diff --git a/include/llvm/Target/TargetLowering.h b/include/llvm/Target/TargetLowering.h
index 93bdeaaff0e..66eb4179ff6 100644
--- a/include/llvm/Target/TargetLowering.h
+++ b/include/llvm/Target/TargetLowering.h
@@ -1022,12 +1022,15 @@ public:
return UseUnderscoreLongJmp;
}
- /// Return integer threshold on number of blocks to use jump tables rather
- /// than if sequence.
- int getMinimumJumpTableEntries() const {
+ /// Return lower limit for number of blocks in a jump table.
+ unsigned getMinimumJumpTableEntries() const {
return MinimumJumpTableEntries;
}
+ /// Return upper limit for number of entries in a jump table.
+ /// Zero if no limit.
+ unsigned getMaximumJumpTableSize() const;
+
/// If a physical register, this specifies the register that
/// llvm.savestack/llvm.restorestack should save and restore.
unsigned getStackPointerRegisterToSaveRestore() const {
@@ -1353,12 +1356,15 @@ protected:
UseUnderscoreLongJmp = Val;
}
- /// Indicate the number of blocks to generate jump tables rather than if
- /// sequence.
- void setMinimumJumpTableEntries(int Val) {
+ /// Indicate the minimum number of blocks to generate jump tables.
+ void setMinimumJumpTableEntries(unsigned Val) {
MinimumJumpTableEntries = Val;
}
+ /// Indicate the maximum number of entries in jump tables.
+ /// Set to zero to generate unlimited jump tables.
+ void setMaximumJumpTableSize(unsigned);
+
/// If set to a physical register, this specifies the register that
/// llvm.savestack/llvm.restorestack should save and restore.
void setStackPointerRegisterToSaveRestore(unsigned R) {
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index a0db9ae34f8..5a4d49d9368 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -8454,12 +8454,19 @@ void SelectionDAGBuilder::findJumpTables(CaseClusterVector &Clusters,
if (!areJTsAllowed(TLI, SI))
return;
+ const bool OptForSize = DefaultMBB->getParent()->getFunction()->optForSize();
+
const int64_t N = Clusters.size();
- const unsigned MinJumpTableSize = TLI.getMinimumJumpTableEntries();
+ const unsigned MinJumpTableEntries = TLI.getMinimumJumpTableEntries();
+ const unsigned MaxJumpTableSize =
+ OptForSize ? UINT_MAX : TLI.getMaximumJumpTableSize() ?
+ TLI.getMaximumJumpTableSize() : UINT_MAX;
+
+ if (N < 2 || N < MinJumpTableEntries)
+ return;
// TotalCases[i]: Total nbr of cases in Clusters[0..i].
SmallVector<unsigned, 8> TotalCases(N);
-
for (unsigned i = 0; i < N; ++i) {
const APInt &Hi = Clusters[i].High->getValue();
const APInt &Lo = Clusters[i].Low->getValue();
@@ -8468,12 +8475,16 @@ void SelectionDAGBuilder::findJumpTables(CaseClusterVector &Clusters,
TotalCases[i] += TotalCases[i - 1];
}
- unsigned MinDensity = JumpTableDensity;
- if (DefaultMBB->getParent()->getFunction()->optForSize())
- MinDensity = OptsizeJumpTableDensity;
- if (N >= MinJumpTableSize
- && isDense(Clusters, TotalCases, 0, N - 1, MinDensity)) {
- // Cheap case: the whole range might be suitable for jump table.
+ const unsigned MinDensity =
+ OptForSize ? OptsizeJumpTableDensity : JumpTableDensity;
+
+ // Cheap case: the whole range may be suitable for jump table.
+ unsigned JumpTableSize = (Clusters[N - 1].High->getValue() -
+ Clusters[0].Low->getValue())
+ .getLimitedValue(UINT_MAX - 1) + 1;
+ if (JumpTableSize <= MaxJumpTableSize &&
+ isDense(Clusters, TotalCases, 0, N - 1, MinDensity)) {
+
CaseCluster JTCluster;
if (buildJumpTable(Clusters, 0, N - 1, SI, DefaultMBB, JTCluster)) {
Clusters[0] = JTCluster;
@@ -8503,7 +8514,6 @@ void SelectionDAGBuilder::findJumpTables(CaseClusterVector &Clusters,
// Base case: There is only one way to partition Clusters[N-1].
MinPartitions[N - 1] = 1;
LastElement[N - 1] = N - 1;
- assert(MinJumpTableSize > 1);
NumTables[N - 1] = 0;
// Note: loop indexes are signed to avoid underflow.
@@ -8517,9 +8527,13 @@ void SelectionDAGBuilder::findJumpTables(CaseClusterVector &Clusters,
// Search for a solution that results in fewer partitions.
for (int64_t j = N - 1; j > i; j--) {
// Try building a partition from Clusters[i..j].
- if (isDense(Clusters, TotalCases, i, j, MinDensity)) {
+ JumpTableSize = (Clusters[j].High->getValue() -
+ Clusters[i].Low->getValue())
+ .getLimitedValue(UINT_MAX - 1) + 1;
+ if (JumpTableSize <= MaxJumpTableSize &&
+ isDense(Clusters, TotalCases, i, j, MinDensity)) {
unsigned NumPartitions = 1 + (j == N - 1 ? 0 : MinPartitions[j + 1]);
- bool IsTable = j - i + 1 >= MinJumpTableSize;
+ bool IsTable = j - i + 1 >= MinJumpTableEntries;
unsigned Tables = IsTable + (j == N - 1 ? 0 : NumTables[j + 1]);
// If this j leads to fewer partitions, or same number of partitions
@@ -8543,7 +8557,7 @@ void SelectionDAGBuilder::findJumpTables(CaseClusterVector &Clusters,
unsigned NumClusters = Last - First + 1;
CaseCluster JTCluster;
- if (NumClusters >= MinJumpTableSize &&
+ if (NumClusters >= MinJumpTableEntries &&
buildJumpTable(Clusters, First, Last, SI, DefaultMBB, JTCluster)) {
Clusters[DstIndex++] = JTCluster;
} else {
diff --git a/lib/CodeGen/TargetLoweringBase.cpp b/lib/CodeGen/TargetLoweringBase.cpp
index 4c11f2131f2..be66f7e9e0e 100644
--- a/lib/CodeGen/TargetLoweringBase.cpp
+++ b/lib/CodeGen/TargetLoweringBase.cpp
@@ -44,6 +44,10 @@ static cl::opt<bool> JumpIsExpensiveOverride(
cl::desc("Do not create extra branches to split comparison logic."),
cl::Hidden);
+static cl::opt<unsigned> MaximumJumpTableSize
+ ("max-jump-table", cl::init(0), cl::Hidden,
+ cl::desc("Set maximum number of jump table entries; zero for no limit."));
+
// Although this default value is arbitrary, it is not random. It is assumed
// that a condition that evaluates the same way by a higher percentage than this
// is best represented as control flow. Therefore, the default value N should be
@@ -1831,3 +1835,11 @@ Value *TargetLoweringBase::getSDagStackGuard(const Module &M) const {
Value *TargetLoweringBase::getSSPStackGuardCheck(const Module &M) const {
return nullptr;
}
+
+unsigned TargetLoweringBase::getMaximumJumpTableSize() const {
+ return MaximumJumpTableSize;
+}
+
+void TargetLoweringBase::setMaximumJumpTableSize(unsigned Val) {
+ MaximumJumpTableSize = Val;
+}
diff --git a/lib/Target/AArch64/AArch64ISelLowering.cpp b/lib/Target/AArch64/AArch64ISelLowering.cpp
index a611549c912..7647ea2fd65 100644
--- a/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -513,6 +513,12 @@ AArch64TargetLowering::AArch64TargetLowering(const TargetMachine &TM,
setPrefFunctionAlignment(STI.getPrefFunctionAlignment());
setPrefLoopAlignment(STI.getPrefLoopAlignment());
+ // Only change the limit for entries in a jump table if specified by
+ // the subtarget, but not at the command line.
+ unsigned MaxJT = STI.getMaximumJumpTableSize();
+ if (MaxJT && getMaximumJumpTableSize() == 0)
+ setMaximumJumpTableSize(MaxJT);
+
setHasExtractBitsInsn(true);
setOperationAction(ISD::INTRINSIC_WO_CHAIN, MVT::Other, Custom);
diff --git a/lib/Target/AArch64/AArch64Subtarget.cpp b/lib/Target/AArch64/AArch64Subtarget.cpp
index d257e81a952..2d346cb512a 100644
--- a/lib/Target/AArch64/AArch64Subtarget.cpp
+++ b/lib/Target/AArch64/AArch64Subtarget.cpp
@@ -65,6 +65,7 @@ void AArch64Subtarget::initializeProperties() {
case ExynosM1:
PrefFunctionAlignment = 4;
PrefLoopAlignment = 3;
+ MaxJumpTableSize = 12;
break;
case Kryo:
MaxInterleaveFactor = 4;
diff --git a/lib/Target/AArch64/AArch64Subtarget.h b/lib/Target/AArch64/AArch64Subtarget.h
index 0ab823b4e6b..bda29196388 100644
--- a/lib/Target/AArch64/AArch64Subtarget.h
+++ b/lib/Target/AArch64/AArch64Subtarget.h
@@ -90,6 +90,7 @@ protected:
unsigned MaxPrefetchIterationsAhead = UINT_MAX;
unsigned PrefFunctionAlignment = 0;
unsigned PrefLoopAlignment = 0;
+ unsigned MaxJumpTableSize = 0;
// ReserveX18 - X18 is not available as a general purpose register.
bool ReserveX18;
@@ -203,6 +204,8 @@ public:
unsigned getPrefFunctionAlignment() const { return PrefFunctionAlignment; }
unsigned getPrefLoopAlignment() const { return PrefLoopAlignment; }
+ unsigned getMaximumJumpTableSize() const { return MaxJumpTableSize; }
+
/// CPU has TBI (top byte of addresses is ignored during HW address
/// translation) and OS enables it.
bool supportsAddressTopByteIgnored() const;
diff --git a/test/CodeGen/AArch64/max-jump-table.ll b/test/CodeGen/AArch64/max-jump-table.ll
new file mode 100644
index 00000000000..9b46ff64904
--- /dev/null
+++ b/test/CodeGen/AArch64/max-jump-table.ll
@@ -0,0 +1,94 @@
+; RUN: llc %s -O2 -print-machineinstrs -march=aarch64 -jump-table-density=40 -o - 2>%t; FileCheck %s --check-prefixes=CHECK,CHECK0 <%t
+; RUN: llc %s -O2 -print-machineinstrs -march=aarch64 -jump-table-density=40 -max-jump-table=4 -o - 2>%t; FileCheck %s --check-prefixes=CHECK,CHECK4 <%t
+; RUN: llc %s -O2 -print-machineinstrs -march=aarch64 -jump-table-density=40 -max-jump-table=8 -o - 2>%t; FileCheck %s --check-prefixes=CHECK,CHECK8 <%t
+; RUN: llc %s -O2 -print-machineinstrs -march=aarch64 -jump-table-density=40 -mcpu=exynos-m1 -o - 2>%t; FileCheck %s --check-prefixes=CHECK,CHECKM1 <%t
+
+declare void @ext(i32)
+
+define i32 @jt1(i32 %a, i32 %b) {
+entry:
+ switch i32 %a, label %return [
+ i32 1, label %bb1
+ i32 2, label %bb2
+ i32 3, label %bb3
+ i32 4, label %bb4
+ i32 5, label %bb5
+ i32 6, label %bb6
+ i32 7, label %bb7
+ i32 8, label %bb8
+ i32 9, label %bb9
+ i32 10, label %bb10
+ i32 11, label %bb11
+ i32 12, label %bb12
+ i32 13, label %bb13
+ i32 14, label %bb14
+ i32 15, label %bb15
+ i32 16, label %bb16
+ i32 17, label %bb17
+ ]
+; CHECK-LABEL: function jt1:
+; CHECK: Jump Tables:
+; CHECK0-NEXT: jt#0:
+; CHECK0-NOT: jt#1:
+; CHECK4-NEXT: jt#0:
+; CHECK4-SAME: jt#1:
+; CHECK4-SAME: jt#2:
+; CHECK4-SAME: jt#3:
+; CHECK4-NOT: jt#4:
+; CHECK8-NEXT: jt#0:
+; CHECK8-SAME: jt#1:
+; CHECK8-SAME: jt#2: BB#14 BB#15 BB#16 BB#17{{$}}
+; CHECK8-NOT: jt#3:
+; CHECKM1-NEXT: jt#0:
+; CHECKM1-SAME: jt#1: BB#13 BB#14 BB#15 BB#16 BB#17{{$}}
+; CHECKM1-NOT: jt#2:
+; CHEC-NEXT: Function Live Ins:
+
+bb1: tail call void @ext(i32 0) br label %return
+bb2: tail call void @ext(i32 2) br label %return
+bb3: tail call void @ext(i32 4) br label %return
+bb4: tail call void @ext(i32 6) br label %return
+bb5: tail call void @ext(i32 8) br label %return
+bb6: tail call void @ext(i32 10) br label %return
+bb7: tail call void @ext(i32 12) br label %return
+bb8: tail call void @ext(i32 14) br label %return
+bb9: tail call void @ext(i32 16) br label %return
+bb10: tail call void @ext(i32 18) br label %return
+bb11: tail call void @ext(i32 20) br label %return
+bb12: tail call void @ext(i32 22) br label %return
+bb13: tail call void @ext(i32 24) br label %return
+bb14: tail call void @ext(i32 26) br label %return
+bb15: tail call void @ext(i32 28) br label %return
+bb16: tail call void @ext(i32 30) br label %return
+bb17: tail call void @ext(i32 32) br label %return
+
+return: ret i32 %b
+}
+
+define void @jt2(i32 %x) {
+entry:
+ switch i32 %x, label %return [
+ i32 1, label %bb1
+ i32 2, label %bb2
+ i32 3, label %bb3
+ i32 4, label %bb4
+
+ i32 14, label %bb5
+ i32 15, label %bb6
+ ]
+; CHECK-LABEL: function jt2:
+; CHECK: Jump Tables:
+; CHECK0-NEXT: jt#0: BB#1 BB#2 BB#3 BB#4 BB#7 BB#7 BB#7 BB#7 BB#7 BB#7 BB#7 BB#7 BB#7 BB#5 BB#6{{$}}
+; CHECK4-NEXT: jt#0: BB#1 BB#2 BB#3 BB#4{{$}}
+; CHECK8-NEXT: jt#0: BB#1 BB#2 BB#3 BB#4{{$}}
+; CHECKM1-NEXT: jt#0: BB#1 BB#2 BB#3 BB#4{{$}}
+; CHEC-NEXT: Function Live Ins:
+
+bb1: tail call void @ext(i32 1) br label %return
+bb2: tail call void @ext(i32 2) br label %return
+bb3: tail call void @ext(i32 3) br label %return
+bb4: tail call void @ext(i32 4) br label %return
+bb5: tail call void @ext(i32 5) br label %return
+bb6: tail call void @ext(i32 6) br label %return
+return: ret void
+}