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author | Michael Platings <michael.platings@arm.com> | 2019-03-06 17:24:11 +0000 |
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committer | Michael Platings <michael.platings@arm.com> | 2019-03-06 17:24:11 +0000 |
commit | 2391bfca97290181ae65796ea6da135d1b6d037b (patch) | |
tree | c6d06bb3c64c5eddaf4aac60e06932443cd0ce99 /llvm | |
parent | 930007ba761badbcd7fe9abf20e3a36b696f98d6 (diff) | |
download | bcm5719-llvm-2391bfca97290181ae65796ea6da135d1b6d037b.tar.gz bcm5719-llvm-2391bfca97290181ae65796ea6da135d1b6d037b.zip |
[IR][ARM] Add function pointer alignment to datalayout
Use this feature to fix a bug on ARM where 4 byte alignment is
incorrectly assumed.
Differential Revision: https://reviews.llvm.org/D57335
llvm-svn: 355522
Diffstat (limited to 'llvm')
-rw-r--r-- | llvm/docs/LangRef.rst | 8 | ||||
-rw-r--r-- | llvm/include/llvm/IR/DataLayout.h | 23 | ||||
-rw-r--r-- | llvm/lib/IR/ConstantFold.cpp | 28 | ||||
-rw-r--r-- | llvm/lib/IR/DataLayout.cpp | 20 | ||||
-rw-r--r-- | llvm/lib/IR/Value.cpp | 14 | ||||
-rw-r--r-- | llvm/lib/Target/ARM/ARMTargetMachine.cpp | 4 | ||||
-rw-r--r-- | llvm/unittests/IR/CMakeLists.txt | 1 | ||||
-rw-r--r-- | llvm/unittests/IR/ConstantsTest.cpp | 100 | ||||
-rw-r--r-- | llvm/unittests/IR/DataLayoutTest.cpp | 47 | ||||
-rw-r--r-- | llvm/unittests/IR/FunctionTest.cpp | 25 |
10 files changed, 262 insertions, 8 deletions
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst index 86972acf6ad..261d1d47d20 100644 --- a/llvm/docs/LangRef.rst +++ b/llvm/docs/LangRef.rst @@ -2004,6 +2004,14 @@ as follows: targets. ``a:<abi>:<pref>`` This specifies the alignment for an object of aggregate type. +``F<type><abi>`` + This specifies the alignment for function pointers. + The options for ``<type>`` are: + + * ``i``: The alignment of function pointers is independent of the alignment + of functions, and is a multiple of ``<abi>``. + * ``n``: The alignment of function pointers is a multiple of the explicit + alignment specified on the function, and is a multiple of ``<abi>``. ``m:<mangling>`` If present, specifies that llvm names are mangled in the output. Symbols prefixed with the mangling escape character ``\01`` are passed through diff --git a/llvm/include/llvm/IR/DataLayout.h b/llvm/include/llvm/IR/DataLayout.h index 869b27b1fda..05c72f10d30 100644 --- a/llvm/include/llvm/IR/DataLayout.h +++ b/llvm/include/llvm/IR/DataLayout.h @@ -108,6 +108,13 @@ struct PointerAlignElem { /// generating LLVM IR is required to generate the right target data for the /// target being codegen'd to. class DataLayout { +public: + enum class FunctionPtrAlignType { + /// The function pointer alignment is independent of the function alignment. + Independent, + /// The function pointer alignment is a multiple of the function alignment. + MultipleOfFunctionAlign, + }; private: /// Defaults to false. bool BigEndian; @@ -116,6 +123,9 @@ private: unsigned StackNaturalAlign; unsigned ProgramAddrSpace; + unsigned FunctionPtrAlign; + FunctionPtrAlignType TheFunctionPtrAlignType; + enum ManglingModeT { MM_None, MM_ELF, @@ -199,6 +209,8 @@ public: BigEndian = DL.isBigEndian(); AllocaAddrSpace = DL.AllocaAddrSpace; StackNaturalAlign = DL.StackNaturalAlign; + FunctionPtrAlign = DL.FunctionPtrAlign; + TheFunctionPtrAlignType = DL.TheFunctionPtrAlignType; ProgramAddrSpace = DL.ProgramAddrSpace; ManglingMode = DL.ManglingMode; LegalIntWidths = DL.LegalIntWidths; @@ -256,6 +268,17 @@ public: unsigned getStackAlignment() const { return StackNaturalAlign; } unsigned getAllocaAddrSpace() const { return AllocaAddrSpace; } + /// Returns the alignment of function pointers, which may or may not be + /// related to the alignment of functions. + /// \see getFunctionPtrAlignType + unsigned getFunctionPtrAlign() const { return FunctionPtrAlign; } + + /// Return the type of function pointer alignment. + /// \see getFunctionPtrAlign + FunctionPtrAlignType getFunctionPtrAlignType() const { + return TheFunctionPtrAlignType; + } + unsigned getProgramAddressSpace() const { return ProgramAddrSpace; } bool hasMicrosoftFastStdCallMangling() const { diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp index 037f120f47d..3784405ecb0 100644 --- a/llvm/lib/IR/ConstantFold.cpp +++ b/llvm/lib/IR/ConstantFold.cpp @@ -26,6 +26,7 @@ #include "llvm/IR/GlobalAlias.h" #include "llvm/IR/GlobalVariable.h" #include "llvm/IR/Instructions.h" +#include "llvm/IR/Module.h" #include "llvm/IR/Operator.h" #include "llvm/IR/PatternMatch.h" #include "llvm/Support/ErrorHandling.h" @@ -1076,10 +1077,29 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1, isa<GlobalValue>(CE1->getOperand(0))) { GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); - // Functions are at least 4-byte aligned. - unsigned GVAlign = GV->getAlignment(); - if (isa<Function>(GV)) - GVAlign = std::max(GVAlign, 4U); + unsigned GVAlign; + + if (Module *TheModule = GV->getParent()) { + GVAlign = GV->getPointerAlignment(TheModule->getDataLayout()); + + // If the function alignment is not specified then assume that it + // is 4. + // This is dangerous; on x86, the alignment of the pointer + // corresponds to the alignment of the function, but might be less + // than 4 if it isn't explicitly specified. + // However, a fix for this behaviour was reverted because it + // increased code size (see https://reviews.llvm.org/D55115) + // FIXME: This code should be deleted once existing targets have + // appropriate defaults + if (GVAlign == 0U && isa<Function>(GV)) + GVAlign = 4U; + } else if (isa<Function>(GV)) { + // Without a datalayout we have to assume the worst case: that the + // function pointer isn't aligned at all. + GVAlign = 0U; + } else { + GVAlign = GV->getAlignment(); + } if (GVAlign > 1) { unsigned DstWidth = CI2->getType()->getBitWidth(); diff --git a/llvm/lib/IR/DataLayout.cpp b/llvm/lib/IR/DataLayout.cpp index 2644214a49c..943f5381c64 100644 --- a/llvm/lib/IR/DataLayout.cpp +++ b/llvm/lib/IR/DataLayout.cpp @@ -184,6 +184,8 @@ void DataLayout::reset(StringRef Desc) { AllocaAddrSpace = 0; StackNaturalAlign = 0; ProgramAddrSpace = 0; + FunctionPtrAlign = 0; + TheFunctionPtrAlignType = FunctionPtrAlignType::Independent; ManglingMode = MM_None; NonIntegralAddressSpaces.clear(); @@ -379,6 +381,22 @@ void DataLayout::parseSpecifier(StringRef Desc) { StackNaturalAlign = inBytes(getInt(Tok)); break; } + case 'F': { + switch (Tok.front()) { + case 'i': + TheFunctionPtrAlignType = FunctionPtrAlignType::Independent; + break; + case 'n': + TheFunctionPtrAlignType = FunctionPtrAlignType::MultipleOfFunctionAlign; + break; + default: + report_fatal_error("Unknown function pointer alignment type in " + "datalayout string"); + } + Tok = Tok.substr(1); + FunctionPtrAlign = inBytes(getInt(Tok)); + break; + } case 'P': { // Function address space. ProgramAddrSpace = getAddrSpace(Tok); break; @@ -432,6 +450,8 @@ bool DataLayout::operator==(const DataLayout &Other) const { AllocaAddrSpace == Other.AllocaAddrSpace && StackNaturalAlign == Other.StackNaturalAlign && ProgramAddrSpace == Other.ProgramAddrSpace && + FunctionPtrAlign == Other.FunctionPtrAlign && + TheFunctionPtrAlignType == Other.TheFunctionPtrAlignType && ManglingMode == Other.ManglingMode && LegalIntWidths == Other.LegalIntWidths && Alignments == Other.Alignments && Pointers == Other.Pointers; diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp index 38eed76fe45..28263ede39d 100644 --- a/llvm/lib/IR/Value.cpp +++ b/llvm/lib/IR/Value.cpp @@ -648,10 +648,16 @@ unsigned Value::getPointerAlignment(const DataLayout &DL) const { unsigned Align = 0; if (auto *GO = dyn_cast<GlobalObject>(this)) { - // Don't make any assumptions about function pointer alignment. Some - // targets use the LSBs to store additional information. - if (isa<Function>(GO)) - return 0; + if (isa<Function>(GO)) { + switch (DL.getFunctionPtrAlignType()) { + case DataLayout::FunctionPtrAlignType::Independent: + return DL.getFunctionPtrAlign(); + case DataLayout::FunctionPtrAlignType::MultipleOfFunctionAlign: + return std::max(DL.getFunctionPtrAlign(), GO->getAlignment()); + default: + llvm_unreachable("unknown function pointer align type"); + } + } Align = GO->getAlignment(); if (Align == 0) { if (auto *GVar = dyn_cast<GlobalVariable>(GO)) { diff --git a/llvm/lib/Target/ARM/ARMTargetMachine.cpp b/llvm/lib/Target/ARM/ARMTargetMachine.cpp index 9954eee2e5f..401843c1e0f 100644 --- a/llvm/lib/Target/ARM/ARMTargetMachine.cpp +++ b/llvm/lib/Target/ARM/ARMTargetMachine.cpp @@ -141,6 +141,10 @@ static std::string computeDataLayout(const Triple &TT, StringRef CPU, // Pointers are 32 bits and aligned to 32 bits. Ret += "-p:32:32"; + // Function pointers are aligned to 8 bits (because the LSB stores the + // ARM/Thumb state). + Ret += "-Fi8"; + // ABIs other than APCS have 64 bit integers with natural alignment. if (ABI != ARMBaseTargetMachine::ARM_ABI_APCS) Ret += "-i64:64"; diff --git a/llvm/unittests/IR/CMakeLists.txt b/llvm/unittests/IR/CMakeLists.txt index a823407169f..c3cdf90c0ef 100644 --- a/llvm/unittests/IR/CMakeLists.txt +++ b/llvm/unittests/IR/CMakeLists.txt @@ -13,6 +13,7 @@ add_llvm_unittest(IRTests CFGBuilder.cpp ConstantRangeTest.cpp ConstantsTest.cpp + DataLayoutTest.cpp DebugInfoTest.cpp DebugTypeODRUniquingTest.cpp DominatorTreeTest.cpp diff --git a/llvm/unittests/IR/ConstantsTest.cpp b/llvm/unittests/IR/ConstantsTest.cpp index 6b26b38e35e..c0fe18b1182 100644 --- a/llvm/unittests/IR/ConstantsTest.cpp +++ b/llvm/unittests/IR/ConstantsTest.cpp @@ -475,5 +475,105 @@ TEST(ConstantsTest, BitcastToGEP) { ASSERT_EQ(cast<ConstantExpr>(C)->getOpcode(), Instruction::BitCast); } +bool foldFuncPtrAndConstToNull(LLVMContext &Context, Module *TheModule, + uint64_t AndValue, unsigned FunctionAlign = 0) { + Type *VoidType(Type::getVoidTy(Context)); + FunctionType *FuncType(FunctionType::get(VoidType, false)); + Function *Func(Function::Create( + FuncType, GlobalValue::ExternalLinkage, "", TheModule)); + + if (FunctionAlign) Func->setAlignment(FunctionAlign); + + IntegerType *ConstantIntType(Type::getInt32Ty(Context)); + ConstantInt *TheConstant(ConstantInt::get(ConstantIntType, AndValue)); + + Constant *TheConstantExpr( + ConstantExpr::getPtrToInt(Func, ConstantIntType)); + + return ConstantExpr::get(Instruction::And, TheConstantExpr, + TheConstant)->isNullValue(); +} + +TEST(ConstantsTest, FoldFunctionPtrAlignUnknownAnd2) { + LLVMContext Context; + Module TheModule("TestModule", Context); + // When the DataLayout doesn't specify a function pointer alignment we + // assume in this case that it is 4 byte aligned. This is a bug but we can't + // fix it directly because it causes a code size regression on X86. + // FIXME: This test should be changed once existing targets have + // appropriate defaults. See associated FIXME in ConstantFoldBinaryInstruction + ASSERT_TRUE(foldFuncPtrAndConstToNull(Context, &TheModule, 2)); +} + +TEST(ConstantsTest, DontFoldFunctionPtrAlignUnknownAnd4) { + LLVMContext Context; + Module TheModule("TestModule", Context); + ASSERT_FALSE(foldFuncPtrAndConstToNull(Context, &TheModule, 4)); +} + +TEST(ConstantsTest, FoldFunctionPtrAlign4) { + LLVMContext Context; + Module TheModule("TestModule", Context); + const char* AlignmentStrings[] = { "Fi32", "Fn32" }; + + for (unsigned AndValue = 1; AndValue <= 2; ++AndValue) { + for (const char *AlignmentString : AlignmentStrings) { + TheModule.setDataLayout(AlignmentString); + ASSERT_TRUE(foldFuncPtrAndConstToNull(Context, &TheModule, AndValue)); + } + } +} + +TEST(ConstantsTest, DontFoldFunctionPtrAlign1) { + LLVMContext Context; + Module TheModule("TestModule", Context); + const char* AlignmentStrings[] = { "Fi8", "Fn8" }; + + for (const char* AlignmentString : AlignmentStrings) { + TheModule.setDataLayout(AlignmentString); + ASSERT_FALSE(foldFuncPtrAndConstToNull(Context, &TheModule, 2)); + } +} + +TEST(ConstantsTest, FoldFunctionAlign4PtrAlignMultiple) { + LLVMContext Context; + Module TheModule("TestModule", Context); + TheModule.setDataLayout("Fn8"); + ASSERT_TRUE(foldFuncPtrAndConstToNull(Context, &TheModule, 2, 4)); +} + +TEST(ConstantsTest, DontFoldFunctionAlign4PtrAlignIndependent) { + LLVMContext Context; + Module TheModule("TestModule", Context); + TheModule.setDataLayout("Fi8"); + ASSERT_FALSE(foldFuncPtrAndConstToNull(Context, &TheModule, 2, 4)); +} + +TEST(ConstantsTest, DontFoldFunctionPtrIfNoModule) { + LLVMContext Context; + // Even though the function is explicitly 4 byte aligned, in the absence of a + // DataLayout we can't assume that the function pointer is aligned. + ASSERT_FALSE(foldFuncPtrAndConstToNull(Context, nullptr, 2, 4)); +} + +TEST(ConstantsTest, FoldGlobalVariablePtr) { + LLVMContext Context; + + + IntegerType *IntType(Type::getInt32Ty(Context)); + + GlobalVariable Global(IntType, true, GlobalValue::ExternalLinkage); + + Global.setAlignment(4); + + ConstantInt *TheConstant(ConstantInt::get(IntType, 2)); + + Constant *TheConstantExpr( + ConstantExpr::getPtrToInt(&Global, IntType)); + + ASSERT_TRUE(ConstantExpr::get( \ + Instruction::And, TheConstantExpr, TheConstant)->isNullValue()); +} + } // end anonymous namespace } // end namespace llvm diff --git a/llvm/unittests/IR/DataLayoutTest.cpp b/llvm/unittests/IR/DataLayoutTest.cpp new file mode 100644 index 00000000000..e7ed70b7de5 --- /dev/null +++ b/llvm/unittests/IR/DataLayoutTest.cpp @@ -0,0 +1,47 @@ +//===- ConstantRangeTest.cpp - ConstantRange tests ------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +#include "llvm/IR/DataLayout.h" +#include "gtest/gtest.h" + +using namespace llvm; + +namespace { + +TEST(DataLayoutTest, FunctionPtrAlign) { + EXPECT_EQ(0U, DataLayout("").getFunctionPtrAlign()); + EXPECT_EQ(1U, DataLayout("Fi8").getFunctionPtrAlign()); + EXPECT_EQ(2U, DataLayout("Fi16").getFunctionPtrAlign()); + EXPECT_EQ(4U, DataLayout("Fi32").getFunctionPtrAlign()); + EXPECT_EQ(8U, DataLayout("Fi64").getFunctionPtrAlign()); + EXPECT_EQ(1U, DataLayout("Fn8").getFunctionPtrAlign()); + EXPECT_EQ(2U, DataLayout("Fn16").getFunctionPtrAlign()); + EXPECT_EQ(4U, DataLayout("Fn32").getFunctionPtrAlign()); + EXPECT_EQ(8U, DataLayout("Fn64").getFunctionPtrAlign()); + EXPECT_EQ(DataLayout::FunctionPtrAlignType::Independent, \ + DataLayout("").getFunctionPtrAlignType()); + EXPECT_EQ(DataLayout::FunctionPtrAlignType::Independent, \ + DataLayout("Fi8").getFunctionPtrAlignType()); + EXPECT_EQ(DataLayout::FunctionPtrAlignType::MultipleOfFunctionAlign, \ + DataLayout("Fn8").getFunctionPtrAlignType()); + EXPECT_EQ(DataLayout("Fi8"), DataLayout("Fi8")); + EXPECT_NE(DataLayout("Fi8"), DataLayout("Fi16")); + EXPECT_NE(DataLayout("Fi8"), DataLayout("Fn8")); + + DataLayout a(""), b("Fi8"), c("Fn8"); + EXPECT_NE(a, b); + EXPECT_NE(a, c); + EXPECT_NE(b, c); + + a = b; + EXPECT_EQ(a, b); + a = c; + EXPECT_EQ(a, c); +} + +} // anonymous namespace diff --git a/llvm/unittests/IR/FunctionTest.cpp b/llvm/unittests/IR/FunctionTest.cpp index 10a359ff64b..c68b064afe3 100644 --- a/llvm/unittests/IR/FunctionTest.cpp +++ b/llvm/unittests/IR/FunctionTest.cpp @@ -129,4 +129,29 @@ TEST(FunctionTest, setSection) { EXPECT_TRUE(F->hasSection()); } +TEST(FunctionTest, GetPointerAlignment) { + LLVMContext Context; + Type *VoidType(Type::getVoidTy(Context)); + FunctionType *FuncType(FunctionType::get(VoidType, false)); + Function *Func = Function::Create( + FuncType, GlobalValue::ExternalLinkage); + EXPECT_EQ(0U, Func->getPointerAlignment(DataLayout(""))); + EXPECT_EQ(1U, Func->getPointerAlignment(DataLayout("Fi8"))); + EXPECT_EQ(1U, Func->getPointerAlignment(DataLayout("Fn8"))); + EXPECT_EQ(2U, Func->getPointerAlignment(DataLayout("Fi16"))); + EXPECT_EQ(2U, Func->getPointerAlignment(DataLayout("Fn16"))); + EXPECT_EQ(4U, Func->getPointerAlignment(DataLayout("Fi32"))); + EXPECT_EQ(4U, Func->getPointerAlignment(DataLayout("Fn32"))); + + Func->setAlignment(4U); + + EXPECT_EQ(0U, Func->getPointerAlignment(DataLayout(""))); + EXPECT_EQ(1U, Func->getPointerAlignment(DataLayout("Fi8"))); + EXPECT_EQ(4U, Func->getPointerAlignment(DataLayout("Fn8"))); + EXPECT_EQ(2U, Func->getPointerAlignment(DataLayout("Fi16"))); + EXPECT_EQ(4U, Func->getPointerAlignment(DataLayout("Fn16"))); + EXPECT_EQ(4U, Func->getPointerAlignment(DataLayout("Fi32"))); + EXPECT_EQ(4U, Func->getPointerAlignment(DataLayout("Fn32"))); +} + } // end namespace |