[AsmParser] make .ascii support spaces as separators

Currently the integrated assembler only allows commas as the separator
between string arguments in .ascii. This patch adds support to using
space as separators and make IAS consistent with GNU assembler.

Link: ClangBuiltLinux/linux#1196

Reviewed By: nickdesaulniers, jrtc27

Differential Revision: https://reviews.llvm.org/D91460

Author: jcai19

llvm/lib/MC/MCParser/AsmParser.cpp

@@ -3008,13 +3008,20 @@ bool AsmParser::parseAngleBracketString(std::string &Data) {
 }
 
 /// parseDirectiveAscii:
-///   ::= ( .ascii | .asciz | .string ) [ "string" ( , "string" )* ]
+//    ::= .ascii [ "string"+ ( , "string"+ )* ]
+///   ::= ( .asciz | .string ) [ "string" ( , "string" )* ]
 bool AsmParser::parseDirectiveAscii(StringRef IDVal, bool ZeroTerminated) {
   auto parseOp = [&]() -> bool {
     std::string Data;
-    if (checkForValidSection() || parseEscapedString(Data))
+    if (checkForValidSection())
       return true;
-    getStreamer().emitBytes(Data);
+    // Only support spaces as separators for .ascii directive for now. See the
+    // discusssion at https://reviews.llvm.org/D91460 for more details
+    do {
+      if (parseEscapedString(Data))
+        return true;
+      getStreamer().emitBytes(Data);
+    } while (!ZeroTerminated && getTok().is(AsmToken::String));
     if (ZeroTerminated)
       getStreamer().emitBytes(StringRef("\0", 1));
     return false;

llvm/test/MC/AsmParser/directive_ascii.s

@@ -48,3 +48,11 @@ TEST6:
 TEST7:
         .ascii "\x64\Xa6B"
         .ascii "\xface\x0Fe"
+
+# CHECK-LABEL: TEST8:
+# CHECK-NEXT: .byte 65
+# CHECK-NEXT: .byte 66
+# CHECK-NEXT: .byte 67
+# CHECK-NEXT: .byte 68
+TEST8:
+        .ascii "A", "B" "C", "D"