[llvm] r355515 - Revert "[CodeGen] Omit range checks from jump tables when lowering switches with unreachable default"
Alexander Kornienko via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 6 07:23:50 PST 2019
Author: alexfh
Date: Wed Mar 6 07:23:50 2019
New Revision: 355515
URL: http://llvm.org/viewvc/llvm-project?rev=355515&view=rev
Log:
Revert "[CodeGen] Omit range checks from jump tables when lowering switches with unreachable default"
This reverts commit 2a0f2c5ef3330846149598220467d9f3c6e8b99c (r355490).
The commit causes an assertion failure when compiling LLVM code:
$ cat repro.cpp
class QQQ {
public:
bool x() const;
bool y() const;
unsigned getSizeInBits() const {
if (y() || x())
return getScalarSizeInBits();
return getScalarSizeInBits() * 2;
}
unsigned getScalarSizeInBits() const;
};
int f(const QQQ &Ty) {
switch (Ty.getSizeInBits()) {
case 1:
case 8:
return 0;
case 16:
return 1;
case 32:
return 2;
case 64:
return 3;
default:
__builtin_unreachable();
}
}
$ clang -O2 -o repro.o repro.cpp
assert.h assertion failed at llvm/include/llvm/ADT/ilist_iterator.h:139 in llvm::ilist_iterator::reference llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::MachineInstr, true, true, void>, true, false>::operator*() const [OptionsT = llvm::ilist_detail::node_options<llvm::MachineInstr, true, true, void>, IsReverse = true, IsConst = false]: !NodePtr->isKnownSentinel()
*** Check failure stack trace: ***
@ 0x558aab4afc10 __assert_fail
@ 0x558aa885479b llvm::ilist_iterator<>::operator*()
@ 0x558aa8854715 llvm::MachineInstrBundleIterator<>::operator*()
@ 0x558aa92c33c3 llvm::X86InstrInfo::optimizeCompareInstr()
@ 0x558aa9a9c251 (anonymous namespace)::PeepholeOptimizer::optimizeCmpInstr()
@ 0x558aa9a9b371 (anonymous namespace)::PeepholeOptimizer::runOnMachineFunction()
@ 0x558aa99a4fc8 llvm::MachineFunctionPass::runOnFunction()
@ 0x558aab019fc4 llvm::FPPassManager::runOnFunction()
@ 0x558aab01a3a5 llvm::FPPassManager::runOnModule()
@ 0x558aab01aa9b (anonymous namespace)::MPPassManager::runOnModule()
@ 0x558aab01a635 llvm::legacy::PassManagerImpl::run()
@ 0x558aab01afe1 llvm::legacy::PassManager::run()
@ 0x558aa5914769 (anonymous namespace)::EmitAssemblyHelper::EmitAssembly()
@ 0x558aa5910f44 clang::EmitBackendOutput()
@ 0x558aa5906135 clang::BackendConsumer::HandleTranslationUnit()
@ 0x558aa6d165ad clang::ParseAST()
@ 0x558aa6a94e22 clang::ASTFrontendAction::ExecuteAction()
@ 0x558aa590255d clang::CodeGenAction::ExecuteAction()
@ 0x558aa6a94840 clang::FrontendAction::Execute()
@ 0x558aa6a38cca clang::CompilerInstance::ExecuteAction()
@ 0x558aa4e2294b clang::ExecuteCompilerInvocation()
@ 0x558aa4df6200 cc1_main()
@ 0x558aa4e1b37f ExecuteCC1Tool()
@ 0x558aa4e1a725 main
@ 0x7ff20d56abbd __libc_start_main
@ 0x558aa4df51c9 _start
Removed:
llvm/trunk/test/CodeGen/AArch64/switch-unreachable-default.ll
Modified:
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
llvm/trunk/test/CodeGen/X86/pr38743.ll
llvm/trunk/test/CodeGen/X86/switch-jump-table.ll
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=355515&r1=355514&r2=355515&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Wed Mar 6 07:23:50 2019
@@ -2388,31 +2388,24 @@ void SelectionDAGBuilder::visitJumpTable
JumpTableReg, SwitchOp);
JT.Reg = JumpTableReg;
- if (!JTH.OmitRangeCheck) {
- // Emit the range check for the jump table, and branch to the default block
- // for the switch statement if the value being switched on exceeds the
- // largest case in the switch.
- SDValue CMP = DAG.getSetCC(
- dl, TLI.getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(),
- Sub.getValueType()),
- Sub, DAG.getConstant(JTH.Last - JTH.First, dl, VT), ISD::SETUGT);
-
- SDValue BrCond = DAG.getNode(ISD::BRCOND, dl,
- MVT::Other, CopyTo, CMP,
- DAG.getBasicBlock(JT.Default));
-
- // Avoid emitting unnecessary branches to the next block.
- if (JT.MBB != NextBlock(SwitchBB))
- BrCond = DAG.getNode(ISD::BR, dl, MVT::Other, BrCond,
- DAG.getBasicBlock(JT.MBB));
-
- DAG.setRoot(BrCond);
- } else {
- SDValue BrCond = DAG.getNode(ISD::BR, dl, MVT::Other, CopyTo,
- DAG.getBasicBlock(JT.MBB));
- DAG.setRoot(BrCond);
- SwitchBB->removeSuccessor(JT.Default, true);
- }
+ // Emit the range check for the jump table, and branch to the default block
+ // for the switch statement if the value being switched on exceeds the largest
+ // case in the switch.
+ SDValue CMP = DAG.getSetCC(
+ dl, TLI.getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(),
+ Sub.getValueType()),
+ Sub, DAG.getConstant(JTH.Last - JTH.First, dl, VT), ISD::SETUGT);
+
+ SDValue BrCond = DAG.getNode(ISD::BRCOND, dl,
+ MVT::Other, CopyTo, CMP,
+ DAG.getBasicBlock(JT.Default));
+
+ // Avoid emitting unnecessary branches to the next block.
+ if (JT.MBB != NextBlock(SwitchBB))
+ BrCond = DAG.getNode(ISD::BR, dl, MVT::Other, BrCond,
+ DAG.getBasicBlock(JT.MBB));
+
+ DAG.setRoot(BrCond);
}
/// Create a LOAD_STACK_GUARD node, and let it carry the target specific global
@@ -9797,13 +9790,10 @@ bool SelectionDAGBuilder::buildJumpTable
->createJumpTableIndex(Table);
// Set up the jump table info.
- bool UnreachableDefault =
- isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg());
- bool OmitRangeCheck = UnreachableDefault;
JumpTable JT(-1U, JTI, JumpTableMBB, nullptr);
JumpTableHeader JTH(Clusters[First].Low->getValue(),
Clusters[Last].High->getValue(), SI->getCondition(),
- nullptr, false, OmitRangeCheck);
+ nullptr, false);
JTCases.emplace_back(std::move(JTH), std::move(JT));
JTCluster = CaseCluster::jumpTable(Clusters[First].Low, Clusters[Last].High,
@@ -10609,6 +10599,38 @@ void SelectionDAGBuilder::visitSwitch(co
// if there are many clusters.
sortAndRangeify(Clusters);
+ if (TM.getOptLevel() != CodeGenOpt::None) {
+ // Replace an unreachable default with the most popular destination.
+ // FIXME: Exploit unreachable default more aggressively.
+ bool UnreachableDefault =
+ isa<UnreachableInst>(SI.getDefaultDest()->getFirstNonPHIOrDbg());
+ if (UnreachableDefault && !Clusters.empty()) {
+ DenseMap<const BasicBlock *, unsigned> Popularity;
+ unsigned MaxPop = 0;
+ const BasicBlock *MaxBB = nullptr;
+ for (auto I : SI.cases()) {
+ const BasicBlock *BB = I.getCaseSuccessor();
+ if (++Popularity[BB] > MaxPop) {
+ MaxPop = Popularity[BB];
+ MaxBB = BB;
+ }
+ }
+ // Set new default.
+ assert(MaxPop > 0 && MaxBB);
+ DefaultMBB = FuncInfo.MBBMap[MaxBB];
+
+ // Remove cases that were pointing to the destination that is now the
+ // default.
+ CaseClusterVector New;
+ New.reserve(Clusters.size());
+ for (CaseCluster &CC : Clusters) {
+ if (CC.MBB != DefaultMBB)
+ New.push_back(CC);
+ }
+ Clusters = std::move(New);
+ }
+ }
+
// The branch probablity of the peeled case.
BranchProbability PeeledCaseProb = BranchProbability::getZero();
MachineBasicBlock *PeeledSwitchMBB =
Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h?rev=355515&r1=355514&r2=355515&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h Wed Mar 6 07:23:50 2019
@@ -277,12 +277,11 @@ private:
const Value *SValue;
MachineBasicBlock *HeaderBB;
bool Emitted;
- bool OmitRangeCheck;
JumpTableHeader(APInt F, APInt L, const Value *SV, MachineBasicBlock *H,
- bool E = false, bool ORC = false)
+ bool E = false)
: First(std::move(F)), Last(std::move(L)), SValue(SV), HeaderBB(H),
- Emitted(E), OmitRangeCheck(ORC) {}
+ Emitted(E) {}
};
using JumpTableBlock = std::pair<JumpTableHeader, JumpTable>;
Removed: llvm/trunk/test/CodeGen/AArch64/switch-unreachable-default.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/switch-unreachable-default.ll?rev=355514&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/switch-unreachable-default.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/switch-unreachable-default.ll (removed)
@@ -1,63 +0,0 @@
-; RUN: llc -O3 -o - %s | FileCheck %s
-
-; Test that the output in the presence of an unreachable default does not have
-; a compare and branch at the top of the switch to handle the default case.
-
-target triple = "aarch64-unknown-linux-gnu"
-
-; Function Attrs: nounwind
-define void @fn(i4) {
- switch i4 %0, label %default [
- i4 0, label %case_0
- i4 1, label %case_1
- i4 2, label %case_2
- i4 3, label %case_3
- i4 4, label %case_4
- i4 5, label %case_5
- ]
-
-; CHECK-LABEL: fn:
-; CHECK-NOT: sub
-; CHECK-NOT: cmp
-; CHECK-NOT: b.hi
-; CHECK: ldrb {{w[0-9]+}}, [{{x[0-9]+}}, {{x[0-9]+}}]
-; CHECK: add {{x[0-9]+}}, {{x[0-9]+}}, {{x[0-9]+}}, lsl #2
-; CHECK: br {{x[0-9]+}}
-
-default:
- unreachable
-
-case_0:
- tail call void @handle_case_00(i4 %0) #2
- br label %return_label
-
-case_1:
- tail call void @handle_case_01(i4 %0) #2
- br label %return_label
-
-case_2:
- tail call void @handle_case_02(i4 %0) #2
- br label %return_label
-
-case_3:
- tail call void @handle_case_03(i4 %0) #2
- br label %return_label
-
-case_4:
- tail call void @handle_case_04(i4 %0) #2
- br label %return_label
-
-case_5:
- tail call void @handle_case_05(i4 %0) #2
- br label %return_label
-
-return_label:
- ret void
-}
-
-declare void @handle_case_00(i4)
-declare void @handle_case_01(i4)
-declare void @handle_case_02(i4)
-declare void @handle_case_03(i4)
-declare void @handle_case_04(i4)
-declare void @handle_case_05(i4)
Modified: llvm/trunk/test/CodeGen/X86/pr38743.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr38743.ll?rev=355515&r1=355514&r2=355515&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/pr38743.ll (original)
+++ llvm/trunk/test/CodeGen/X86/pr38743.ll Wed Mar 6 07:23:50 2019
@@ -18,43 +18,41 @@ declare void @llvm.memcpy.p0i8.p0i8.i64(
define void @pr38743() #1 align 2 {
; CHECK-LABEL: pr38743:
-; CHECK: # %bb.0: # %bb
-; CHECK-NEXT: xorl %eax, %eax
-; CHECK-NEXT: jmpq *.LJTI0_0(,%rax,8)
-; CHECK-NEXT: .[[LABEL1:[A-Z_0-9]+]]: # %bb5
-; CHECK-NEXT: movzwl .str.17+{{.*}}(%rip), %eax
-; CHECK-NEXT: movw %ax, -{{[0-9]+}}(%rsp)
-; CHECK-NEXT: movq .str.17(%rip), %rax
-; CHECK-NEXT: jmp .[[LABEL4:[A-Z_0-9]+]]
-; CHECK-NEXT: .[[LABEL2:[A-Z_0-9]+]]: # %bb2
-; CHECK-NEXT: movq .str.16+{{.*}}(%rip), %rax
-; CHECK-NEXT: movq %rax, -{{[0-9]+}}(%rsp)
-; CHECK-NEXT: movq .str.16(%rip), %rax
-; CHECK-NEXT: jmp .[[LABEL4]]
-; CHECK-NEXT: .[[LABEL3:[A-Z_0-9]+]]: # %bb8
-; CHECK-NEXT: movq .str.18+{{.*}}(%rip), %rax
-; CHECK-NEXT: movq %rax, -{{[0-9]+}}(%rsp)
-; CHECK-NEXT: movq .str.18(%rip), %rax
-; CHECK-NEXT: .[[LABEL4]]: # %bb12
-; CHECK-NEXT: movq %rax, -{{[0-9]+}}(%rsp)
-; CHECK-NEXT: movq -{{[0-9]+}}(%rsp), %rax
-; CHECK-NEXT: movq %rax, (%rax)
-; CHECK-NEXT: movb -{{[0-9]+}}(%rsp), %al
-; CHECK-NEXT: movq -{{[0-9]+}}(%rsp), %rcx
-; CHECK-NEXT: movzwl -{{[0-9]+}}(%rsp), %edx
-; CHECK-NEXT: movl -{{[0-9]+}}(%rsp), %esi
-; CHECK-NEXT: movb -{{[0-9]+}}(%rsp), %dil
-; CHECK-NEXT: movb %al, (%rax)
-; CHECK-NEXT: movq %rcx, {{[0-9]+}}(%rax)
-; CHECK-NEXT: movw %dx, {{[0-9]+}}(%rax)
-; CHECK-NEXT: movl %esi, {{[0-9]+}}(%rax)
-; CHECK-NEXT: movb %dil, {{[0-9]+}}(%rax)
-; CHECK-NEXT: retq
-; CHECK-LABEL: .LJTI0_0:
-; CHECK: .quad .[[LABEL2]]
-; CHECK-NEXT: .quad .[[LABEL1]]
-; CHECK-NEXT: .quad .[[LABEL3]]
-; CHECK-NEXT: .quad .[[LABEL1]]
+; CHECK: # %bb.0: # %bb
+; CHECK-NEXT: cmpl $3, %eax
+; CHECK-NEXT: je .LBB0_4
+; CHECK-NEXT: # %bb.1: # %bb
+; CHECK-NEXT: cmpl $1, %eax
+; CHECK-NEXT: je .LBB0_2
+; CHECK-NEXT: # %bb.3: # %bb5
+; CHECK-NEXT: movzwl .str.17+{{.*}}(%rip), %eax
+; CHECK-NEXT: movw %ax, -{{[0-9]+}}(%rsp)
+; CHECK-NEXT: movq {{.*}}(%rip), %rax
+; CHECK-NEXT: jmp .LBB0_5
+; CHECK-NEXT: .LBB0_4: # %bb8
+; CHECK-NEXT: movq .str.18+{{.*}}(%rip), %rax
+; CHECK-NEXT: movq %rax, -{{[0-9]+}}(%rsp)
+; CHECK-NEXT: movq {{.*}}(%rip), %rax
+; CHECK-NEXT: jmp .LBB0_5
+; CHECK-NEXT: .LBB0_2: # %bb2
+; CHECK-NEXT: movq .str.16+{{.*}}(%rip), %rax
+; CHECK-NEXT: movq %rax, -{{[0-9]+}}(%rsp)
+; CHECK-NEXT: movq {{.*}}(%rip), %rax
+; CHECK-NEXT: .LBB0_5: # %bb12
+; CHECK-NEXT: movq %rax, -{{[0-9]+}}(%rsp)
+; CHECK-NEXT: movq -{{[0-9]+}}(%rsp), %rax
+; CHECK-NEXT: movq %rax, (%rax)
+; CHECK-NEXT: movb -{{[0-9]+}}(%rsp), %al
+; CHECK-NEXT: movq -{{[0-9]+}}(%rsp), %rcx
+; CHECK-NEXT: movzwl -{{[0-9]+}}(%rsp), %edx
+; CHECK-NEXT: movl -{{[0-9]+}}(%rsp), %esi
+; CHECK-NEXT: movb -{{[0-9]+}}(%rsp), %dil
+; CHECK-NEXT: movb %al, (%rax)
+; CHECK-NEXT: movq %rcx, 1(%rax)
+; CHECK-NEXT: movw %dx, 9(%rax)
+; CHECK-NEXT: movl %esi, 11(%rax)
+; CHECK-NEXT: movb %dil, 15(%rax)
+; CHECK-NEXT: retq
bb:
%tmp = alloca %0, align 16
%tmp1 = bitcast %0* %tmp to i8*
Modified: llvm/trunk/test/CodeGen/X86/switch-jump-table.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/switch-jump-table.ll?rev=355515&r1=355514&r2=355515&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/switch-jump-table.ll (original)
+++ llvm/trunk/test/CodeGen/X86/switch-jump-table.ll Wed Mar 6 07:23:50 2019
@@ -2,12 +2,14 @@
; RUN: llc -mtriple=i686-pc-gnu-linux -print-machineinstrs=expand-isel-pseudos %s -o /dev/null 2>&1 | FileCheck %s -check-prefix=CHECK-JT-PROB
-; An unreachable default destination is ignored and no compare and branch
-; is generated for the default values.
+; An unreachable default destination is replaced with the most popular case label.
define void @foo(i32 %x, i32* %to) {
; CHECK-LABEL: foo:
; CHECK: movl 4(%esp), [[REG:%e[a-z]{2}]]
+; CHECK: cmpl $3, [[REG]]
+; CHECK: ja .LBB0_6
+; CHECK-NEXT: # %bb.1:
; CHECK-NEXT: jmpl *.LJTI0_0(,[[REG]],4)
; CHECK: movl $4
; CHECK: retl
@@ -43,12 +45,10 @@ default:
; The jump table has four entries.
; CHECK-LABEL: .LJTI0_0:
-; CHECK-NEXT: .long .LBB0_1
; CHECK-NEXT: .long .LBB0_2
; CHECK-NEXT: .long .LBB0_3
; CHECK-NEXT: .long .LBB0_4
; CHECK-NEXT: .long .LBB0_5
-; CHECK-NEXT: .long .LBB0_5
}
; Check if branch probabilities are correctly assigned to the jump table.
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