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09f505a0a5
llvm/lib/MC/MCWin64EH.cpp
Saleem Abdulrasool 09f505a0a5 MC: add and use an accessor for WinCFI 
This adds a utility method to access the WinCFI information in bulk and uses
that to iterate rather than requesting the count and individually iterating
them.  This is in preparation for restructuring WinCFI handling to enable more
clear sharing across architectures to enable unwind information emission for
Windows on ARM.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212683 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-10 04:50:06 +00:00

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//===- lib/MC/MCWin64EH.cpp - MCWin64EH implementation --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCWin64EH.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
namespace llvm {
// NOTE: All relocations generated here are 4-byte image-relative.
static uint8_t CountOfUnwindCodes(std::vector<MCWin64EHInstruction> &instArray){
uint8_t count = 0;
for (std::vector<MCWin64EHInstruction>::const_iterator I = instArray.begin(),
E = instArray.end(); I != E; ++I) {
switch (I->getOperation()) {
case Win64EH::UOP_PushNonVol:
case Win64EH::UOP_AllocSmall:
case Win64EH::UOP_SetFPReg:
case Win64EH::UOP_PushMachFrame:
count += 1;
break;
case Win64EH::UOP_SaveNonVol:
case Win64EH::UOP_SaveXMM128:
count += 2;
break;
case Win64EH::UOP_SaveNonVolBig:
case Win64EH::UOP_SaveXMM128Big:
count += 3;
break;
case Win64EH::UOP_AllocLarge:
if (I->getSize() > 512*1024-8)
count += 3;
else
count += 2;
break;
}
}
return count;
}
static void EmitAbsDifference(MCStreamer &streamer, MCSymbol *lhs,
MCSymbol *rhs) {
MCContext &context = streamer.getContext();
const MCExpr *diff = MCBinaryExpr::CreateSub(MCSymbolRefExpr::Create(
lhs, context),
MCSymbolRefExpr::Create(
rhs, context),
context);
streamer.EmitAbsValue(diff, 1);
}
static void EmitUnwindCode(MCStreamer &streamer, MCSymbol *begin,
MCWin64EHInstruction &inst) {
uint8_t b2;
uint16_t w;
b2 = (inst.getOperation() & 0x0F);
switch (inst.getOperation()) {
case Win64EH::UOP_PushNonVol:
EmitAbsDifference(streamer, inst.getLabel(), begin);
b2 |= (inst.getRegister() & 0x0F) << 4;
streamer.EmitIntValue(b2, 1);
break;
case Win64EH::UOP_AllocLarge:
EmitAbsDifference(streamer, inst.getLabel(), begin);
if (inst.getSize() > 512*1024-8) {
b2 |= 0x10;
streamer.EmitIntValue(b2, 1);
w = inst.getSize() & 0xFFF8;
streamer.EmitIntValue(w, 2);
w = inst.getSize() >> 16;
} else {
streamer.EmitIntValue(b2, 1);
w = inst.getSize() >> 3;
}
streamer.EmitIntValue(w, 2);
break;
case Win64EH::UOP_AllocSmall:
b2 |= (((inst.getSize()-8) >> 3) & 0x0F) << 4;
EmitAbsDifference(streamer, inst.getLabel(), begin);
streamer.EmitIntValue(b2, 1);
break;
case Win64EH::UOP_SetFPReg:
EmitAbsDifference(streamer, inst.getLabel(), begin);
streamer.EmitIntValue(b2, 1);
break;
case Win64EH::UOP_SaveNonVol:
case Win64EH::UOP_SaveXMM128:
b2 |= (inst.getRegister() & 0x0F) << 4;
EmitAbsDifference(streamer, inst.getLabel(), begin);
streamer.EmitIntValue(b2, 1);
w = inst.getOffset() >> 3;
if (inst.getOperation() == Win64EH::UOP_SaveXMM128)
w >>= 1;
streamer.EmitIntValue(w, 2);
break;
case Win64EH::UOP_SaveNonVolBig:
case Win64EH::UOP_SaveXMM128Big:
b2 |= (inst.getRegister() & 0x0F) << 4;
EmitAbsDifference(streamer, inst.getLabel(), begin);
streamer.EmitIntValue(b2, 1);
if (inst.getOperation() == Win64EH::UOP_SaveXMM128Big)
w = inst.getOffset() & 0xFFF0;
else
w = inst.getOffset() & 0xFFF8;
streamer.EmitIntValue(w, 2);
w = inst.getOffset() >> 16;
streamer.EmitIntValue(w, 2);
break;
case Win64EH::UOP_PushMachFrame:
if (inst.isPushCodeFrame())
b2 |= 0x10;
EmitAbsDifference(streamer, inst.getLabel(), begin);
streamer.EmitIntValue(b2, 1);
break;
}
}
static void EmitSymbolRefWithOfs(MCStreamer &streamer,
const MCSymbol *Base,
const MCSymbol *Other) {
MCContext &Context = streamer.getContext();
const MCSymbolRefExpr *BaseRef = MCSymbolRefExpr::Create(Base, Context);
const MCSymbolRefExpr *OtherRef = MCSymbolRefExpr::Create(Other, Context);
const MCExpr *Ofs = MCBinaryExpr::CreateSub(OtherRef, BaseRef, Context);
const MCSymbolRefExpr *BaseRefRel = MCSymbolRefExpr::Create(Base,
MCSymbolRefExpr::VK_COFF_IMGREL32,
Context);
streamer.EmitValue(MCBinaryExpr::CreateAdd(BaseRefRel, Ofs, Context), 4);
}
static void EmitRuntimeFunction(MCStreamer &streamer,
const MCWin64EHUnwindInfo *info) {
MCContext &context = streamer.getContext();
streamer.EmitValueToAlignment(4);
EmitSymbolRefWithOfs(streamer, info->Function, info->Begin);
EmitSymbolRefWithOfs(streamer, info->Function, info->End);
streamer.EmitValue(MCSymbolRefExpr::Create(info->Symbol,
MCSymbolRefExpr::VK_COFF_IMGREL32,
context), 4);
}
static void EmitUnwindInfo(MCStreamer &streamer, MCWin64EHUnwindInfo *info) {
// If this UNWIND_INFO already has a symbol, it's already been emitted.
if (info->Symbol) return;
MCContext &context = streamer.getContext();
streamer.EmitValueToAlignment(4);
info->Symbol = context.CreateTempSymbol();
streamer.EmitLabel(info->Symbol);
// Upper 3 bits are the version number (currently 1).
uint8_t flags = 0x01;
if (info->ChainedParent)
flags |= Win64EH::UNW_ChainInfo << 3;
else {
if (info->HandlesUnwind)
flags |= Win64EH::UNW_TerminateHandler << 3;
if (info->HandlesExceptions)
flags |= Win64EH::UNW_ExceptionHandler << 3;
}
streamer.EmitIntValue(flags, 1);
if (info->PrologEnd)
EmitAbsDifference(streamer, info->PrologEnd, info->Begin);
else
streamer.EmitIntValue(0, 1);
uint8_t numCodes = CountOfUnwindCodes(info->Instructions);
streamer.EmitIntValue(numCodes, 1);
uint8_t frame = 0;
if (info->LastFrameInst >= 0) {
MCWin64EHInstruction &frameInst = info->Instructions[info->LastFrameInst];
assert(frameInst.getOperation() == Win64EH::UOP_SetFPReg);
frame = (frameInst.getRegister() & 0x0F) |
(frameInst.getOffset() & 0xF0);
}
streamer.EmitIntValue(frame, 1);
// Emit unwind instructions (in reverse order).
uint8_t numInst = info->Instructions.size();
for (uint8_t c = 0; c < numInst; ++c) {
MCWin64EHInstruction inst = info->Instructions.back();
info->Instructions.pop_back();
EmitUnwindCode(streamer, info->Begin, inst);
}
// For alignment purposes, the instruction array will always have an even
// number of entries, with the final entry potentially unused (in which case
// the array will be one longer than indicated by the count of unwind codes
// field).
if (numCodes & 1) {
streamer.EmitIntValue(0, 2);
}
if (flags & (Win64EH::UNW_ChainInfo << 3))
EmitRuntimeFunction(streamer, info->ChainedParent);
else if (flags &
((Win64EH::UNW_TerminateHandler|Win64EH::UNW_ExceptionHandler) << 3))
streamer.EmitValue(MCSymbolRefExpr::Create(info->ExceptionHandler,
MCSymbolRefExpr::VK_COFF_IMGREL32,
context), 4);
else if (numCodes == 0) {
// The minimum size of an UNWIND_INFO struct is 8 bytes. If we're not
// a chained unwind info, if there is no handler, and if there are fewer
// than 2 slots used in the unwind code array, we have to pad to 8 bytes.
streamer.EmitIntValue(0, 4);
}
}
StringRef MCWin64EHUnwindEmitter::GetSectionSuffix(const MCSymbol *func) {
if (!func || !func->isInSection()) return "";
const MCSection *section = &func->getSection();
const MCSectionCOFF *COFFSection;
if ((COFFSection = dyn_cast<MCSectionCOFF>(section))) {
StringRef name = COFFSection->getSectionName();
size_t dollar = name.find('$');
size_t dot = name.find('.', 1);
if (dollar == StringRef::npos && dot == StringRef::npos)
return "";
if (dot == StringRef::npos)
return name.substr(dollar);
if (dollar == StringRef::npos || dot < dollar)
return name.substr(dot);
return name.substr(dollar);
}
return "";
}
static const MCSection *getWin64EHTableSection(StringRef suffix,
MCContext &context) {
if (suffix == "")
return context.getObjectFileInfo()->getXDataSection();
return context.getCOFFSection((".xdata"+suffix).str(),
COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ,
SectionKind::getDataRel());
}
static const MCSection *getWin64EHFuncTableSection(StringRef suffix,
MCContext &context) {
if (suffix == "")
return context.getObjectFileInfo()->getPDataSection();
return context.getCOFFSection((".pdata"+suffix).str(),
COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ,
SectionKind::getDataRel());
}
void MCWin64EHUnwindEmitter::EmitUnwindInfo(MCStreamer &streamer,
MCWin64EHUnwindInfo *info) {
// Switch sections (the static function above is meant to be called from
// here and from Emit().
MCContext &context = streamer.getContext();
const MCSection *xdataSect =
getWin64EHTableSection(GetSectionSuffix(info->Function), context);
streamer.SwitchSection(xdataSect);
llvm::EmitUnwindInfo(streamer, info);
}
void MCWin64EHUnwindEmitter::Emit(MCStreamer &Streamer) {
MCContext &Context = Streamer.getContext();
// Emit the unwind info structs first.
for (const auto &CFI : Streamer.getW64UnwindInfos()) {
const MCSection *XData =
getWin64EHTableSection(GetSectionSuffix(CFI->Function), Context);
Streamer.SwitchSection(XData);
EmitUnwindInfo(Streamer, CFI);
}
// Now emit RUNTIME_FUNCTION entries.
for (const auto &CFI : Streamer.getW64UnwindInfos()) {
const MCSection *PData =
getWin64EHFuncTableSection(GetSectionSuffix(CFI->Function), Context);
Streamer.SwitchSection(PData);
EmitRuntimeFunction(Streamer, CFI);
}
}
} // End of namespace llvm
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