LLParser: Accept align(N) as new syntax for parameter attribute

Every other value parameter attribute uses parentheses, so accept this
as the preferred modern syntax. Updating everything to use the new
syntax is left for a future change.

docs/LangRef.rst

@@ -1130,7 +1130,7 @@ Currently, only the following parameter attributes are defined:
 
 .. _attr_align:
 
-``align <n>``
+``align <n>`` or ``align(<n>)``
     This indicates that the pointer value may be assumed by the optimizer to
     have the specified alignment.  If the pointer value does not have the
     specified alignment, behavior is undefined.

lib/AsmParser/LLParser.cpp

@@ -1641,7 +1641,7 @@ bool LLParser::ParseOptionalParamAttrs(AttrBuilder &B) {
     }
     case lltok::kw_align: {
       MaybeAlign Alignment;
-      if (ParseOptionalAlignment(Alignment))
+      if (ParseOptionalAlignment(Alignment, true))
         return true;
       B.addAlignmentAttr(Alignment);
       continue;
@@ -2127,14 +2127,26 @@ bool LLParser::ParseOptionalFunctionMetadata(Function &F) {
 /// ParseOptionalAlignment
 ///   ::= /* empty */
 ///   ::= 'align' 4
-bool LLParser::ParseOptionalAlignment(MaybeAlign &Alignment) {
+bool LLParser::ParseOptionalAlignment(MaybeAlign &Alignment, bool AllowParens) {
   Alignment = None;
   if (!EatIfPresent(lltok::kw_align))
     return false;
   LocTy AlignLoc = Lex.getLoc();
   uint32_t Value = 0;
+
+  LocTy ParenLoc = Lex.getLoc();
+  bool HaveParens = false;
+  if (AllowParens) {
+    if (EatIfPresent(lltok::lparen))
+      HaveParens = true;
+  }
+
   if (ParseUInt32(Value))
     return true;
+
+  if (HaveParens && !EatIfPresent(lltok::rparen))
+    return Error(ParenLoc, "expected ')'");
+
   if (!isPowerOf2_32(Value))
     return Error(AlignLoc, "alignment is not a power of two");
   if (Value > Value::MaximumAlignment)

lib/AsmParser/LLParser.h

@@ -272,7 +272,8 @@ namespace llvm {
     void ParseOptionalVisibility(unsigned &Res);
     void ParseOptionalDLLStorageClass(unsigned &Res);
     bool ParseOptionalCallingConv(unsigned &CC);
-    bool ParseOptionalAlignment(MaybeAlign &Alignment);
+    bool ParseOptionalAlignment(MaybeAlign &Alignment,
+                                bool AllowParens = false);
     bool ParseOptionalDerefAttrBytes(lltok::Kind AttrKind, uint64_t &Bytes);
     bool ParseScopeAndOrdering(bool isAtomic, SyncScope::ID &SSID,
                                AtomicOrdering &Ordering);

test/Assembler/align-param-attr-error0.ll

@@ -0,0 +1,7 @@
+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+; Test parse errors when using form of align attribute with parentheses
+
+; CHECK:  <stdin>:[[@LINE+1]]:38: error: expected ')'
+define void @missing_rparen(i8* align(4 %ptr) {
+  ret void
+}

test/Assembler/align-param-attr-error1.ll

@@ -0,0 +1,7 @@
+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+; Test parse errors when using form of align attribute with parentheses
+
+; CHECK:  <stdin>:[[@LINE+1]]:42: error: expected '{' in function body
+define void @missing_Lparen(i8* align 4) %ptr) {
+  ret void
+}

test/Assembler/align-param-attr-error2.ll

@@ -0,0 +1,7 @@
+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+; Test parse errors when using form of align attribute with parentheses
+
+; CHECK:  <stdin>:[[@LINE+1]]:39: error: expected integer
+define void @missing_value(i8* align () %ptr) {
+  ret void
+}

test/Assembler/align-param-attr-format.ll

@@ -0,0 +1,13 @@
+; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
+
+; Test that align(N) is accepted as an alternative syntax to align N
+
+; CHECK: define void @param_align4(i8* align 4 %ptr) {
+define void @param_align4(i8* align(4) %ptr) {
+  ret void
+}
+
+; CHECK: define void @param_align128(i8* align 128 %0) {
+define void @param_align128(i8* align(128)) {
+  ret void
+}