Restore r125595 (reverted in r126336) with modifications:

Introduce a variable in the AsmParserExtension whether [] is valid in an
expression. If it is true, parse them like (). Enable this for ELF only.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126443 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCParser/MCAsmParserExtension.h

@@ -38,6 +38,8 @@ protected:
     return (Obj->*Handler)(Directive, DirectiveLoc);
   }
 
+  bool BracketExpressionsSupported;
+
 public:
   virtual ~MCAsmParserExtension();
 
@@ -68,6 +70,8 @@ public:
 
   const AsmToken &getTok() { return getParser().getTok(); }
 
+  bool HasBracketExpressions() const { return BracketExpressionsSupported; }
+
   /// @}
 };
 

lib/MC/MCParser/AsmParser.cpp

@@ -173,6 +173,7 @@ private:
   bool ParsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc);
   bool ParseBinOpRHS(unsigned Precedence, const MCExpr *&Res, SMLoc &EndLoc);
   bool ParseParenExpr(const MCExpr *&Res, SMLoc &EndLoc);
+  bool ParseBracketExpr(const MCExpr *&Res, SMLoc &EndLoc);
 
   /// ParseIdentifier - Parse an identifier or string (as a quoted identifier)
   /// and set \arg Res to the identifier contents.
@@ -492,6 +493,20 @@ bool AsmParser::ParseParenExpr(const MCExpr *&Res, SMLoc &EndLoc) {
   return false;
 }
 
+/// ParseBracketExpr - Parse a bracket expression and return it.
+/// NOTE: This assumes the leading '[' has already been consumed.
+///
+/// bracketexpr ::= expr]
+///
+bool AsmParser::ParseBracketExpr(const MCExpr *&Res, SMLoc &EndLoc) {
+  if (ParseExpression(Res)) return true;
+  if (Lexer.isNot(AsmToken::RBrac))
+    return TokError("expected ']' in brackets expression");
+  EndLoc = Lexer.getLoc();
+  Lex();
+  return false;
+}
+
 /// ParsePrimaryExpr - Parse a primary expression and return it.
 ///  primaryexpr ::= (parenexpr
 ///  primaryexpr ::= symbol
@@ -587,6 +602,11 @@ bool AsmParser::ParsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
   case AsmToken::LParen:
     Lex(); // Eat the '('.
     return ParseParenExpr(Res, EndLoc);
+  case AsmToken::LBrac:
+    if (!PlatformParser->HasBracketExpressions())
+      return TokError("brackets expression not supported on this target");
+    Lex(); // Eat the '['.
+    return ParseBracketExpr(Res, EndLoc);
   case AsmToken::Minus:
     Lex(); // Eat the operator.
     if (ParsePrimaryExpr(Res, EndLoc))

lib/MC/MCParser/ELFAsmParser.cpp

@@ -33,7 +33,9 @@ class ELFAsmParser : public MCAsmParserExtension {
   bool SeenIdent;
 
 public:
-  ELFAsmParser() : SeenIdent(false) {}
+  ELFAsmParser() : SeenIdent(false) {
+    BracketExpressionsSupported = true;
+  }
 
   virtual void Initialize(MCAsmParser &Parser) {
     // Call the base implementation.

lib/MC/MCParser/MCAsmParserExtension.cpp

@@ -10,7 +10,8 @@
 #include "llvm/MC/MCParser/MCAsmParserExtension.h"
 using namespace llvm;
 
-MCAsmParserExtension::MCAsmParserExtension() {
+MCAsmParserExtension::MCAsmParserExtension() :
+  BracketExpressionsSupported(false) {
 }
 
 MCAsmParserExtension::~MCAsmParserExtension() {

test/MC/ARM/bracket-darwin.s

@@ -0,0 +1,5 @@
+// RUN: not llvm-mc -triple arm-apple-darwin %s 2> %t
+// RUN: FileCheck -input-file %t %s
+
+// CHECK: error: brackets expression not supported on this target
+.byte	[4-3]

test/MC/ELF/bracket-exprs.s

@@ -0,0 +1,16 @@
+// RUN: llvm-mc -triple i386-unknown-unknown %s | FileCheck %s
+// RUN: llvm-mc -triple arm-unknown-linux %s | FileCheck %s
+
+// CHECK: .byte 1
+.if [~0 >> 1] == -1
+.byte 1
+.else
+.byte 2
+.endif
+
+// CHECK: .byte 3
+.if 4 * [4 + (3 + [2 * 2] + 1)] == 48
+.byte 3
+.else
+.byte 4
+.endif

test/MC/ELF/bracket.s

@@ -0,0 +1,8 @@
+// RUN: not llvm-mc -triple i386-unknown-unknown %s 2> %t1 > %t2
+// RUN: FileCheck < %t1 %s
+
+// CHECK: error: expected ']' in brackets expression
+.size	x, [.-x)
+
+// CHECK: error: expected ')' in parentheses expression
+.size	y, (.-y]