From 0b85459856b3f3efa313436e444849fff9fdda88 Mon Sep 17 00:00:00 2001
From: David Tellenbach <david.tellenbach@arm.com>
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
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@372389 91177308-0d34-0410-b5e6-96231b3b80d8
---
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<bool(Instruction &)>>>
instructionsWithoutDebug();
+ /// Return the size of the basic block ignoring debug instructions
+ filter_iterator<BasicBlock::const_iterator,
+ std::function<bool(const Instruction &)>>::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<BasicBlock::const_iterator,
+ std::function<bool(const Instruction &)>>::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<size_t>(BB1->sizeWithoutDebug()), Exp.size());
+ EXPECT_EQ(static_cast<size_t>(BBConst->sizeWithoutDebug()), Exp.size());
+
delete M;
delete V;
}