diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -5734,13 +5734,17 @@
   }
 
   // If we have a '#', it's an immediate offset, else assume it's a register
-  // offset. Be friendly and also accept a plain integer (without a leading
-  // hash) for gas compatibility.
+  // offset. Be friendly and also accept a plain integer or expression (without
+  // a leading hash) for gas compatibility.
   if (Parser.getTok().is(AsmToken::Hash) ||
       Parser.getTok().is(AsmToken::Dollar) ||
+      Parser.getTok().is(AsmToken::LParen) ||
       Parser.getTok().is(AsmToken::Integer)) {
-    if (Parser.getTok().isNot(AsmToken::Integer))
-      Parser.Lex(); // Eat '#' or '$'.
+    bool StartsWithParen = false;
+    if (Parser.getTok().isNot(AsmToken::Integer)) {
+      StartsWithParen = Parser.getTok().is(AsmToken::LParen);
+      Parser.Lex(); // Eat '#' or '$' or '('
+    }
     E = Parser.getTok().getLoc();
 
     bool isNegative = getParser().getTok().is(AsmToken::Minus);
@@ -5762,6 +5766,10 @@
       CE = MCConstantExpr::create(std::numeric_limits<int32_t>::min(),
                                   getContext());
 
+    // Check if the offset is surrounded by parentheses
+    if (StartsWithParen && Parser.getTok().isNot(AsmToken::RParen))
+      return Error(Parser.getTok().getLoc(), "')' expected");
+
     // Now we should have the closing ']'
     if (Parser.getTok().isNot(AsmToken::RBrac))
       return Error(Parser.getTok().getLoc(), "']' expected");
diff --git a/llvm/test/MC/ARM/gas-compl.s b/llvm/test/MC/ARM/gas-compl.s
new file mode 100644
--- /dev/null
+++ b/llvm/test/MC/ARM/gas-compl.s
@@ -0,0 +1,8 @@
+@ RUN: llvm-mc -triple=arm < %s | FileCheck %s
+
+@ CHECK: ldr	r12, [sp, #15]
+.syntax unified
+  ldr r12, [sp, #(15)]
+@ CHECK: ldr	r12, [sp, #40]
+.syntax unified
+  ldr r12, [sp, #(15+5*5)]