3 files changed, 38 insertions, 15 deletions

diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index 4e8dcf61491..927c1889c88 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -910,7 +910,7 @@ void MCAsmStreamer::EmitULEB128Value(const MCExpr *Value) {
     EmitULEB128IntValue(IntValue);
     return;
   }
-  OS << ".uleb128 ";
+  OS << "\t.uleb128 ";
   Value->print(OS, MAI);
   EmitEOL();
 }
@@ -921,7 +921,7 @@ void MCAsmStreamer::EmitSLEB128Value(const MCExpr *Value) {
     EmitSLEB128IntValue(IntValue);
     return;
   }
-  OS << ".sleb128 ";
+  OS << "\t.sleb128 ";
   Value->print(OS, MAI);
   EmitEOL();
 }
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index 230c02188a6..9c69a5a962d 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -51,17 +51,34 @@ void MCObjectStreamer::flushPendingLabels(MCFragment *F, uint64_t FOffset) {
   PendingLabels.clear();
 }
 
+// As a compile-time optimization, avoid allocating and evaluating an MCExpr
+// tree for (Hi - Lo) when Hi and Lo are offsets into the same fragment.
+static Optional<uint64_t> absoluteSymbolDiff(const MCSymbol *Hi,
+                                             const MCSymbol *Lo) {
+  if (!Hi->getFragment() || Hi->getFragment() != Lo->getFragment() ||
+      Hi->isVariable() || Lo->isVariable())
+    return None;
+
+  return Hi->getOffset() - Lo->getOffset();
+}
+
 void MCObjectStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi,
                                               const MCSymbol *Lo,
                                               unsigned Size) {
-  // If not assigned to the same (valid) fragment, fallback.
-  if (!Hi->getFragment() || Hi->getFragment() != Lo->getFragment() ||
-      Hi->isVariable() || Lo->isVariable()) {
-    MCStreamer::emitAbsoluteSymbolDiff(Hi, Lo, Size);
+  if (Optional<uint64_t> Diff = absoluteSymbolDiff(Hi, Lo)) {
+    EmitIntValue(*Diff, Size);
     return;
   }
+  MCStreamer::emitAbsoluteSymbolDiff(Hi, Lo, Size);
+}
 
-  EmitIntValue(Hi->getOffset() - Lo->getOffset(), Size);
+void MCObjectStreamer::emitAbsoluteSymbolDiffAsULEB128(const MCSymbol *Hi,
+                                                       const MCSymbol *Lo) {
+  if (Optional<uint64_t> Diff = absoluteSymbolDiff(Hi, Lo)) {
+    EmitULEB128IntValue(*Diff);
+    return;
+  }
+  MCStreamer::emitAbsoluteSymbolDiffAsULEB128(Hi, Lo);
 }
 
 void MCObjectStreamer::reset() {
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index 9dcd1e9101c..bc9c93f144e 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -120,20 +120,16 @@ void MCStreamer::EmitIntValue(uint64_t Value, unsigned Size) {
   EmitBytes(StringRef(buf, Size));
 }
 
-/// EmitULEB128Value - Special case of EmitULEB128Value that avoids the
+/// EmitULEB128IntValue - Special case of EmitULEB128Value that avoids the
 /// client having to pass in a MCExpr for constant integers.
-void MCStreamer::EmitPaddedULEB128IntValue(uint64_t Value, unsigned PadTo) {
+void MCStreamer::EmitULEB128IntValue(uint64_t Value) {
   SmallString<128> Tmp;
   raw_svector_ostream OSE(Tmp);
-  encodeULEB128(Value, OSE, PadTo);
+  encodeULEB128(Value, OSE);
   EmitBytes(OSE.str());
 }
 
-void MCStreamer::EmitULEB128IntValue(uint64_t Value) {
-  EmitPaddedULEB128IntValue(Value, 0);
-}
-
-/// EmitSLEB128Value - Special case of EmitSLEB128Value that avoids the
+/// EmitSLEB128IntValue - Special case of EmitSLEB128Value that avoids the
 /// client having to pass in a MCExpr for constant integers.
 void MCStreamer::EmitSLEB128IntValue(int64_t Value) {
   SmallString<128> Tmp;
@@ -902,6 +898,16 @@ void MCStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi, const MCSymbol *Lo,
   EmitSymbolValue(SetLabel, Size);
 }
 
+void MCStreamer::emitAbsoluteSymbolDiffAsULEB128(const MCSymbol *Hi,
+                                                 const MCSymbol *Lo) {
+  // Get the Hi-Lo expression.
+  const MCExpr *Diff =
+      MCBinaryExpr::createSub(MCSymbolRefExpr::create(Hi, Context),
+                              MCSymbolRefExpr::create(Lo, Context), Context);
+
+  EmitULEB128Value(Diff);
+}
+
 void MCStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {}
 void MCStreamer::EmitThumbFunc(MCSymbol *Func) {}
 void MCStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {}