[llvm-ir] Add align to the returnAttribute rule (#3657)

Author: NiklasHeneka

llvm-ir/LLVMIR.g4

@@ -114,7 +114,10 @@ gc: 'gc' StringLit;
 prefix: 'prefix' typeConst;
 prologue: 'prologue' typeConst;
 personality: 'personality' typeConst;
-returnAttribute: returnAttr | dereferenceable;
+returnAttribute: 
+    returnAttr 
+    | dereferenceable
+    | align;
 funcBody: '{' basicBlock+ useListOrder* '}';
 basicBlock: LabelIdent? instruction* terminator;
 instruction: // Instructions producing values.
@@ -1433,4 +1436,4 @@ ChecksumKind: 'CSK_' (AsciiLetter | DecimalDigit | '_')*;
 DwarfVirtuality:
 	'DW_VIRTUALITY_' (AsciiLetter | DecimalDigit | '_')*;
 DwarfMacinfo: 'DW_MACINFO_' (AsciiLetter | DecimalDigit | '_')*;
-DwarfOp: 'DW_OP_' (AsciiLetter | DecimalDigit | '_')*;
+DwarfOp: 'DW_OP_' (AsciiLetter | DecimalDigit | '_')*;

llvm-ir/examples/returnAttribute_align.ll

@@ -0,0 +1,4 @@
+define void @main() {
+  %0 = call nonnull align 8 i32 @f()
+  ret void
+}