[polly] r255471 - Always treat scalar writes as MUST_WRITEs
Johannes Doerfert via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 14 00:52:15 PST 2015
On 12/14, Michael Kruse wrote:
> 2015-12-14 8:59 GMT+01:00 Johannes Doerfert <doerfert at cs.uni-saarland.de>:
> > What about a case like this:
> >
> > b0:
> > br %non_affine %b1, %b2
> >
> > b1:
> > x = ..
> > br %b3
> >
> > b2:
> > y = ...
> > br %b3
> >
> > b3:
> > z = phi [b1, x], [b2, y]
> >
> > shouldn't the phiops write accesses to x and y be MAY_WRITEs in the
> > non-affine region b0-b3 ?
> >
> > I don't think it matters much but I since we try to model it right now I
> > wanted to ask.
>
> They are not modelled at all because they are used only within the
> non-affine subregion. x and y cannot be used after and including b3
> because b3 is not dominated by either b1 or b2. There is also no
> "phiops" write to x nor y because these are not PHI nodes.
>
> If you think about the two PHI WRITE accesses ("at" br %b3), They will
> be collapsed to one MustWriteAccess in DependenceInfo for the whole
> statement.
I'm talking about the modeling in the SCoP here. Are these two accesses
may or must accesses? In the former case I don't see how they are
collapsed, in the latter I wonder if that is what we want. My initial
comment aimed at the latter case, thus that we now model the phiops
write access as must and not may.
> The z.phiops will be written by one of the PHI WRITEs,
> leaving no possibility that the write could be only conditional.
> Otherwise the IR would not be well-formed.
>
> Hope this addresses your concerns.
>
> Michael
>
>
> > On 12/13, Michael Kruse via llvm-commits wrote:
> >> Author: meinersbur
> >> Date: Sun Dec 13 16:10:32 2015
> >> New Revision: 255471
> >>
> >> URL: http://llvm.org/viewvc/llvm-project?rev=255471&view=rev
> >> Log:
> >> Always treat scalar writes as MUST_WRITEs
> >>
> >> LLVM's IR guarantees that a value definition occurs before any use, and
> >> also the value of a PHI must be one of the incoming values, "written"
> >> in one of the incoming blocks. Hence, such writes are never conditional
> >> in the context of a non-affine subregion.
> >>
> >> Modified:
> >> polly/trunk/lib/Analysis/ScopInfo.cpp
> >> polly/trunk/test/ScopInfo/NonAffine/non_affine_loop_used_later.ll
> >> polly/trunk/test/ScopInfo/intra-non-affine-stmt-phi-node.ll
> >> polly/trunk/test/ScopInfo/non_affine_region_2.ll
> >> polly/trunk/test/ScopInfo/non_affine_region_3.ll
> >> polly/trunk/test/ScopInfo/non_affine_region_4.ll
> >>
> >> Modified: polly/trunk/lib/Analysis/ScopInfo.cpp
> >> URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/Analysis/ScopInfo.cpp?rev=255471&r1=255470&r2=255471&view=diff
> >> ==============================================================================
> >> --- polly/trunk/lib/Analysis/ScopInfo.cpp (original)
> >> +++ polly/trunk/lib/Analysis/ScopInfo.cpp Sun Dec 13 16:10:32 2015
> >> @@ -3885,8 +3885,12 @@ void ScopInfo::addMemoryAccess(BasicBloc
> >> Value *BaseAddr = BaseAddress;
> >> std::string BaseName = getIslCompatibleName("MemRef_", BaseAddr, "");
> >>
> >> - bool isApproximated =
> >> - Stmt->isRegionStmt() && (Stmt->getRegion()->getEntry() != BB);
> >> + // The execution of a store is not guaranteed if not in the entry block of a
> >> + // subregion. However, scalar writes (llvm::Value definitions or one of a
> >> + // PHI's incoming values) must occur in well-formed IR code.
> >> + bool isApproximated = (Kind == ScopArrayInfo::MK_Array) &&
> >> + Stmt->isRegionStmt() &&
> >> + (Stmt->getRegion()->getEntry() != BB);
> >> if (isApproximated && Type == MemoryAccess::MUST_WRITE)
> >> Type = MemoryAccess::MAY_WRITE;
> >>
> >>
> >> Modified: polly/trunk/test/ScopInfo/NonAffine/non_affine_loop_used_later.ll
> >> URL: http://llvm.org/viewvc/llvm-project/polly/trunk/test/ScopInfo/NonAffine/non_affine_loop_used_later.ll?rev=255471&r1=255470&r2=255471&view=diff
> >> ==============================================================================
> >> --- polly/trunk/test/ScopInfo/NonAffine/non_affine_loop_used_later.ll (original)
> >> +++ polly/trunk/test/ScopInfo/NonAffine/non_affine_loop_used_later.ll Sun Dec 13 16:10:32 2015
> >> @@ -39,7 +39,7 @@
> >> ; CHECK: [N] -> { Stmt_bb4__TO__bb18[i0] -> MemRef_A[i0] };
> >> ; CHECK: ReadAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK: [N] -> { Stmt_bb4__TO__bb18[i0] -> MemRef_smax[] };
> >> -; CHECK: MayWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> +; CHECK: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK: [N] -> { Stmt_bb4__TO__bb18[i0] -> MemRef_j_2__phi[] };
> >> ; CHECK: ReadAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK: [N] -> { Stmt_bb4__TO__bb18[i0] -> MemRef_j_0[] };
> >>
> >> Modified: polly/trunk/test/ScopInfo/intra-non-affine-stmt-phi-node.ll
> >> URL: http://llvm.org/viewvc/llvm-project/polly/trunk/test/ScopInfo/intra-non-affine-stmt-phi-node.ll?rev=255471&r1=255470&r2=255471&view=diff
> >> ==============================================================================
> >> --- polly/trunk/test/ScopInfo/intra-non-affine-stmt-phi-node.ll (original)
> >> +++ polly/trunk/test/ScopInfo/intra-non-affine-stmt-phi-node.ll Sun Dec 13 16:10:32 2015
> >> @@ -10,9 +10,9 @@
> >> ; CHECK-NEXT: { Stmt_loop__TO__backedge[i0] -> [i0, 0] };
> >> ; CHECK-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK-NEXT: { Stmt_loop__TO__backedge[i0] -> MemRef_merge__phi[] };
> >> -; CHECK-NEXT: MayWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> +; CHECK-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK-NEXT: { Stmt_loop__TO__backedge[i0] -> MemRef_merge__phi[] };
> >> -; CHECK-NEXT: MayWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> +; CHECK-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK-NEXT: { Stmt_loop__TO__backedge[i0] -> MemRef_merge__phi[] };
> >> ; CHECK-NEXT: Stmt_backedge
> >> ; CHECK-NEXT: Domain :=
> >>
> >> Modified: polly/trunk/test/ScopInfo/non_affine_region_2.ll
> >> URL: http://llvm.org/viewvc/llvm-project/polly/trunk/test/ScopInfo/non_affine_region_2.ll?rev=255471&r1=255470&r2=255471&view=diff
> >> ==============================================================================
> >> --- polly/trunk/test/ScopInfo/non_affine_region_2.ll (original)
> >> +++ polly/trunk/test/ScopInfo/non_affine_region_2.ll Sun Dec 13 16:10:32 2015
> >> @@ -35,7 +35,7 @@
> >> ; CHECK-NEXT: { Stmt_bb3__TO__bb18[i0] -> MemRef_A[i0] };
> >> ; CHECK-NOT: { Stmt_bb3__TO__bb18[i0] -> MemRef_x_0[] };
> >> ; CHECK-NOT: { Stmt_bb3__TO__bb18[i0] -> MemRef_x_1[] };
> >> -; CHECK: MayWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> +; CHECK: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK-NEXT: { Stmt_bb3__TO__bb18[i0] -> MemRef_x_2__phi[] };
> >> ; CHECK-NOT: { Stmt_bb3__TO__bb18[i0] -> MemRef_x_0[] };
> >> ; CHECK-NOT: { Stmt_bb3__TO__bb18[i0] -> MemRef_x_1[] };
> >>
> >> Modified: polly/trunk/test/ScopInfo/non_affine_region_3.ll
> >> URL: http://llvm.org/viewvc/llvm-project/polly/trunk/test/ScopInfo/non_affine_region_3.ll?rev=255471&r1=255470&r2=255471&view=diff
> >> ==============================================================================
> >> --- polly/trunk/test/ScopInfo/non_affine_region_3.ll (original)
> >> +++ polly/trunk/test/ScopInfo/non_affine_region_3.ll Sun Dec 13 16:10:32 2015
> >> @@ -31,11 +31,11 @@
> >> ; CHECK: { Stmt_bb3__TO__bb18[i0] -> [i0, 0] };
> >> ; CHECK: ReadAccess := [Reduction Type: NONE] [Scalar: 0]
> >> ; CHECK: { Stmt_bb3__TO__bb18[i0] -> MemRef_A[i0] };
> >> -; CHECK: MayWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> +; CHECK: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK: { Stmt_bb3__TO__bb18[i0] -> MemRef_x_2__phi[] };
> >> -; CHECK: MayWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> +; CHECK: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK: { Stmt_bb3__TO__bb18[i0] -> MemRef_x_2__phi[] };
> >> -; CHECK: MayWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> +; CHECK: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK: { Stmt_bb3__TO__bb18[i0] -> MemRef_x_2__phi[] };
> >> ; CHECK: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK: { Stmt_bb3__TO__bb18[i0] -> MemRef_x_2__phi[] };
> >>
> >> Modified: polly/trunk/test/ScopInfo/non_affine_region_4.ll
> >> URL: http://llvm.org/viewvc/llvm-project/polly/trunk/test/ScopInfo/non_affine_region_4.ll?rev=255471&r1=255470&r2=255471&view=diff
> >> ==============================================================================
> >> --- polly/trunk/test/ScopInfo/non_affine_region_4.ll (original)
> >> +++ polly/trunk/test/ScopInfo/non_affine_region_4.ll Sun Dec 13 16:10:32 2015
> >> @@ -39,7 +39,7 @@
> >> ; CHECK: { Stmt_bb2__TO__bb7[i0] -> MemRef_A[i0] };
> >> ; CHECK: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK: { Stmt_bb2__TO__bb7[i0] -> MemRef_x[] };
> >> -; CHECK: MayWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> +; CHECK: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK: { Stmt_bb2__TO__bb7[i0] -> MemRef_y__phi[] };
> >> ; CHECK: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
> >> ; CHECK: { Stmt_bb2__TO__bb7[i0] -> MemRef_y__phi[] };
> >>
> >>
> >> _______________________________________________
> >> llvm-commits mailing list
> >> llvm-commits at lists.llvm.org
> >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
> >
> > --
> >
> > Johannes Doerfert
> > Researcher / PhD Student
> >
> > Compiler Design Lab (Prof. Hack)
> > Saarland University, Computer Science
> > Building E1.3, Room 4.31
> >
> > Tel. +49 (0)681 302-57521 : doerfert at cs.uni-saarland.de
> > Fax. +49 (0)681 302-3065 : http://www.cdl.uni-saarland.de/people/doerfert
--
Johannes Doerfert
Researcher / PhD Student
Compiler Design Lab (Prof. Hack)
Saarland University, Computer Science
Building E1.3, Room 4.31
Tel. +49 (0)681 302-57521 : doerfert at cs.uni-saarland.de
Fax. +49 (0)681 302-3065 : http://www.cdl.uni-saarland.de/people/doerfert
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