From d8ae3e1feec0fa1c06e96e43a80ad2c5e5208461 Mon Sep 17 00:00:00 2001 From: Peter Collingbourne Date: Tue, 30 Dec 2014 20:05:19 +0000 Subject: [PATCH] x86_64: Fix calls to __morestack under the large code model. Under the large code model, we cannot assume that __morestack lives within 2^31 bytes of the call site, so we cannot use pc-relative addressing. We cannot perform the call via a temporary register, as the rax register may be used to store the static chain, and all other suitable registers may be either callee-save or used for parameter passing. We cannot use the stack at this point either because __morestack manipulates the stack directly. To avoid these issues, perform an indirect call via a read-only memory location containing the address. This solution is not perfect, as it assumes that the .rodata section is laid out within 2^31 bytes of each function body, but this seems to be sufficient for JIT. Differential Revision: http://reviews.llvm.org/D6787 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225003 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/llvm/CodeGen/MachineModuleInfo.h | 15 ++++++++++ lib/CodeGen/AsmPrinter/AsmPrinter.cpp | 17 +++++++++++ lib/CodeGen/MachineModuleInfo.cpp | 2 +- lib/Target/X86/X86FrameLowering.cpp | 36 ++++++++++++++++++++---- test/CodeGen/X86/segmented-stacks.ll | 15 ++++++++++ 5 files changed, 78 insertions(+), 7 deletions(-) diff --git a/include/llvm/CodeGen/MachineModuleInfo.h b/include/llvm/CodeGen/MachineModuleInfo.h index 287b3ebb0e2..584ce65c9d1 100644 --- a/include/llvm/CodeGen/MachineModuleInfo.h +++ b/include/llvm/CodeGen/MachineModuleInfo.h @@ -161,6 +161,13 @@ class MachineModuleInfo : public ImmutablePass { /// to _fltused on Windows targets. bool UsesVAFloatArgument; + /// UsesMorestackAddr - True if the module calls the __morestack function + /// indirectly, as is required under the large code model on x86. This is used + /// to emit a definition of a symbol, __morestack_addr, containing the + /// address. See comments in lib/Target/X86/X86FrameLowering.cpp for more + /// details. + bool UsesMorestackAddr; + public: static char ID; // Pass identification, replacement for typeid @@ -234,6 +241,14 @@ public: UsesVAFloatArgument = b; } + bool usesMorestackAddr() const { + return UsesMorestackAddr; + } + + void setUsesMorestackAddr(bool b) { + UsesMorestackAddr = b; + } + /// \brief Returns a reference to a list of cfi instructions in the current /// function's prologue. Used to construct frame maps for debug and exception /// handling comsumers. diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp index 97ef12c8328..ff8fc60e603 100644 --- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp +++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp @@ -1011,6 +1011,23 @@ bool AsmPrinter::doFinalization(Module &M) { // Emit llvm.ident metadata in an '.ident' directive. EmitModuleIdents(M); + // Emit __morestack address if needed for indirect calls. + if (MMI->usesMorestackAddr()) { + const MCSection *ReadOnlySection = + getObjFileLowering().getSectionForConstant(SectionKind::getReadOnly(), + /*C=*/nullptr); + OutStreamer.SwitchSection(ReadOnlySection); + + MCSymbol *AddrSymbol = + OutContext.GetOrCreateSymbol(StringRef("__morestack_addr")); + OutStreamer.EmitLabel(AddrSymbol); + + const DataLayout &DL = *TM.getSubtargetImpl()->getDataLayout(); + unsigned PtrSize = DL.getPointerSize(0); + OutStreamer.EmitSymbolValue(GetExternalSymbolSymbol("__morestack"), + PtrSize); + } + // If we don't have any trampolines, then we don't require stack memory // to be executable. Some targets have a directive to declare this. Function *InitTrampolineIntrinsic = M.getFunction("llvm.init.trampoline"); diff --git a/lib/CodeGen/MachineModuleInfo.cpp b/lib/CodeGen/MachineModuleInfo.cpp index eb3c0bf224d..baad411e2c5 100644 --- a/lib/CodeGen/MachineModuleInfo.cpp +++ b/lib/CodeGen/MachineModuleInfo.cpp @@ -273,7 +273,7 @@ bool MachineModuleInfo::doInitialization(Module &M) { CurCallSite = 0; CallsEHReturn = 0; CallsUnwindInit = 0; - DbgInfoAvailable = UsesVAFloatArgument = false; + DbgInfoAvailable = UsesVAFloatArgument = UsesMorestackAddr = false; // Always emit some info, by default "no personality" info. Personalities.push_back(nullptr); AddrLabelSymbols = nullptr; diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp index c408fddf890..95bca7d936f 100644 --- a/lib/Target/X86/X86FrameLowering.cpp +++ b/lib/Target/X86/X86FrameLowering.cpp @@ -1648,12 +1648,36 @@ X86FrameLowering::adjustForSegmentedStacks(MachineFunction &MF) const { } // __morestack is in libgcc - if (Is64Bit) - BuildMI(allocMBB, DL, TII.get(X86::CALL64pcrel32)) - .addExternalSymbol("__morestack"); - else - BuildMI(allocMBB, DL, TII.get(X86::CALLpcrel32)) - .addExternalSymbol("__morestack"); + if (Is64Bit && MF.getTarget().getCodeModel() == CodeModel::Large) { + // Under the large code model, we cannot assume that __morestack lives + // within 2^31 bytes of the call site, so we cannot use pc-relative + // addressing. We cannot perform the call via a temporary register, + // as the rax register may be used to store the static chain, and all + // other suitable registers may be either callee-save or used for + // parameter passing. We cannot use the stack at this point either + // because __morestack manipulates the stack directly. + // + // To avoid these issues, perform an indirect call via a read-only memory + // location containing the address. + // + // This solution is not perfect, as it assumes that the .rodata section + // is laid out within 2^31 bytes of each function body, but this seems + // to be sufficient for JIT. + BuildMI(allocMBB, DL, TII.get(X86::CALL64m)) + .addReg(X86::RIP) + .addImm(0) + .addReg(0) + .addExternalSymbol("__morestack_addr") + .addReg(0); + MF.getMMI().setUsesMorestackAddr(true); + } else { + if (Is64Bit) + BuildMI(allocMBB, DL, TII.get(X86::CALL64pcrel32)) + .addExternalSymbol("__morestack"); + else + BuildMI(allocMBB, DL, TII.get(X86::CALLpcrel32)) + .addExternalSymbol("__morestack"); + } if (IsNested) BuildMI(allocMBB, DL, TII.get(X86::MORESTACK_RET_RESTORE_R10)); diff --git a/test/CodeGen/X86/segmented-stacks.ll b/test/CodeGen/X86/segmented-stacks.ll index 45e157ff7c7..3e47121a380 100644 --- a/test/CodeGen/X86/segmented-stacks.ll +++ b/test/CodeGen/X86/segmented-stacks.ll @@ -1,5 +1,6 @@ ; RUN: llc < %s -mcpu=generic -mtriple=i686-linux -verify-machineinstrs | FileCheck %s -check-prefix=X32-Linux ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-linux -verify-machineinstrs | FileCheck %s -check-prefix=X64-Linux +; RUN: llc < %s -mcpu=generic -mtriple=x86_64-linux -code-model=large -verify-machineinstrs | FileCheck %s -check-prefix=X64-Linux-Large ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-linux-gnux32 -verify-machineinstrs | FileCheck %s -check-prefix=X32ABI ; RUN: llc < %s -mcpu=generic -mtriple=i686-darwin -verify-machineinstrs | FileCheck %s -check-prefix=X32-Darwin ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-darwin -verify-machineinstrs | FileCheck %s -check-prefix=X64-Darwin @@ -57,6 +58,16 @@ define void @test_basic() #0 { ; X64-Linux-NEXT: callq __morestack ; X64-Linux-NEXT: ret +; X64-Linux-Large-LABEL: test_basic: + +; X64-Linux-Large: cmpq %fs:112, %rsp +; X64-Linux-Large-NEXT: ja .LBB0_2 + +; X64-Linux-Large: movabsq $40, %r10 +; X64-Linux-Large-NEXT: movabsq $0, %r11 +; X64-Linux-Large-NEXT: callq *__morestack_addr(%rip) +; X64-Linux-Large-NEXT: ret + ; X32ABI-LABEL: test_basic: ; X32ABI: cmpl %fs:64, %esp @@ -626,3 +637,7 @@ define void @test_nostack() #0 { } attributes #0 = { "split-stack" } + +; X64-Linux-Large: .rodata +; X64-Linux-Large-NEXT: __morestack_addr: +; X64-Linux-Large-NEXT: .quad __morestack -- 2.34.1