[llvm] r191368 - MC: Add support for treating $ as a reference to the PC

[David Majnemer]

Author: majnemer
Date: Wed Sep 25 05:47:21 2013
New Revision: 191368

URL: http://llvm.org/viewvc/llvm-project?rev=191368&view=rev
Log:
MC: Add support for treating $ as a reference to the PC

The binutils assembler supports a mode called DOLLAR_DOT which treats
the dollar sign token as a reference to the current program counter if
the dollar sign doesn't precede a constant or identifier.

This commit adds a new MCAsmInfo flag stating whether or not a given
target supports this interpretation of the dollar sign token; by
default, this flag is not enabled.

Further, enable this flag for PPC. The system assembler for AIX and
binutils both support using the dollar sign in this manner.

This fixes PR17353.

Modified:
    llvm/trunk/include/llvm/MC/MCAsmInfo.h
    llvm/trunk/lib/MC/MCAsmInfo.cpp
    llvm/trunk/lib/MC/MCParser/AsmParser.cpp
    llvm/trunk/lib/Target/PowerPC/MCTargetDesc/PPCMCAsmInfo.cpp
    llvm/trunk/test/MC/PowerPC/ppc64-operands.s

Modified: llvm/trunk/include/llvm/MC/MCAsmInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCAsmInfo.h?rev=191368&r1=191367&r2=191368&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCAsmInfo.h (original)
+++ llvm/trunk/include/llvm/MC/MCAsmInfo.h Wed Sep 25 05:47:21 2013
@@ -93,6 +93,10 @@ namespace llvm {
     /// this value.  Factored out in .debug_frame and .debug_line.
     unsigned MinInstAlignment;                  // Defaults to 1.
 
+    /// DollarIsPC - The '$' token, when not referencing an identifier or
+    /// constant, refers to the current PC.
+    bool DollarIsPC;                         // Defaults to false.
+
     /// SeparatorString - This string, if specified, is used to separate
     /// instructions from each other when on the same line.
     const char *SeparatorString;             // Defaults to ';'
@@ -421,6 +425,9 @@ namespace llvm {
     unsigned getMinInstAlignment() const {
       return MinInstAlignment;
     }
+    bool getDollarIsPC() const {
+      return DollarIsPC;
+    }
     const char *getSeparatorString() const {
       return SeparatorString;
     }

Modified: llvm/trunk/lib/MC/MCAsmInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCAsmInfo.cpp?rev=191368&r1=191367&r2=191368&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCAsmInfo.cpp (original)
+++ llvm/trunk/lib/MC/MCAsmInfo.cpp Wed Sep 25 05:47:21 2013
@@ -35,6 +35,7 @@ MCAsmInfo::MCAsmInfo() {
   LinkerRequiresNonEmptyDwarfLines = false;
   MaxInstLength = 4;
   MinInstAlignment = 1;
+  DollarIsPC = false;
   SeparatorString = ";";
   CommentColumn = 40;
   CommentString = "#";

Modified: llvm/trunk/lib/MC/MCParser/AsmParser.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCParser/AsmParser.cpp?rev=191368&r1=191367&r2=191368&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCParser/AsmParser.cpp (original)
+++ llvm/trunk/lib/MC/MCParser/AsmParser.cpp Wed Sep 25 05:47:21 2013
@@ -772,9 +772,19 @@ bool AsmParser::parsePrimaryExpr(const M
   case AsmToken::Identifier: {
     StringRef Identifier;
     if (parseIdentifier(Identifier)) {
-      if (FirstTokenKind == AsmToken::Dollar)
-        return Error(FirstTokenLoc, "invalid token in expression");
-      return true;
+      if (FirstTokenKind == AsmToken::Dollar) {
+        if (Lexer.getMAI().getDollarIsPC()) {
+          // This is a '$' reference, which references the current PC.  Emit a
+          // temporary label to the streamer and refer to it.
+          MCSymbol *Sym = Ctx.CreateTempSymbol();
+          Out.EmitLabel(Sym);
+          Res = MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_None, getContext());
+          EndLoc = FirstTokenLoc;
+          return false;
+        } else
+          return Error(FirstTokenLoc, "invalid token in expression");
+        return true;
+      }
     }
 
     EndLoc = SMLoc::getFromPointer(Identifier.end());

Modified: llvm/trunk/lib/Target/PowerPC/MCTargetDesc/PPCMCAsmInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/MCTargetDesc/PPCMCAsmInfo.cpp?rev=191368&r1=191367&r2=191368&view=diff
==============================================================================
--- llvm/trunk/lib/Target/PowerPC/MCTargetDesc/PPCMCAsmInfo.cpp (original)
+++ llvm/trunk/lib/Target/PowerPC/MCTargetDesc/PPCMCAsmInfo.cpp Wed Sep 25 05:47:21 2013
@@ -54,6 +54,8 @@ PPCLinuxMCAsmInfo::PPCLinuxMCAsmInfo(boo
   // Debug Information
   SupportsDebugInformation = true;
 
+  DollarIsPC = true;
+
   // Set up DWARF directives
   HasLEB128 = true;  // Target asm supports leb128 directives (little-endian)
   MinInstAlignment = 4;

Modified: llvm/trunk/test/MC/PowerPC/ppc64-operands.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/PowerPC/ppc64-operands.s?rev=191368&r1=191367&r2=191368&view=diff
==============================================================================
--- llvm/trunk/test/MC/PowerPC/ppc64-operands.s (original)
+++ llvm/trunk/test/MC/PowerPC/ppc64-operands.s Wed Sep 25 05:47:21 2013
@@ -108,3 +108,8 @@
 # CHECK: beqa 0, 1024                    # encoding: [0x41,0x82,0x04,0x02]
          beqa 1024
 
+# CHECK:                                 # encoding: [0x42,0x9f,A,0bAAAAAA01]
+         bcl 20, 31, $+4
+
+# CHECK:                                 # encoding: [0x42,0x00,A,0bAAAAAA00]
+         bdnz $-8