Fix a bit of confusion about .set and produce more readable assembly.
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.
llvm-svn: 220256
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index dd0d40d..260f39c 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -962,24 +962,21 @@
}
}
- 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 @@
// 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 @@
}
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 @@
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 @@
MCSymbolRefExpr::Create(Lo, OutContext),
OutContext);
- if (!MAI->hasSetDirective()) {
+ if (!MAI->doesSetDirectiveSuppressesReloc()) {
OutStreamer.EmitValue(Diff, Size);
return;
}
diff --git a/llvm/lib/MC/MCAsmInfo.cpp b/llvm/lib/MC/MCAsmInfo.cpp
index ed3d5ed..7574edb 100644
--- a/llvm/lib/MC/MCAsmInfo.cpp
+++ b/llvm/lib/MC/MCAsmInfo.cpp
@@ -64,7 +64,7 @@
GPRel64Directive = nullptr;
GPRel32Directive = nullptr;
GlobalDirective = "\t.globl\t";
- HasSetDirective = true;
+ SetDirectiveSuppressesReloc = false;
HasAggressiveSymbolFolding = true;
COMMDirectiveAlignmentIsInBytes = true;
LCOMMDirectiveAlignmentType = LCOMM::NoAlignment;
diff --git a/llvm/lib/MC/MCAsmInfoDarwin.cpp b/llvm/lib/MC/MCAsmInfoDarwin.cpp
index eaf28dd..96fe216 100644
--- a/llvm/lib/MC/MCAsmInfoDarwin.cpp
+++ b/llvm/lib/MC/MCAsmInfoDarwin.cpp
@@ -60,4 +60,5 @@
DwarfUsesRelocationsAcrossSections = false;
UseIntegratedAssembler = true;
+ SetDirectiveSuppressesReloc = true;
}
diff --git a/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXMCAsmInfo.cpp b/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXMCAsmInfo.cpp
index 295d037..4fd5bdd 100644
--- a/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXMCAsmInfo.cpp
+++ b/llvm/lib/Target/NVPTX/MCTargetDesc/NVPTXMCAsmInfo.cpp
@@ -33,8 +33,6 @@
CommentString = "//";
- HasSetDirective = false;
-
HasSingleParameterDotFile = false;
InlineAsmStart = " inline asm";
diff --git a/llvm/lib/Target/R600/MCTargetDesc/AMDGPUMCAsmInfo.cpp b/llvm/lib/Target/R600/MCTargetDesc/AMDGPUMCAsmInfo.cpp
index f332e4d..fa268e6 100644
--- a/llvm/lib/Target/R600/MCTargetDesc/AMDGPUMCAsmInfo.cpp
+++ b/llvm/lib/Target/R600/MCTargetDesc/AMDGPUMCAsmInfo.cpp
@@ -35,7 +35,6 @@
//===--- Global Variable Emission Directives --------------------------===//
GlobalDirective = ".global";
- HasSetDirective = false;
HasAggressiveSymbolFolding = true;
COMMDirectiveAlignmentIsInBytes = false;
HasDotTypeDotSizeDirective = false;
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 39281c8..fc3662e 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -264,7 +264,8 @@
Expr = MCBinaryExpr::CreateSub(Expr,
MCSymbolRefExpr::Create(MF.getPICBaseSymbol(), Ctx),
Ctx);
- if (MO.isJTI() && MAI.hasSetDirective()) {
+ if (MO.isJTI()) {
+ assert(MAI.doesSetDirectiveSuppressesReloc());
// If .set directive is supported, use it to reduce the number of
// relocations the assembler will generate for differences between
// local labels. This is only safe when the symbols are in the same