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The logic inside getMulExpr to simplify {a,+,b}*{c,+,d} was wrong, which was 

visible given a=b=c=d=1, on iteration #1 (the second iteration). Replace it with
correct math. Fixes PR10383!

llvm-svn: 139133
This commit is contained in:
Nick Lewycky 2011-09-06 05:05:14 +00:00
parent 3ab15558d7
commit 658bdb5133
2 changed files with 54 additions and 16 deletions
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33
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -1735,7 +1735,7 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
// If all of the other operands were loop invariant, we are done.
if (Ops.size() == 1) return NewRec;
// Otherwise, add the folded AddRec by the non-liv parts.
// Otherwise, add the folded AddRec by the non-live parts.
for (unsigned i = 0;; ++i)
if (Ops[i] == AddRec) {
Ops[i] = NewRec;
@ -1960,7 +1960,7 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
// If all of the other operands were loop invariant, we are done.
if (Ops.size() == 1) return NewRec;
// Otherwise, multiply the folded AddRec by the non-liv parts.
// Otherwise, multiply the folded AddRec by the non-live parts.
for (unsigned i = 0;; ++i)
if (Ops[i] == AddRec) {
Ops[i] = NewRec;
@ -1976,22 +1976,29 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
++OtherIdx)
if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
// F * G, where F = {A,+,B}<L> and G = {C,+,D}<L> -->
// {A*C,+,F*D + G*B + B*D}<L>
// {A,+,B}<L> * {C,+,D}<L> --> {A*C,+,A*D + B*C + B*D,+,2*B*D}<L>
for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
++OtherIdx)
if (const SCEVAddRecExpr *OtherAddRec =
dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
if (OtherAddRec->getLoop() == AddRecLoop) {
const SCEVAddRecExpr *F = AddRec, *G = OtherAddRec;
const SCEV *NewStart = getMulExpr(F->getStart(), G->getStart());
const SCEV *B = F->getStepRecurrence(*this);
const SCEV *D = G->getStepRecurrence(*this);
const SCEV *NewStep = getAddExpr(getMulExpr(F, D),
getMulExpr(G, B),
getMulExpr(B, D));
const SCEV *NewAddRec = getAddRecExpr(NewStart, NewStep,
F->getLoop(),
const SCEV *A = AddRec->getStart();
const SCEV *B = AddRec->getStepRecurrence(*this);
const SCEV *C = OtherAddRec->getStart();
const SCEV *D = OtherAddRec->getStepRecurrence(*this);
const SCEV *NewStart = getMulExpr(A, C);
const SCEV *BD = getMulExpr(B, D);
const SCEV *NewStep = getAddExpr(getMulExpr(A, D),
getMulExpr(B, C), BD);
const SCEV *NewSecondOrderStep =
getMulExpr(BD, getConstant(BD->getType(), 2));
SmallVector<const SCEV *, 3> AddRecOps;
AddRecOps.push_back(NewStart);
AddRecOps.push_back(NewStep);
AddRecOps.push_back(NewSecondOrderStep);
const SCEV *NewAddRec = getAddRecExpr(AddRecOps,
AddRec->getLoop(),
SCEV::FlagAnyWrap);
if (Ops.size() == 2) return NewAddRec;
Ops[Idx] = AddRec = cast<SCEVAddRecExpr>(NewAddRec);

37
llvm/test/Analysis/ScalarEvolution/SolveQuadraticEquation.ll
View File

@ -1,11 +1,11 @@
; RUN: opt < %s -analyze -scalar-evolution \
; RUN: -scalar-evolution-max-iterations=0 | grep {backedge-taken count is 100}
; RUN: -scalar-evolution-max-iterations=0 | FileCheck %s
; PR1101
@A = weak global [1000 x i32] zeroinitializer, align 32
define void @test(i32 %N) {
define void @test1(i32 %N) {
entry:
%"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
br label %bb3
@ -30,3 +30,34 @@ bb5: ; preds = %bb3
return: ; preds = %bb5
ret void
}
; CHECK: Determining loop execution counts for: @test1
; CHECK-NEXT: backedge-taken count is 100
; PR10383
; This used to crash.
define void @test2(i1 %cmp, i64 %n) {
entry:
br label %for.body1
for.body1:
%a0.08 = phi i64 [ 0, %entry ], [ %inc512, %for.body1 ]
%inc512 = add i64 %a0.08, 1
br i1 %cmp, label %preheader, label %for.body1
preheader:
br label %for.body2
for.body2:
%indvar = phi i64 [ 0, %preheader ], [ %indvar.next, %for.body2 ]
%tmp111 = add i64 %n, %indvar
%tmp114 = mul i64 %a0.08, %indvar
%mul542 = mul i64 %tmp114, %tmp111
%indvar.next = add i64 %indvar, 1
br i1 undef, label %end, label %for.body2
end:
ret void
}
; CHECK: Determining loop execution counts for: @test2