gulfem updated this revision to Diff 320025.
gulfem added a comment.
1. Simplified test cases and increased readibility of the tables
2. Added x86_64 and aarch64 check and tiny or small code modes check to ensure
32 offsets
3. Modified single value test case
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D94355/new/
https://reviews.llvm.org/D94355
Files:
clang/test/CodeGen/switch-to-lookup-table.c
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/test/Transforms/SimplifyCFG/X86/switch_to_relative_lookup_table.ll
Index: llvm/test/Transforms/SimplifyCFG/X86/switch_to_relative_lookup_table.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/SimplifyCFG/X86/switch_to_relative_lookup_table.ll
@@ -0,0 +1,211 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -simplifycfg -switch-to-lookup=true -keep-loops=false -S -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+; RUN: opt < %s -passes='simplify-cfg<switch-to-lookup;no-keep-loops>' -S -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@.str = private unnamed_addr constant [5 x i8] c"zero\00", align 1
+@.str.1 = private unnamed_addr constant [4 x i8] c"one\00", align 1
+@.str.2 = private unnamed_addr constant [4 x i8] c"two\00", align 1
+@.str.3 = private unnamed_addr constant [8 x i8] c"default\00", align 1
+@.str.4 = private unnamed_addr constant [6 x i8] c"three\00", align 1
+@.str.5 = private unnamed_addr constant [5 x i8] c"str1\00", align 1
+@.str.6 = private unnamed_addr constant [5 x i8] c"str2\00", align 1
+@.str.7 = private unnamed_addr constant [12 x i8] c"singlevalue\00", align 1
+
+; Relative string table lookup
+; CHECK: @switch.reltable.string_table = private unnamed_addr constant [3 x i32]
+; CHECK-SAME: [
+; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str to i64), i64 ptrtoint ([3 x i32]* @switch.reltable.string_table to i64)) to i32),
+; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.1 to i64), i64 ptrtoint ([3 x i32]* @switch.reltable.string_table to i64)) to i32),
+; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.2 to i64), i64 ptrtoint ([3 x i32]* @switch.reltable.string_table to i64)) to i32)
+; CHECK-SAME: ], align 4
+
+; Relative string table lookup that holes are filled with relative offset to default values
+; CHECK: @switch.reltable.string_table_holes = private unnamed_addr constant [4 x i32]
+; CHECK-SAME: [
+; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str to i64), i64 ptrtoint ([4 x i32]* @switch.reltable.string_table_holes to i64)) to i32),
+; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint ([8 x i8]* @.str.3 to i64), i64 ptrtoint ([4 x i32]* @switch.reltable.string_table_holes to i64)) to i32),
+; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.2 to i64), i64 ptrtoint ([4 x i32]* @switch.reltable.string_table_holes to i64)) to i32),
+; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint ([6 x i8]* @.str.4 to i64), i64 ptrtoint ([4 x i32]* @switch.reltable.string_table_holes to i64)) to i32)
+; CHECK-SAME: ], align 4
+
+; Integer pointer table lookup
+; CHECK: @switch.table.no_dso_local = private unnamed_addr constant [7 x i32*] [i32* @a, i32* @b, i32* @c, i32* @d, i32* @e, i32* @f, i32* @g], align 8
+
+; Single value check
+; CHECK: @switch.reltable.single_value = private unnamed_addr constant [3 x i32]
+; CHECK-SAME: [
+; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str to i64), i64 ptrtoint ([3 x i32]* @switch.reltable.single_value to i64)) to i32),
+; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.1 to i64), i64 ptrtoint ([3 x i32]* @switch.reltable.single_value to i64)) to i32),
+; CHECK-SAME: i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.2 to i64), i64 ptrtoint ([3 x i32]* @switch.reltable.single_value to i64)) to i32)
+; CHECK-SAME: ], align 4
+
+; Switch used to return a string.
+; Relative lookup table should be generated.
+define i8* @string_table(i32 %cond) {
+ ; CHECK-LABEL: @string_table(
+ ; CHECK-NEXT: entry:
+ ; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 [[COND:%.*]], 3
+ ; CHECK-NEXT: br i1 [[TMP0]], label [[SWITCH_LOOKUP:%.*]], label [[RETURN:%.*]]
+ ; CHECK: switch.lookup:
+ ; CHECK-NEXT: [[SWITCH_RELTABLE_SHIFT:%.*]] = lshr i32 %cond, 2
+ ; CHECK-NEXT: [[SWITCH_RELTABLE_INTRINSIC:%.*]] = call i8* @llvm.load.relative.i32(i8* bitcast ([3 x i32]* @switch.reltable.string_table to i8*), i32 [[SWITCH_RELTABLE_SHIFT]])
+ ; CHECK-NEXT: ret i8* [[SWITCH_RELTABLE_INTRINSIC]]
+ ; CHECK: return:
+ ; CHECK-NEXT: ret i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.3, i64 0, i64 0)
+entry:
+ switch i32 %cond, label %sw.default [
+ i32 0, label %return
+ i32 1, label %sw.bb1
+ i32 2, label %sw.bb2
+ ]
+
+sw.bb1: ; preds = %entry
+ br label %return
+
+sw.bb2: ; preds = %entry
+ br label %return
+
+sw.default: ; preds = %entry
+ br label %return
+
+return: ; preds = %entry, %sw.default, %sw.bb2, %sw.bb1
+ %retval.0 = phi i8* [ getelementptr inbounds ([8 x i8], [8 x i8]* @.str.3, i64 0, i64 0), %sw.default ], [ getelementptr inbounds ([4 x i8], [4 x i8]* @.str.2, i64 0, i64 0), %sw.bb2 ], [ getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0), %sw.bb1 ], [ getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), %entry ]
+ ret i8* %retval.0
+}
+
+; Fill the holes with offset of the default value in the relative lookup table.
+define i8* @string_table_holes(i32 %cond) {
+; CHECK-LABEL: @string_table_holes(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 [[COND:%.*]], 4
+; CHECK-NEXT: br i1 [[TMP0]], label [[SWITCH_LOOKUP:%.*]], label [[RETURN:%.*]]
+; CHECK: switch.lookup:
+; CHECK-NEXT: [[SWITCH_RELTABLE_SHIFT:%.*]] = lshr i32 [[COND:%.*]], 2
+; CHECK-NEXT: [[SWITCH_RELTABLE_INTRINSIC:%.*]] = call i8* @llvm.load.relative.i32(i8* bitcast ([4 x i32]* @switch.reltable.string_table_holes to i8*), i32 [[SWITCH_RELTABLE_SHIFT]])
+; CHECK-NEXT: ret i8* [[SWITCH_RELTABLE_INTRINSIC]]
+; CHECK: return:
+; CHECK-NEXT: ret i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.3, i64 0, i64 0)
+;
+entry:
+ switch i32 %cond, label %sw.default [
+ i32 0, label %return
+ i32 2, label %sw.bb1
+ i32 3, label %sw.bb2
+ ]
+
+sw.bb1: ; preds = %entry
+ br label %return
+
+sw.bb2: ; preds = %entry
+ br label %return
+
+sw.default: ; preds = %entry
+ br label %return
+
+return: ; preds = %entry, %sw.default, %sw.bb2, %sw.bb1
+ %retval.0 = phi i8* [ getelementptr inbounds ([8 x i8], [8 x i8]* @.str.3, i64 0, i64 0), %sw.default ], [ getelementptr inbounds ([6 x i8], [6 x i8]* @.str.4, i64 0, i64 0), %sw.bb2 ], [ getelementptr inbounds ([4 x i8], [4 x i8]* @.str.2, i64 0, i64 0), %sw.bb1 ], [ getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), %entry ]
+ ret i8* %retval.0
+}
+
+@a = external global i32, align 4
+@b = external global i32, align 4
+@c = external global i32, align 4
+@d = external global i32, align 4
+@e = external global i32, align 4
+@f = external global i32, align 4
+@g = external global i32, align 4
+@h = external global i32, align 4
+
+; If pointers are not dso_local, relative lookup table should not be generated.
+define i32* @no_dso_local(i32 %cond) {
+; CHECK-LABEL: @no_dso_local(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 [[COND:%.*]], 7
+; CHECK-NEXT: br i1 [[TMP0]], label [[SWITCH_LOOKUP:%.*]], label [[RETURN:%.*]]
+; CHECK: switch.lookup:
+; CHECK-NEXT: [[SWITCH_GEP:%.*]] = getelementptr inbounds [7 x i32*], [7 x i32*]* @switch.table.no_dso_local, i32 0, i32 [[COND:%.*]]
+; CHECK-NEXT: [[SWITCH_LOAD:%.*]] = load i32*, i32** [[SWITCH_GEP]], align 8
+; CHECK-NEXT: ret i32* [[SWITCH_LOAD]]
+; CHECK: return:
+; CHECK-NEXT: ret i32* @h
+;
+entry:
+ switch i32 %cond, label %sw.default [
+ i32 0, label %return
+ i32 1, label %sw.bb1
+ i32 2, label %sw.bb2
+ i32 3, label %sw.bb3
+ i32 4, label %sw.bb4
+ i32 5, label %sw.bb5
+ i32 6, label %sw.bb6
+ ]
+
+sw.bb1: ; preds = %entry
+ br label %return
+
+sw.bb2: ; preds = %entry
+ br label %return
+
+sw.bb3: ; preds = %entry
+ br label %return
+
+sw.bb4: ; preds = %entry
+ br label %return
+
+sw.bb5: ; preds = %entry
+ br label %return
+
+sw.bb6: ; preds = %entry
+ br label %return
+
+sw.default: ; preds = %entry
+ br label %return
+
+return: ; preds = %entry, %sw.default, %sw.bb6, %sw.bb5, %sw.bb4, %sw.bb3, %sw.bb2, %sw.bb1
+ %retval.0 = phi i32* [ @h, %sw.default ], [ @g, %sw.bb6 ], [ @f, %sw.bb5 ], [ @e, %sw.bb4 ], [ @d, %sw.bb3 ], [ @c, %sw.bb2 ], [ @b, %sw.bb1 ], [ @a, %entry ]
+ ret i32* %retval.0
+}
+
+; Single value check
+; If there is a lookup table, where each element contains the same value,
+; a relative lookup should not be generated
+define void @single_value(i32 %cond) {
+; CHECK-LABEL: @single_value(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 [[COND:%.*]], 3
+; CHECK-NEXT: br i1 [[TMP0]], label [[SWITCH_LOOKUP:%.*]], label [[RETURN:%.*]]
+; CHECK: switch.lookup:
+; CHECK-NEXT: [[SWITCH_RELTABLE_SHIFT:%.*]] = lshr i32 [[COND:%.*]], 2
+; CHECK-NEXT: [[SWITCH_RELTABLE_INTRINSIC:%.*]] = call i8* @llvm.load.relative.i32(i8* bitcast ([3 x i32]* @switch.reltable.single_value to i8*), i32 [[SWITCH_RELTABLE_SHIFT]])
+; CHECK: sw.epilog:
+; CHECK-NEXT: [[STR1:%.*]] = phi i8* [ getelementptr inbounds ([5 x i8], [5 x i8]* @.str.5, i64 0, i64 0), %entry ], [ getelementptr inbounds ([12 x i8], [12 x i8]* @.str.7, i64 0, i64 0), %switch.lookup ]
+; CHECK-NEXT: [[STR2:%.*]] = phi i8* [ getelementptr inbounds ([5 x i8], [5 x i8]* @.str.6, i64 0, i64 0), %entry ], [ %switch.reltable.intrinsic, %switch.lookup ]
+; CHECK-NEXT: ret void
+
+entry:
+ switch i32 %cond, label %sw.epilog [
+ i32 0, label %sw.bb
+ i32 1, label %sw.bb1
+ i32 2, label %sw.bb2
+ ]
+
+sw.bb: ; preds = %entry
+ br label %sw.epilog
+
+sw.bb1: ; preds = %entry
+ br label %sw.epilog
+
+sw.bb2: ; preds = %entry
+ br label %sw.epilog
+
+sw.epilog: ; preds = %entry, %sw.bb2, %sw.bb1, %sw.bb
+ %str1.0 = phi i8* [ getelementptr inbounds ([5 x i8], [5 x i8]* @.str.5, i64 0, i64 0), %entry ], [ getelementptr inbounds ([12 x i8], [12 x i8]* @.str.7, i64 0, i64 0), %sw.bb2 ], [ getelementptr inbounds ([12 x i8], [12 x i8]* @.str.7, i64 0, i64 0), %sw.bb1 ], [ getelementptr inbounds ([12 x i8], [12 x i8]* @.str.7, i64 0, i64 0), %sw.bb ]
+ %str2.0 = phi i8* [ getelementptr inbounds ([5 x i8], [5 x i8]* @.str.6, i64 0, i64 0), %entry ], [ getelementptr inbounds ([4 x i8], [4 x i8]* @.str.2, i64 0, i64 0), %sw.bb2 ], [ getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0), %sw.bb1 ], [ getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), %sw.bb ]
+ ret void
+}
+
+!llvm.module.flags = !{!0, !1}
+!0 = !{i32 7, !"PIC Level", i32 2}
+!1 = !{i32 1, !"Code Model", i32 1}
Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -5297,13 +5297,12 @@
/// Build instructions with Builder to retrieve the value at
/// the position given by Index in the lookup table.
- Value *BuildLookup(Value *Index, IRBuilder<> &Builder);
+ Value *BuildLookup(Value *Index, Type *ValueType, IRBuilder<> &Builder);
/// Return true if a table with TableSize elements of
/// type ElementType would fit in a target-legal register.
static bool WouldFitInRegister(const DataLayout &DL, uint64_t TableSize,
Type *ElementType);
-
private:
// Depending on the contents of the table, it can be represented in
// different ways.
@@ -5324,7 +5323,12 @@
// The table is stored as an array of values. Values are retrieved by load
// instructions from the table.
- ArrayKind
+ ArrayKind,
+
+ // The table is stored as an array of relative offsets between
+ // the lookup table and case results.
+ // Values are retrieved by shift and load.relative intrinsic call.
+ RelOffsetArrayKind
} Kind;
// For SingleValueKind, this is the single value.
@@ -5340,6 +5344,15 @@
// For ArrayKind, this is the array.
GlobalVariable *Array = nullptr;
+
+ /// Determines whether a relative table should be generated.
+ static bool ShouldBuildRelLookupTable(
+ Module &M,
+ const SmallVectorImpl<std::pair<ConstantInt *, Constant *>> &Values);
+
+ /// Generate an offset between the lookup table and given case result.
+ static Constant *GenerateRelOffset(Module &M, GlobalVariable *Array,
+ Constant *CaseRes);
};
} // end anonymous namespace
@@ -5447,21 +5460,111 @@
return;
}
- // Store the table in an array.
- ArrayType *ArrayTy = ArrayType::get(ValueType, TableSize);
- Constant *Initializer = ConstantArray::get(ArrayTy, TableContents);
+ // Check if relative lookup table should be generated.
+ if (ShouldBuildRelLookupTable(M, Values)) {
+ ArrayType *ArrayTy =
+ ArrayType::get(Type::getInt32Ty(M.getContext()), TableSize);
+
+ Array = new GlobalVariable(M, ArrayTy, /*isConstant=*/true,
+ GlobalVariable::PrivateLinkage, nullptr,
+ "switch.reltable." + FuncName);
+
+ for (size_t I = 0, E = Values.size(); I != E; ++I) {
+ ConstantInt *CaseVal = Values[I].first;
+ Constant *CaseRes = Values[I].second;
+ uint64_t Idx =
+ (CaseVal->getValue() - Offset->getValue()).getLimitedValue();
+
+ // If relative lookup table is enabled, put relative offsets into table.
+ TableContents[Idx] = GenerateRelOffset(M, Array, CaseRes);
+ }
+
+ if (Values.size() < TableSize) {
+ Constant *DefaultValueOffset = GenerateRelOffset(M, Array, DefaultValue);
+ for (uint64_t I = 0; I < TableSize; ++I) {
+ if (TableContents[I] == DefaultValue)
+ TableContents[I] = DefaultValueOffset;
+ }
+ }
- Array = new GlobalVariable(M, ArrayTy, /*isConstant=*/true,
- GlobalVariable::PrivateLinkage, Initializer,
- "switch.table." + FuncName);
- Array->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
- // Set the alignment to that of an array items. We will be only loading one
- // value out of it.
- Array->setAlignment(Align(DL.getPrefTypeAlignment(ValueType)));
- Kind = ArrayKind;
+ Constant *Initializer = ConstantArray::get(ArrayTy, TableContents);
+ Array->setInitializer(Initializer);
+ Array->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
+ Array->setAlignment(
+ Align(DL.getPrefTypeAlignment(Type::getInt32Ty(M.getContext()))));
+ Kind = RelOffsetArrayKind;
+ } else {
+ // Store the table in an array.
+ ArrayType *ArrayTy = ArrayType::get(ValueType, TableSize);
+ Constant *Initializer = ConstantArray::get(ArrayTy, TableContents);
+ Array = new GlobalVariable(M, ArrayTy, /*isConstant=*/true,
+ GlobalVariable::PrivateLinkage, Initializer,
+ "switch.table." + FuncName);
+ Array->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
+ Array->setAlignment(Align(DL.getPrefTypeAlignment(ValueType)));
+ Kind = ArrayKind;
+ }
}
-Value *SwitchLookupTable::BuildLookup(Value *Index, IRBuilder<> &Builder) {
+bool SwitchLookupTable::ShouldBuildRelLookupTable(
+ Module &M,
+ const SmallVectorImpl<std::pair<ConstantInt *, Constant *>> &Values) {
+ // If not in x86 or aarch64 mode, do not generate a relative lookup table.
+ Triple TargetTriple(M.getTargetTriple());
+ if (!(TargetTriple.getArch() == Triple::x86_64 ||
+ TargetTriple.getArch() == Triple::aarch64))
+ return false;
+
+ // If not tiny or small code model, do not generate a relative lookup table.
+ Optional<CodeModel::Model> CodeModel = M.getCodeModel();
+ if (!(CodeModel == CodeModel::Tiny || CodeModel == CodeModel::Small))
+ return false;
+
+ // If not in PIC mode, do not generate a relative lookup table.
+ if (M.getPICLevel() == PICLevel::NotPIC)
+ return false;
+
+ Type *ValueType = Values.begin()->second->getType();
+ // If values are not pointers, do not generate a relative lookup table.
+ if (!ValueType->isPointerTy())
+ return false;
+
+ /// If any of the pointer values is not a global value and dso_local,
+ /// do not generate a relative lookup table.
+ for (size_t I = 0, E = Values.size(); I != E; ++I) {
+ Constant *CaseRes = Values[I].second;
+ GlobalValue *GlobalVal = dyn_cast<GlobalValue>(CaseRes);
+
+ // Handle a constantexpr gep.
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(CaseRes)) {
+ if (CE->getOpcode() == Instruction::GetElementPtr)
+ GlobalVal = dyn_cast<GlobalValue>(CE->getOperand(0));
+ }
+
+ /// If any of the pointer values is not a global value or is not dso_local,
+ /// do not generate a relative lookup table.
+ if (GlobalVal == nullptr)
+ return false;
+ else if (!(GlobalVal->isDSOLocal() ||
+ GlobalValue::isLocalLinkage(GlobalVal->getLinkage())))
+ return false;
+ }
+
+ return true;
+}
+
+Constant *SwitchLookupTable::GenerateRelOffset(Module &M, GlobalVariable *Array,
+ Constant *CaseRes) {
+ Type *IntPtrTy = M.getDataLayout().getIntPtrType(M.getContext());
+ Constant *Base = llvm::ConstantExpr::getPtrToInt(Array, IntPtrTy);
+ Constant *Target = llvm::ConstantExpr::getPtrToInt(CaseRes, IntPtrTy);
+ Constant *RelOffset = llvm::ConstantExpr::getSub(Target, Base);
+ return llvm::ConstantExpr::getTrunc(RelOffset,
+ Type::getInt32Ty(M.getContext()));
+}
+
+Value *SwitchLookupTable::BuildLookup(Value *Index, Type *ValueType,
+ IRBuilder<> &Builder) {
switch (Kind) {
case SingleValueKind:
return SingleValue;
@@ -5495,7 +5598,8 @@
// Mask off.
return Builder.CreateTrunc(DownShifted, BitMapElementTy, "switch.masked");
}
- case ArrayKind: {
+ case ArrayKind:
+ case RelOffsetArrayKind: {
// Make sure the table index will not overflow when treated as signed.
IntegerType *IT = cast<IntegerType>(Index->getType());
uint64_t TableSize =
@@ -5505,12 +5609,31 @@
Index, IntegerType::get(IT->getContext(), IT->getBitWidth() + 1),
"switch.tableidx.zext");
- Value *GEPIndices[] = {Builder.getInt32(0), Index};
- Value *GEP = Builder.CreateInBoundsGEP(Array->getValueType(), Array,
- GEPIndices, "switch.gep");
- return Builder.CreateLoad(
- cast<ArrayType>(Array->getValueType())->getElementType(), GEP,
- "switch.load");
+ if (Kind == ArrayKind) {
+ Value *GEPIndices[] = {Builder.getInt32(0), Index};
+ Value *GEP = Builder.CreateInBoundsGEP(Array->getValueType(), Array,
+ GEPIndices, "switch.gep");
+ return Builder.CreateLoad(
+ cast<ArrayType>(Array->getValueType())->getElementType(), GEP,
+ "switch.load");
+ } else {
+ Constant *Base =
+ llvm::ConstantExpr::getBitCast(Array, Builder.getInt8PtrTy());
+
+ // Shift index by 2 to compute the offset.
+ Value *Offset = Builder.CreateLShr(Index, Builder.getInt32(2),
+ "switch.reltable.shift");
+
+ llvm::Module *Module = Builder.GetInsertBlock()->getModule();
+ Function *LoadRelIntrinsic = llvm::Intrinsic::getDeclaration(
+ Module, Intrinsic::load_relative, {Index->getType()});
+
+ // Call load relative intrinsic that computes the target address
+ // by adding base address (lookup table address) and relative offset.
+ Value *Call = Builder.CreateCall(LoadRelIntrinsic, {Base, Offset},
+ "switch.reltable.intrinsic");
+ return Builder.CreateBitCast(Call, ValueType);
+ }
}
}
llvm_unreachable("Unknown lookup table kind!");
@@ -5864,7 +5987,8 @@
SwitchLookupTable Table(Mod, TableSize, MinCaseVal, ResultList, DV, DL,
FuncName);
- Value *Result = Table.BuildLookup(TableIndex, Builder);
+ Type *ValueType = ResultList.begin()->second->getType();
+ Value *Result = Table.BuildLookup(TableIndex, ValueType, Builder);
// If the result is used to return immediately from the function, we want to
// do that right here.
Index: clang/test/CodeGen/switch-to-lookup-table.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/switch-to-lookup-table.c
@@ -0,0 +1,55 @@
+// Check switch to lookup optimization in fPIC and fno-PIC mode
+// RUN: %clang %s -target x86_64-linux -O2 -fno-PIC -fno-discard-value-names -S -emit-llvm -o - | FileCheck %s --check-prefix=FNOPIC
+// RUN: %clang %s -target x86_64-linux -O2 -fPIC -fno-discard-value-names -mcmodel=small -S -emit-llvm -o - | FileCheck %s --check-prefix=FPIC
+
+// Switch lookup table
+// FNOPIC: @switch.table.string_table = private unnamed_addr constant [3 x i8*]
+// FNOPIC-SAME: [
+// FNOPIC-SAME: i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0),
+// FNOPIC-SAME: i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0),
+// FNOPIC-SAME: i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.2, i64 0, i64 0)
+// FNOPIC-SAME: ], align 8
+
+// Relative switch lookup table
+// FPIC: @switch.reltable.string_table = private unnamed_addr constant [3 x i32]
+// FPIC-SAME: [
+// FPIC-SAME: i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str to i64), i64 ptrtoint ([3 x i32]* @switch.reltable.string_table to i64)) to i32),
+// FPIC-SAME: i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.1 to i64), i64 ptrtoint ([3 x i32]* @switch.reltable.string_table to i64)) to i32),
+// FPIC-SAME: i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.2 to i64), i64 ptrtoint ([3 x i32]* @switch.reltable.string_table to i64)) to i32)
+// FPIC-SAME: ], align 4
+char* string_table(int cond)
+{
+ // FNOPIC-LABEL: @string_table(
+ // FNOPIC-NEXT: entry:
+ // FNOPIC-NEXT: [[TMP0:%.*]] = icmp ult i32 [[COND:%.*]], 3
+ // FNOPIC-NEXT: br i1 [[TMP0]], label [[SWITCH_LOOKUP:%.*]], label [[RETURN:%.*]]
+ // FNOPIC: switch.lookup:
+ // FNOPIC-NEXT: [[TMP1:%.*]] = sext i32 %cond to i64
+ // FNOPIC-NEXT: [[SWITCH_GEP:%.*]] = getelementptr inbounds [3 x i8*], [3 x i8*]* @switch.table.string_table, i64 0, i64 [[TMP1]]
+ // FNOPIC-NEXT: [[SWITCH_LOAD:%.*]] = load i8*, i8** [[SWITCH_GEP]], align 8
+ // FNOPIC-NEXT: ret i8* [[SWITCH_LOAD]]
+ // FNOPIC: return:
+ // FNOPIC-NEXT: ret i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.3, i64 0, i64 0)
+
+ // FPIC-LABEL: @string_table(
+ // FPIC-NEXT: entry:
+ // FPIC-NEXT: [[TMP0:%.*]] = icmp ult i32 [[COND:%.*]], 3
+ // FPIC-NEXT: br i1 [[TMP0]], label [[SWITCH_LOOKUP:%.*]], label [[RETURN:%.*]]
+ // FPIC: switch.lookup:
+ // FPIC-NEXT: [[SWITCH_RELTABLE_SHIFT:%.*]] = lshr i32 %cond, 2
+ // FPIC-NEXT: [[SWITCH_RELTABLE_INTRINSIC:%.*]] = call i8* @llvm.load.relative.i32(i8* bitcast ([3 x i32]* @switch.reltable.string_table to i8*), i32 [[SWITCH_RELTABLE_SHIFT]])
+ // FPIC-NEXT: ret i8* [[SWITCH_RELTABLE_INTRINSIC]]
+ // FPIC: return:
+ // FPIC-NEXT: ret i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str.3, i64 0, i64 0)
+
+ switch (cond) {
+ case 0:
+ return "zero";
+ case 1:
+ return "one";
+ case 2:
+ return "two";
+ default:
+ return "default";
+ }
+}
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