From 9337b9eb4a60adbb09a8481aac625fa5531a82d5 Mon Sep 17 00:00:00 2001 From: David Tellenbach Date: Fri, 20 Sep 2019 13:22:59 +0000 Subject: [PATCH] [FastISel] Fix insertion of unconditional branches during FastISel The insertion of an unconditional branch during FastISel can differ depending on building with or without debug information. This happens because FastISel::fastEmitBranch emits an unconditional branch depending on the size of the current basic block without distinguishing between debug and non-debug instructions. This patch fixes this issue by ignoring debug instructions when getting the size of the basic block. Reviewers: aprantl Reviewed By: aprantl Subscribers: ormris, aprantl, hiraditya, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D67703 llvm-svn: 372389 --- include/llvm/IR/BasicBlock.h | 5 +++ lib/CodeGen/SelectionDAG/FastISel.cpp | 8 ++-- lib/IR/BasicBlock.cpp | 7 +++ .../AArch64/fast-isel-branch-uncond-debug.ll | 44 +++++++++++++++++++ unittests/IR/BasicBlockTest.cpp | 3 ++ 5 files changed, 63 insertions(+), 4 deletions(-) create mode 100644 test/CodeGen/AArch64/fast-isel-branch-uncond-debug.ll diff --git a/include/llvm/IR/BasicBlock.h b/include/llvm/IR/BasicBlock.h index 69555af50e1..d594145f863 100644 --- a/include/llvm/IR/BasicBlock.h +++ b/include/llvm/IR/BasicBlock.h @@ -192,6 +192,11 @@ public: std::function>> instructionsWithoutDebug(); + /// Return the size of the basic block ignoring debug instructions + filter_iterator>::difference_type + sizeWithoutDebug() const; + /// Unlink 'this' from the containing function, but do not delete it. void removeFromParent(); diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp index f8352ca2fe6..8904283ff8d 100644 --- a/lib/CodeGen/SelectionDAG/FastISel.cpp +++ b/lib/CodeGen/SelectionDAG/FastISel.cpp @@ -1677,11 +1677,11 @@ bool FastISel::selectInstruction(const Instruction *I) { /// (fall-through) successor, and update the CFG. void FastISel::fastEmitBranch(MachineBasicBlock *MSucc, const DebugLoc &DbgLoc) { - if (FuncInfo.MBB->getBasicBlock()->size() > 1 && + if (FuncInfo.MBB->getBasicBlock()->sizeWithoutDebug() > 1 && FuncInfo.MBB->isLayoutSuccessor(MSucc)) { - // For more accurate line information if this is the only instruction - // in the block then emit it, otherwise we have the unconditional - // fall-through case, which needs no instructions. + // For more accurate line information if this is the only non-debug + // instruction in the block then emit it, otherwise we have the + // unconditional fall-through case, which needs no instructions. } else { // The unconditional branch case. TII.insertBranch(*FuncInfo.MBB, MSucc, nullptr, diff --git a/lib/IR/BasicBlock.cpp b/lib/IR/BasicBlock.cpp index 34410712645..bdee6990f93 100644 --- a/lib/IR/BasicBlock.cpp +++ b/lib/IR/BasicBlock.cpp @@ -107,6 +107,13 @@ BasicBlock::instructionsWithoutDebug() { return make_filter_range(*this, Fn); } +filter_iterator>::difference_type +BasicBlock::sizeWithoutDebug() const { + return std::distance(instructionsWithoutDebug().begin(), + instructionsWithoutDebug().end()); +} + void BasicBlock::removeFromParent() { getParent()->getBasicBlockList().remove(getIterator()); } diff --git a/test/CodeGen/AArch64/fast-isel-branch-uncond-debug.ll b/test/CodeGen/AArch64/fast-isel-branch-uncond-debug.ll new file mode 100644 index 00000000000..902ec7a9c09 --- /dev/null +++ b/test/CodeGen/AArch64/fast-isel-branch-uncond-debug.ll @@ -0,0 +1,44 @@ +; RUN: llc -mtriple=aarch64-arm-none-eabi -O1 -opt-bisect-limit=2 -o - %s 2> /dev/null | FileCheck %s + +define dso_local i32 @a() #0 !dbg !7 { +entry: +; CHECK: b .LBB0_1 +; CHECK: .LBB0_1: + call void @llvm.dbg.value(metadata i32 0, metadata !12, metadata !DIExpression()), !dbg !13 + br label %for.cond, !dbg !14 + +; CHECK: b .LBB0_1 +; CHECK: .Lfunc_end0: +for.cond: + br label %for.cond, !dbg !15, !llvm.loop !18 +} +declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #1 + +declare void @llvm.dbg.value(metadata, metadata, metadata) #2 + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!3, !4, !5} +!llvm.ident = !{!6} + +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None) +!1 = !DIFile(filename: "fast-isel-branch-uncond-debug.ll", directory: "/tmp") +!2 = !{} +!3 = !{i32 2, !"Dwarf Version", i32 4} +!4 = !{i32 2, !"Debug Info Version", i32 3} +!5 = !{i32 1, !"wchar_size", i32 4} +!6 = !{!""} +!7 = distinct !DISubprogram(name: "a", scope: !1, file: !1, line: 1, type: !8, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11) +!8 = !DISubroutineType(types: !9) +!9 = !{!10} +!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) +!11 = !{!12} +!12 = !DILocalVariable(name: "b", scope: !7, file: !1, line: 2, type: !10) +!13 = !DILocation(line: 0, scope: !7) +!14 = !DILocation(line: 3, column: 3, scope: !7) +!15 = !DILocation(line: 3, column: 3, scope: !16) +!16 = distinct !DILexicalBlock(scope: !17, file: !1, line: 3, column: 3) +!17 = distinct !DILexicalBlock(scope: !7, file: !1, line: 3, column: 3) +!18 = distinct !{!18, !19, !20} +!19 = !DILocation(line: 3, column: 3, scope: !17) +!20 = !DILocation(line: 4, column: 5, scope: !17) + \ No newline at end of file diff --git a/unittests/IR/BasicBlockTest.cpp b/unittests/IR/BasicBlockTest.cpp index 95bc242ec30..ad446ee6eba 100644 --- a/unittests/IR/BasicBlockTest.cpp +++ b/unittests/IR/BasicBlockTest.cpp @@ -122,6 +122,9 @@ TEST(BasicBlockTest, TestInstructionsWithoutDebug) { CHECK_ITERATORS(BB1->instructionsWithoutDebug(), Exp); CHECK_ITERATORS(BBConst->instructionsWithoutDebug(), Exp); + EXPECT_EQ(static_cast(BB1->sizeWithoutDebug()), Exp.size()); + EXPECT_EQ(static_cast(BBConst->sizeWithoutDebug()), Exp.size()); + delete M; delete V; }