Index: llvm/trunk/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
===================================================================
--- llvm/trunk/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
+++ llvm/trunk/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
@@ -349,6 +349,20 @@
     Parser.Lex();
   }
 
+  bool parseSingleFloat(bool IsNegative, OperandVector &Operands) {
+    auto &Flt = Lexer.getTok();
+    double Val;
+    if (Flt.getString().getAsDouble(Val, false))
+      return error("Cannot parse real: ", Flt);
+    if (IsNegative)
+      Val = -Val;
+    Operands.push_back(make_unique<WebAssemblyOperand>(
+        WebAssemblyOperand::Float, Flt.getLoc(), Flt.getEndLoc(),
+        WebAssemblyOperand::FltOp{Val}));
+    Parser.Lex();
+    return false;
+  }
+
   bool checkForP2AlignIfLoadStore(OperandVector &Operands, StringRef InstName) {
     // FIXME: there is probably a cleaner way to do this.
     auto IsLoadStore = InstName.find(".load") != StringRef::npos ||
@@ -486,11 +500,17 @@
       }
       case AsmToken::Minus:
         Parser.Lex();
-        if (Lexer.isNot(AsmToken::Integer))
-          return error("Expected integer instead got: ", Lexer.getTok());
-        parseSingleInteger(true, Operands);
-        if (checkForP2AlignIfLoadStore(Operands, Name))
-          return true;
+        if (Lexer.is(AsmToken::Integer)) {
+          parseSingleInteger(true, Operands);
+          if (checkForP2AlignIfLoadStore(Operands, Name))
+            return true;
+        } else if(Lexer.is(AsmToken::Real)) {
+          if (parseSingleFloat(true, Operands))
+            return true;
+        } else {
+          return error("Expected numeric constant instead got: ",
+                       Lexer.getTok());
+        }
         break;
       case AsmToken::Integer:
         parseSingleInteger(false, Operands);
@@ -498,13 +518,8 @@
           return true;
         break;
       case AsmToken::Real: {
-        double Val;
-        if (Tok.getString().getAsDouble(Val, false))
-          return error("Cannot parse real: ", Tok);
-        Operands.push_back(make_unique<WebAssemblyOperand>(
-            WebAssemblyOperand::Float, Tok.getLoc(), Tok.getEndLoc(),
-            WebAssemblyOperand::FltOp{Val}));
-        Parser.Lex();
+        if (parseSingleFloat(false, Operands))
+          return true;
         break;
       }
       case AsmToken::LCurly: {
Index: llvm/trunk/test/MC/WebAssembly/basic-assembly.s
===================================================================
--- llvm/trunk/test/MC/WebAssembly/basic-assembly.s
+++ llvm/trunk/test/MC/WebAssembly/basic-assembly.s
@@ -13,6 +13,7 @@
     # Immediates:
     i32.const   -1
     f64.const   0x1.999999999999ap1
+    f32.const   -1.0
     v128.const  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
     v128.const  0, 1, 2, 3, 4, 5, 6, 7
     # Indirect addressing:
@@ -112,6 +113,7 @@
 # CHECK-NEXT:      local.set   2
 # CHECK-NEXT:      i32.const   -1
 # CHECK-NEXT:      f64.const   0x1.999999999999ap1
+# CHECK-NEXT:      f32.const   -0x1p0
 # CHECK-NEXT:      v128.const  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
 # CHECK-NEXT:      v128.const  0, 1, 2, 3, 4, 5, 6, 7
 # CHECK-NEXT:      local.get   0