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Fix a bit of confusion about .set and produce more readable assembly.

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Every target we support has support for assembly that looks like

a = b - c
.long a

What is special about MachO is that the above combination suppresses the
production of a relocation.

With this change we avoid producing the intermediary labels when they don't
add any value.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220256 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola
2014-10-21 01:17:30 +00:00
parent f8c9d3d3c2
commit 45968c54e9
15 changed files with 63 additions and 91 deletions
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58
lib/CodeGen/AsmPrinter/AsmPrinter.cpp
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@@ -962,24 +962,21 @@ bool AsmPrinter::doFinalization(Module &M) {
}
}
if (MAI->hasSetDirective()) {
OutStreamer.AddBlankLine();
for (const auto &Alias : M.aliases()) {
MCSymbol *Name = getSymbol(&Alias);
OutStreamer.AddBlankLine();
for (const auto &Alias : M.aliases()) {
MCSymbol *Name = getSymbol(&Alias);
if (Alias.hasExternalLinkage() || !MAI->getWeakRefDirective())
OutStreamer.EmitSymbolAttribute(Name, MCSA_Global);
else if (Alias.hasWeakLinkage() || Alias.hasLinkOnceLinkage())
OutStreamer.EmitSymbolAttribute(Name, MCSA_WeakReference);
else
assert(Alias.hasLocalLinkage() && "Invalid alias linkage");
if (Alias.hasExternalLinkage() || !MAI->getWeakRefDirective())
OutStreamer.EmitSymbolAttribute(Name, MCSA_Global);
else if (Alias.hasWeakLinkage() || Alias.hasLinkOnceLinkage())
OutStreamer.EmitSymbolAttribute(Name, MCSA_WeakReference);
else
assert(Alias.hasLocalLinkage() && "Invalid alias linkage");
EmitVisibility(Name, Alias.getVisibility());
EmitVisibility(Name, Alias.getVisibility());
// Emit the directives as assignments aka .set:
OutStreamer.EmitAssignment(Name,
lowerConstant(Alias.getAliasee(), *this));
}
// Emit the directives as assignments aka .set:
OutStreamer.EmitAssignment(Name, lowerConstant(Alias.getAliasee(), *this));
}
GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
@@ -1163,11 +1160,10 @@ void AsmPrinter::EmitJumpTableInfo() {
// If this jump table was deleted, ignore it.
if (JTBBs.empty()) continue;
// For the EK_LabelDifference32 entry, if the target supports .set, emit a
// .set directive for each unique entry. This reduces the number of
// relocations the assembler will generate for the jump table.
// For the EK_LabelDifference32 entry, if using .set avoids a relocation,
/// emit a .set directive for each unique entry.
if (MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 &&
MAI->hasSetDirective()) {
MAI->doesSetDirectiveSuppressesReloc()) {
SmallPtrSet<const MachineBasicBlock*, 16> EmittedSets;
const TargetLowering *TLI = TM.getSubtargetImpl()->getTargetLowering();
const MCExpr *Base = TLI->getPICJumpTableRelocBaseExpr(MF,JTI,OutContext);
@@ -1240,24 +1236,18 @@ void AsmPrinter::EmitJumpTableEntry(const MachineJumpTableInfo *MJTI,
}
case MachineJumpTableInfo::EK_LabelDifference32: {
// EK_LabelDifference32 - Each entry is the address of the block minus
// the address of the jump table. This is used for PIC jump tables where
// gprel32 is not supported. e.g.:
// Each entry is the address of the block minus the address of the jump
// table. This is used for PIC jump tables where gprel32 is not supported.
// e.g.:
// .word LBB123 - LJTI1_2
// If the .set directive is supported, this is emitted as:
// If the .set directive avoids relocations, this is emitted as:
// .set L4_5_set_123, LBB123 - LJTI1_2
// .word L4_5_set_123
// If we have emitted set directives for the jump table entries, print
// them rather than the entries themselves. If we're emitting PIC, then
// emit the table entries as differences between two text section labels.
if (MAI->hasSetDirective()) {
// If we used .set, reference the .set's symbol.
if (MAI->doesSetDirectiveSuppressesReloc()) {
Value = MCSymbolRefExpr::Create(GetJTSetSymbol(UID, MBB->getNumber()),
OutContext);
break;
}
// Otherwise, use the difference as the jump table entry.
Value = MCSymbolRefExpr::Create(MBB->getSymbol(), OutContext);
const MCExpr *JTI = MCSymbolRefExpr::Create(GetJTISymbol(UID), OutContext);
Value = MCBinaryExpr::CreateSub(Value, JTI, OutContext);
@@ -1441,9 +1431,9 @@ void AsmPrinter::EmitInt32(int Value) const {
OutStreamer.EmitIntValue(Value, 4);
}
/// EmitLabelDifference - Emit something like ".long Hi-Lo" where the size
/// in bytes of the directive is specified by Size and Hi/Lo specify the
/// labels. This implicitly uses .set if it is available.
/// Emit something like ".long Hi-Lo" where the size in bytes of the directive
/// is specified by Size and Hi/Lo specify the labels. This implicitly uses
/// .set if it avoids relocations.
void AsmPrinter::EmitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo,
unsigned Size) const {
// Get the Hi-Lo expression.
@@ -1452,7 +1442,7 @@ void AsmPrinter::EmitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo,
MCSymbolRefExpr::Create(Lo, OutContext),
OutContext);
if (!MAI->hasSetDirective()) {
if (!MAI->doesSetDirectiveSuppressesReloc()) {
OutStreamer.EmitValue(Diff, Size);
return;
}