[llvm] r355490 - [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 07:11:27 PST 2019
This commit causes an assertion failure when compiling LLVM sources. A
small repro:
$ 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->i
sKnownSentinel()
*** 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
Please revert or fix.
On Wed, Mar 6, 2019 at 11:00 AM Ayonam Ray via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: ayonam
> Date: Wed Mar 6 02:01:02 2019
> New Revision: 355490
>
> URL: http://llvm.org/viewvc/llvm-project?rev=355490&view=rev
> Log:
> [CodeGen] Omit range checks from jump tables when lowering switches with
> unreachable default
>
> During the lowering of a switch that would result in the generation of a
> jump table, a range check is performed before indexing into the jump
> table, for the switch value being outside the jump table range and a
> conditional branch is inserted to jump to the default block. In case the
> default block is unreachable, this conditional jump can be omitted. This
> patch implements omitting this conditional branch for unreachable
> defaults.
>
> Differential Revision: https://reviews.llvm.org/D52002
> Reviewers: Hans Wennborg, Eli Freidman, Roman Lebedev
>
> Added:
> 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=355490&r1=355489&r2=355490&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Wed Mar 6
> 02:01:02 2019
> @@ -2388,24 +2388,31 @@ void SelectionDAGBuilder::visitJumpTable
> JumpTableReg, SwitchOp);
> JT.Reg = JumpTableReg;
>
> - // 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);
> + 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);
> + }
> }
>
> /// Create a LOAD_STACK_GUARD node, and let it carry the target specific
> global
> @@ -9790,10 +9797,13 @@ 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);
> + nullptr, false, OmitRangeCheck);
> JTCases.emplace_back(std::move(JTH), std::move(JT));
>
> JTCluster = CaseCluster::jumpTable(Clusters[First].Low,
> Clusters[Last].High,
> @@ -10599,38 +10609,6 @@ 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=355490&r1=355489&r2=355490&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h Wed Mar 6
> 02:01:02 2019
> @@ -277,11 +277,12 @@ private:
> const Value *SValue;
> MachineBasicBlock *HeaderBB;
> bool Emitted;
> + bool OmitRangeCheck;
>
> JumpTableHeader(APInt F, APInt L, const Value *SV, MachineBasicBlock
> *H,
> - bool E = false)
> + bool E = false, bool ORC = false)
> : First(std::move(F)), Last(std::move(L)), SValue(SV),
> HeaderBB(H),
> - Emitted(E) {}
> + Emitted(E), OmitRangeCheck(ORC) {}
> };
> using JumpTableBlock = std::pair<JumpTableHeader, JumpTable>;
>
>
> Added: 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=355490&view=auto
>
> ==============================================================================
> --- llvm/trunk/test/CodeGen/AArch64/switch-unreachable-default.ll (added)
> +++ llvm/trunk/test/CodeGen/AArch64/switch-unreachable-default.ll Wed Mar
> 6 02:01:02 2019
> @@ -0,0 +1,63 @@
> +; 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=355490&r1=355489&r2=355490&view=diff
>
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/pr38743.ll (original)
> +++ llvm/trunk/test/CodeGen/X86/pr38743.ll Wed Mar 6 02:01:02 2019
> @@ -18,41 +18,43 @@ declare void @llvm.memcpy.p0i8.p0i8.i64(
>
> define void @pr38743() #1 align 2 {
> ; CHECK-LABEL: pr38743:
> -; 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
> +; 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]]
> 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=355490&r1=355489&r2=355490&view=diff
>
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/switch-jump-table.ll (original)
> +++ llvm/trunk/test/CodeGen/X86/switch-jump-table.ll Wed Mar 6 02:01:02
> 2019
> @@ -2,14 +2,12 @@
> ; 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 replaced with the most popular
> case label.
> +; An unreachable default destination is ignored and no compare and branch
> +; is generated for the default values.
>
> 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
> @@ -45,10 +43,12 @@ 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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