@
}
for (WideIVMap::const_iterator I = IVMap.begin(), E = IVMap.end();
I != E; ++I) {
- WidenIV Widener(I->first, I->second, IU, LI, SE, DeadInsts);
+ WidenIV Widener(I->first, I->second, IU, LI, SE, DT, DeadInsts);
if (Widener.CreateWideIV(Rewriter))
Changed = true;
}
@@ -696,6 +699,40 @@
return AddRec;
}
+/// HoistStep - Attempt to hoist an IV increment above a potential use.
+///
+/// To successfully hoist, two criteria must be met:
+/// - IncV operands dominate InsertPos and
+/// - InsertPos dominates IncV
+///
+/// Meeting the second condition means that we don't need to check all of IncV's
+/// existing uses (it's moving up in the domtree).
+///
+/// This does not yet recursively hoist the operands, although that would
+/// not be difficult.
+static bool HoistStep(Instruction *IncV, Instruction *InsertPos,
+ const DominatorTree *DT)
+{
+ if (DT->dominates(IncV, InsertPos))
+ return true;
+
+ if (!DT->dominates(InsertPos->getParent(), IncV->getParent()))
+ return false;
+
+ if (IncV->mayHaveSideEffects())
+ return false;
+
+ // Attempt to hoist IncV
+ for (User::op_iterator OI = IncV->op_begin(), OE = IncV->op_end();
+ OI != OE; ++OI) {
+ Instruction *OInst = dyn_cast<Instruction>(OI);
+ if (OInst && !DT->dominates(OInst, InsertPos))
+ return false;
+ }
+ IncV->moveBefore(InsertPos);
+ return true;
+}
+
/// WidenIVUse - Determine whether an individual user of the narrow IV can be
/// widened. If so, return the wide clone of the user.
Instruction *WidenIV::WidenIVUse(Instruction *NarrowUse,
@@ -755,9 +792,10 @@
NarrowUse->replaceUsesOfWith(NarrowDef, Trunc);
return 0;
}
+ // Reuse the IV increment that SCEVExpander created as long as it dominates
+ // NarrowUse.
Instruction *WideUse = 0;
- if (WideAddRec == WideIncExpr) {
- // Reuse the IV increment that SCEVExpander created.
+ if (WideAddRec == WideIncExpr && HoistStep(WideInc, NarrowUse, DT)) {
WideUse = WideInc;
}
else {
@@ -828,32 +866,45 @@
// WidenIVUse to reuse it when widening the narrow IV's increment. We don't
// employ a general reuse mechanism because the call above is the only call to
// SCEVExpander. Henceforth, we produce 1-to-1 narrow to wide uses.
- assert(WidePhi->hasOneUse() && "New IV has multiple users");
- WideInc = WidePhi->use_back();
- WideIncExpr = SE->getSCEV(WideInc);
+ if (BasicBlock *LatchBlock = L->getLoopLatch()) {
+ WideInc =
+ cast<Instruction>(WidePhi->getIncomingValueForBlock(LatchBlock));
+ WideIncExpr = SE->getSCEV(WideInc);
+ }
DEBUG(dbgs() << "Wide IV: " << *WidePhi << "\n");
++NumWidened;
// Traverse the def-use chain using a worklist starting at the original IV.
assert(Processed.empty() && "expect initial state" );
- SmallVector<std::pair<Instruction *, Instruction *>, 8> NarrowIVUsers;
- NarrowIVUsers.push_back(std::make_pair(OrigPhi, WidePhi));
+ // Each worklist entry has a Narrow def-use link and Wide def.
+ SmallVector<std::pair<Use *, Instruction *>, 8> NarrowIVUsers;
+ for (Value::use_iterator UI = OrigPhi->use_begin(),
+ UE = OrigPhi->use_end(); UI != UE; ++UI) {
+ NarrowIVUsers.push_back(std::make_pair(&UI.getUse(), WidePhi));
+ }
while (!NarrowIVUsers.empty()) {
- Instruction *NarrowInst, *WideInst;
- tie(NarrowInst, WideInst) = NarrowIVUsers.pop_back_val();
-
- for (Value::use_iterator UI = NarrowInst->use_begin(),
- UE = NarrowInst->use_end(); UI != UE; ++UI) {
- Instruction *NarrowUse = cast<Instruction>(*UI);
- Instruction *WideUse = WidenIVUse(NarrowUse, NarrowInst, WideInst);
- if (WideUse)
- NarrowIVUsers.push_back(std::make_pair(NarrowUse, WideUse));
-
- if (NarrowInst->use_empty())
- DeadInsts.push_back(NarrowInst);
+ Use *NarrowDefUse;
+ Instruction *WideDef;
+ tie(NarrowDefUse, WideDef) = NarrowIVUsers.pop_back_val();
+
+ // Process a def-use edge. This may replace the use, so don't hold a
+ // use_iterator across it.
+ Instruction *NarrowDef = cast<Instruction>(NarrowDefUse->get());
+ Instruction *NarrowUse = cast<Instruction>(NarrowDefUse->getUser());
+ Instruction *WideUse = WidenIVUse(NarrowUse, NarrowDef, WideDef);
+
+ // Follow all def-use edges from the previous narrow use.
+ if (WideUse) {
+ for (Value::use_iterator UI = NarrowUse->use_begin(),
+ UE = NarrowUse->use_end(); UI != UE; ++UI) {
+ NarrowIVUsers.push_back(std::make_pair(&UI.getUse(), WideUse));
+ }
}
+ // WidenIVUse may have removed the def-use edge.
+ if (NarrowDef->use_empty())
+ DeadInsts.push_back(NarrowDef);
}
return true;
}
Modified: llvm/trunk/test/Transforms/IndVarSimplify/elim-extend.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/elim-extend.ll?rev=132103&r1=132102&r2=132103&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/elim-extend.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/elim-extend.ll Wed May 25 19:46:11 2011
@@ -2,7 +2,72 @@
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-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
-; Tests sign extend elimination in the inner and outer loop.
+; Test reusing the same IV with constant start for preinc and postinc values
+; with and without NSW.
+; IV rewrite only removes one sext. WidenIVs should remove all three.
+define void @postincConstIV(i8* %base, i32 %limit) nounwind {
+entry:
+ br label %loop
+; CHECK: loop:
+; CHECK-NOT: sext
+; CHECK: exit:
+loop:
+ %iv = phi i32 [ %postiv, %loop ], [ 0, %entry ]
+ %ivnsw = phi i32 [ %postivnsw, %loop ], [ 0, %entry ]
+ %preofs = sext i32 %iv to i64
+ %preadr = getelementptr i8* %base, i64 %preofs
+ store i8 0, i8* %preadr
+ %postiv = add i32 %iv, 1
+ %postofs = sext i32 %postiv to i64
+ %postadr = getelementptr i8* %base, i64 %postofs
+ store i8 0, i8* %postadr
+ %postivnsw = add nsw i32 %ivnsw, 1
+ %postofsnsw = sext i32 %postivnsw to i64
+ %postadrnsw = getelementptr i8* %base, i64 %postofsnsw
+ store i8 0, i8* %postadrnsw
+ %cond = icmp sgt i32 %limit, %iv
+ br i1 %cond, label %loop, label %exit
+exit:
+ br label %return
+return:
+ ret void
+}
+
+; Test reusing the same IV with nonconstant start for preinc and postinc values
+; with and without NSW.
+; As with constant IV start, WidenIVs should remove all three.
+;
+; FIXME: WidenIVs should remove %postofs just like %postofsnsw
+define void @postincVarIV(i8* %base, i32 %init, i32 %limit) nounwind {
+entry:
+ br label %loop
+; CHECK: loop:
+; CHECK: sext
+; CHECK-NOT: sext
+; CHECK: exit:
+loop:
+ %iv = phi i32 [ %postiv, %loop ], [ %init, %entry ]
+ %ivnsw = phi i32 [ %postivnsw, %loop ], [ 0, %entry ]
+ %preofs = sext i32 %iv to i64
+ %preadr = getelementptr i8* %base, i64 %preofs
+ store i8 0, i8* %preadr
+ %postiv = add i32 %iv, 1
+ %postofs = sext i32 %postiv to i64
+ %postadr = getelementptr i8* %base, i64 %postofs
+ store i8 0, i8* %postadr
+ %postivnsw = add nsw i32 %ivnsw, 1
+ %postofsnsw = sext i32 %postivnsw to i64
+ %postadrnsw = getelementptr i8* %base, i64 %postofsnsw
+ store i8 0, i8* %postadrnsw
+ %cond = icmp sgt i32 %limit, %iv
+ br i1 %cond, label %loop, label %exit
+exit:
+ br label %return
+return:
+ ret void
+}
+
+; Test sign extend elimination in the inner and outer loop.
; %outercount is straightforward to widen, besides being in an outer loop.
; %innercount is currently blocked by lcssa, so is not widened.
; %inneriv can be widened only after proving it has no signed-overflow
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