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[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

llvm-svn: 257795
This commit is contained in:
Keno Fischer 2016-01-14 20:06:34 +00:00
parent 60b201b662
commit d5354fdddb
2 changed files with 42 additions and 2 deletions
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7
llvm/lib/Transforms/Scalar/SROA.cpp
View File

@ -4024,12 +4024,12 @@ bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &AS) {
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, AllocaSlices &AS) {
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.

37
llvm/test/Transforms/SROA/dbg-single-piece.ll Normal file
View File

@ -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)