Sketch streamer support for .align, .org functionality.

llvm-svn: 74109

llvm/include/llvm/MC/MCStreamer.h

@@ -10,6 +10,8 @@
 #ifndef LLVM_MC_MCSTREAMER_H
 #define LLVM_MC_MCSTREAMER_H
 
+#include "llvm/Support/DataTypes.h"
+
 namespace llvm {
   class MCContext;
   class MCValue;
@@ -53,6 +55,9 @@ namespace llvm {
 
     MCContext &getContext() const { return Context; }
 
+    /// @name Symbol & Section Management
+    /// @{
+
     /// SwitchSection - Set the current section where code is being emitted to
     /// @param Section.
     ///
@@ -98,6 +103,10 @@ namespace llvm {
     virtual void EmitSymbolAttribute(MCSymbol *Symbol,
                                      SymbolAttr Attribute) = 0;
 
+    /// @}
+    /// @name Generating Data
+    /// @{
+
     /// EmitBytes - Emit @param Length bytes starting at @param Data into the
     /// output.
     ///
@@ -116,6 +125,42 @@ namespace llvm {
     /// match a native machine width.
     virtual void EmitValue(const MCValue &Value, unsigned Size) = 0;
 
+    /// EmitValueToAlignment - Emit some number of copies of @param Value until
+    /// the byte alignment @param ByteAlignment is reached.
+    ///
+    /// If the number of bytes need to emit for the alignment is not a multiple
+    /// of @param ValueSize, then the contents of the emitted fill bytes is
+    /// undefined.
+    ///
+    /// This used to implement the .align assembler directive.
+    ///
+    /// @param ByteAlignment - The alignment to reach. This must be a power of
+    /// two.
+    /// @param Value - The value to use when filling bytes.
+    /// @param Size - The size of the integer (in bytes) to emit for @param
+    /// Value. This must match a native machine width.
+    /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If
+    /// the alignment cannot be reached in this many bytes, no bytes are
+    /// emitted.
+    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
+                                      unsigned ValueSize = 1,
+                                      unsigned MaxBytesToEmit = 0) = 0;
+
+    /// EmitValueToOffset - Emit some number of copies of @param Value until the
+    /// byte offset @param Offset is reached.
+    ///
+    /// This is used to implement assembler directives such as .org.
+    ///
+    /// @param Offset - The offset to reach.This may be an expression, but the
+    /// expression must be associated with the current section.
+    /// @param Value - The value to use when filling bytes.
+    // 
+    // FIXME: How are we going to signal failures out of this?
+    virtual void EmitValueToOffset(const MCValue &Offset, 
+                                   unsigned char Value = 0) = 0;
+    
+    /// @}
+
     /// EmitInstruction - Emit the given @param Instruction into the current
     /// section.
     virtual void EmitInstruction(const MCInst &Inst) = 0;

llvm/lib/MC/MCAsmStreamer.cpp

@@ -44,6 +44,13 @@ namespace {
 
     virtual void EmitValue(const MCValue &Value, unsigned Size);
 
+    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
+                                      unsigned ValueSize = 1,
+                                      unsigned MaxBytesToEmit = 0);
+
+    virtual void EmitValueToOffset(const MCValue &Offset, 
+                                   unsigned char Value = 0);
+    
     virtual void EmitInstruction(const MCInst &Inst);
 
     virtual void Finish();
@@ -144,6 +151,36 @@ void MCAsmStreamer::EmitValue(const MCValue &Value, unsigned Size) {
   OS << ' ' << Value << '\n';
 }
 
+void MCAsmStreamer::EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
+                                         unsigned ValueSize,
+                                         unsigned MaxBytesToEmit) {
+  unsigned Pow2 = Log2_32(ByteAlignment);
+  assert((1U << Pow2) == ByteAlignment && "Invalid alignment!");
+
+  switch (ValueSize) {
+  default:
+    assert(0 && "Invalid size for machine code value!");
+  case 8:
+    assert(0 && "Unsupported alignment size!");
+  case 1: OS << ".p2align"; break;
+  case 2: OS << ".p2alignw"; break;
+  case 4: OS << ".p2alignl"; break;
+  }
+
+  OS << ' ' << Pow2;
+
+  OS << ", " << Value;
+  if (MaxBytesToEmit) 
+    OS << ", " << MaxBytesToEmit;
+  OS << '\n';
+}
+
+void MCAsmStreamer::EmitValueToOffset(const MCValue &Offset, 
+                                      unsigned char Value) {
+  // FIXME: Verify that Offset is associated with the current section.
+  OS << ".org " << Offset << ", " << (unsigned) Value << '\n';
+}
+
 void MCAsmStreamer::EmitInstruction(const MCInst &Inst) {
   assert(CurSection && "Cannot emit contents before setting section!");
   // FIXME: Implement.

llvm/unittests/MC/AsmStreamerTest.cpp

@@ -72,4 +72,32 @@ b:\n\
 ");
 }
 
+TEST(AsmStreamer, Align) {
+  StringAsmStreamer S;
+  MCSection *Sec0 = S.getContext().GetSection("foo");
+  S.getStreamer().SwitchSection(Sec0);
+  S.getStreamer().EmitValueToAlignment(4);
+  S.getStreamer().EmitValueToAlignment(4, /*Value=*/12, /*ValueSize=*/2);
+  S.getStreamer().EmitValueToAlignment(8, /*Value=*/12, /*ValueSize=*/4, 
+                                       /*MaxBytesToEmit=*/24);
+  EXPECT_EQ(S.getString(), ".section foo\n\
+.p2align 2, 0\n\
+.p2alignw 2, 12\n\
+.p2alignl 3, 12, 24\n\
+");
+}
+
+TEST(AsmStreamer, Org) {
+  StringAsmStreamer S;
+  MCSection *Sec0 = S.getContext().GetSection("foo");
+  S.getStreamer().SwitchSection(Sec0);
+  MCSymbol *A = S.getContext().CreateSymbol("a");
+  S.getStreamer().EmitLabel(A);
+  S.getStreamer().EmitValueToOffset(MCValue::get(A, 0, 4), 32);
+  EXPECT_EQ(S.getString(), ".section foo\n\
+a:\n\
+.org a + 4, 32\n\
+");
+}
+
 }