[llvm] r257795 - [SROA] Also insert a bit piece expression if only one piece is needed
James Molloy via llvm-commits
llvm-commits at lists.llvm.org
Mon Aug 15 02:52:20 PDT 2016
Hi Keno, Adrian,
A recent change of mine to SimplifyCFG exposed a bug in this commit. This
assert is firing:
assert(Pieces.size() == 1 &&
"partition is as large as original alloca");
>From the phab review it looks like this assert was added in late in the
review process and my testing shows that this assert is never tested at all
in the regression tests (changing to assert(0) doesn't cause any failures!)
The error is shown here:
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-autoconf/builds/23920/steps/annotate/logs/stdio
It's easily reproducible with ToT clang simply compiling the
file projects/compiler-rt/lib/builtins/powixf2.c *with debug info enabled
(-g)*.
I'd fix it myself but after staring for a while I can't work out if the the
assert sense is wrong (the text "partition is as large as original alloca"
seems like a failure mode to me, which would indicate that perhaps the test
should have been "Pieces.size() != 1" ?) or if the assert is correct but
there is a failure somewhere else.
Could you please take a look?
Cheers,
James
On Thu, 14 Jan 2016 at 20:10 Keno Fischer via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: kfischer
> Date: Thu Jan 14 14:06:34 2016
> New Revision: 257795
>
> URL: http://llvm.org/viewvc/llvm-project?rev=257795&view=rev
> Log:
> [SROA] Also insert a bit piece expression if only one piece is needed
>
> Summary: If SROA creates only one piece (e.g. because the other is not
> needed),
> it still needs to create a bit_piece expression if that bit piece is
> smaller
> than the original size of the alloca.
>
> Reviewers: aprantl
>
> Subscribers: llvm-commits
>
> Differential Revision: http://reviews.llvm.org/D16187
>
> Added:
> llvm/trunk/test/Transforms/SROA/dbg-single-piece.ll
> Modified:
> llvm/trunk/lib/Transforms/Scalar/SROA.cpp
>
> Modified: llvm/trunk/lib/Transforms/Scalar/SROA.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SROA.cpp?rev=257795&r1=257794&r2=257795&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/SROA.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/SROA.cpp Thu Jan 14 14:06:34 2016
> @@ -4024,12 +4024,12 @@ bool SROA::splitAlloca(AllocaInst &AI, A
> auto *Var = DbgDecl->getVariable();
> auto *Expr = DbgDecl->getExpression();
> DIBuilder DIB(*AI.getModule(), /*AllowUnresolved*/ false);
> - bool IsSplit = Pieces.size() > 1;
> + uint64_t AllocaSize = DL.getTypeSizeInBits(AI.getAllocatedType());
> for (auto Piece : Pieces) {
> // Create a piece expression describing the new partition or reuse
> AI's
> // expression if there is only one partition.
> auto *PieceExpr = Expr;
> - if (IsSplit || Expr->isBitPiece()) {
> + if (Piece.Size < AllocaSize || Expr->isBitPiece()) {
> // If this alloca is already a scalar replacement of a larger
> aggregate,
> // Piece.Offset describes the offset inside the scalar.
> uint64_t Offset = Expr->isBitPiece() ? Expr->getBitPieceOffset()
> : 0;
> @@ -4043,6 +4043,9 @@ bool SROA::splitAlloca(AllocaInst &AI, A
> Size = std::min(Size, AbsEnd - Start);
> }
> PieceExpr = DIB.createBitPieceExpression(Start, Size);
> + } else {
> + assert(Pieces.size() == 1 &&
> + "partition is as large as original alloca");
> }
>
> // Remove any existing dbg.declare intrinsic describing the same
> alloca.
>
> Added: llvm/trunk/test/Transforms/SROA/dbg-single-piece.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SROA/dbg-single-piece.ll?rev=257795&view=auto
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/SROA/dbg-single-piece.ll (added)
> +++ llvm/trunk/test/Transforms/SROA/dbg-single-piece.ll Thu Jan 14
> 14:06:34 2016
> @@ -0,0 +1,37 @@
> +; RUN: opt -sroa %s -S | FileCheck %s
> +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> +
> +%foo = type { [8 x i8], [8 x i8] }
> +
> +declare void @llvm.dbg.declare(metadata, metadata, metadata) #0
> +define void
> @_ZL18findInsertLocationPN4llvm17MachineBasicBlockENS_9SlotIndexERNS_13LiveIntervalsE()
> {
> +entry:
> + %retval = alloca %foo, align 8
> + call void @llvm.dbg.declare(metadata %foo* %retval, metadata !1,
> metadata !7), !dbg !8
> +; Checks that SROA still inserts a bit_piece expression, even if it
> produces only one piece
> +; (as long as that piece is smaller than the whole thing)
> +; CHECK-NOT: call void @llvm.dbg.value
> +; CHECK: call void @llvm.dbg.value(metadata %foo* undef, i64 0, metadata
> !1, metadata ![[BIT_PIECE:[0-9]+]]), !dbg
> +; CHECK-NOT: call void @llvm.dbg.value
> +; CHECK: ![[BIT_PIECE]] = !DIExpression(DW_OP_bit_piece, 64, 64)
> + %0 = bitcast %foo* %retval to i8*
> + %1 = getelementptr inbounds i8, i8* %0, i64 8
> + %2 = bitcast i8* %1 to %foo**
> + store %foo* undef, %foo** %2, align 8
> + ret void
> +}
> +
> +attributes #0 = { nounwind readnone }
> +
> +!llvm.dbg.cu = !{}
> +!llvm.module.flags = !{!0}
> +
> +!0 = !{i32 2, !"Debug Info Version", i32 3}
> +!1 = !DILocalVariable(name: "I", scope: !2, file: !3, line: 947, type: !4)
> +!2 = distinct !DISubprogram(name: "findInsertLocation", linkageName:
> "_ZL18findInsertLocationPN4llvm17MachineBasicBlockENS_9SlotIndexERNS_13LiveIntervalsE",
> scope: !3, file: !3, line: 937, isLocal: true, isDefinition: true,
> scopeLine: 938, flags: DIFlagPrototyped, isOptimized: true)
> +!3 = !DIFile(filename: "none", directory: ".")
> +!4 = !DICompositeType(tag: DW_TAG_class_type, name:
> "bundle_iterator<llvm::MachineInstr,
> llvm::ilist_iterator<llvm::MachineInstr> >", scope: !5, file: !3, line:
> 163, size: 128, align: 64, elements: !6, templateParams: !6, identifier:
> "_ZTSN4llvm17MachineBasicBlock15bundle_iteratorINS_12MachineInstrENS_14ilist_iteratorIS2_EEEE")
> +!5 = distinct !DICompositeType(tag: DW_TAG_class_type, name:
> "MachineBasicBlock", file: !3, line: 68, size: 1408, align: 64, identifier:
> "_ZTSN4llvm17MachineBasicBlockE")
> +!6 = !{}
> +!7 = !DIExpression()
> +!8 = !DILocation(line: 947, column: 35, scope: !2)
>
>
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