diff --git a/lib/Parser/Lexer.cpp b/lib/Parser/Lexer.cpp
index ffc12c8..91596d3 100644
--- a/lib/Parser/Lexer.cpp
+++ b/lib/Parser/Lexer.cpp
@@ -100,7 +100,11 @@
 
     return formToken(Token::question, tokStart);
 
-  case ';': return lexComment();
+  case '/':
+    if (*curPtr == '/')
+      return lexComment();
+    return emitError(tokStart, "unexpected character");
+
   case '@': return lexAtIdentifier(tokStart);
   case '#':
     LLVM_FALLTHROUGH;
@@ -119,6 +123,10 @@
 ///   TODO: add a regex for comments here and to the spec.
 ///
 Token Lexer::lexComment() {
+  // Advance over the second '/' in a '//' comment.
+  assert(*curPtr == '/');
+  ++curPtr;
+
   while (true) {
     switch (*curPtr++) {
     case '\n':
diff --git a/test/IR/check-help-output.mlir b/test/IR/check-help-output.mlir
index 617ae78..bf0ee49 100644
--- a/test/IR/check-help-output.mlir
+++ b/test/IR/check-help-output.mlir
@@ -1,7 +1,7 @@
-; TODO(andydavis) Resolve relative path issue w.r.t invoking mlir-opt in RUN
-; statements (perhaps through using lit config substitutions).
-;
-; RUN: %S/../../mlir-opt --help | FileCheck %s
-;
-; CHECK: OVERVIEW: MLIR modular optimizer driver
+// TODO(andydavis) Resolve relative path issue w.r.t invoking mlir-opt in RUN
+// statements (perhaps through using lit config substitutions).
+//
+// RUN: %S/../../mlir-opt --help | FileCheck %s
+//
+// CHECK: OVERVIEW: MLIR modular optimizer driver
 
diff --git a/test/IR/parser-affine-map-negative.mlir b/test/IR/parser-affine-map-negative.mlir
index a795b3b..4ef4615 100644
--- a/test/IR/parser-affine-map-negative.mlir
+++ b/test/IR/parser-affine-map-negative.mlir
@@ -1,122 +1,122 @@
-;
-; RUN: %S/../../mlir-opt %s -o - -check-parser-errors
+//
+// RUN: %S/../../mlir-opt %s -o - -check-parser-errors
 
-; Check different error cases.
-; -----
-#hello_world = (i, j) -> ((), j) ; expected-error {{no expression inside parentheses}}
+// Check different error cases.
+// -----
+#hello_world = (i, j) -> ((), j) // expected-error {{no expression inside parentheses}}
 
-; -----
-#hello_world = (i, j) -> (->, j) ; expected-error {{expected affine expression}}
+// -----
+#hello_world = (i, j) -> (->, j) // expected-error {{expected affine expression}}
 
-; -----
-#hello_world = (i, j) -> (:) ; expected-error {{expected affine expression}}
+// -----
+#hello_world = (i, j) -> (:) // expected-error {{expected affine expression}}
 
-; -----
-#hello_world = (i, j) -> (, j) ; expected-error {{expected affine expression}}
+// -----
+#hello_world = (i, j) -> (, j) // expected-error {{expected affine expression}}
 
-; -----
-#hello_world (i, j) [s0] -> (i, j) ; expected-error {{expected '=' in affine map outlined definition}}
+// -----
+#hello_world (i, j) [s0] -> (i, j) // expected-error {{expected '=' in affine map outlined definition}}
 
-; -----
-#hello_world = (i, j) [s0] -> (2*i*, 3*j*i*2 + 5) ; expected-error {{missing right operand of binary op}}
+// -----
+#hello_world = (i, j) [s0] -> (2*i*, 3*j*i*2 + 5) // expected-error {{missing right operand of binary op}}
 
-; -----
-#hello_world = (i, j) [s0] -> (i+, i+j+2 + 5) ; expected-error {{missing right operand of binary op}}
+// -----
+#hello_world = (i, j) [s0] -> (i+, i+j+2 + 5) // expected-error {{missing right operand of binary op}}
 
-; -----
-#hello_world = (i, j) [s0] -> ((s0 + i, j) ; expected-error {{expected ')'}}
+// -----
+#hello_world = (i, j) [s0] -> ((s0 + i, j) // expected-error {{expected ')'}}
 
-; -----
-#hello_world = (i, j) [s0] -> (((s0 + (i + j) + 5), j) ; expected-error {{expected ')'}}
+// -----
+#hello_world = (i, j) [s0] -> (((s0 + (i + j) + 5), j) // expected-error {{expected ')'}}
 
-; -----
-#hello_world = (i, j) [s0] -> i + s0, j) ; expected-error {{expected '(' at start of affine map range}}
+// -----
+#hello_world = (i, j) [s0] -> i + s0, j) // expected-error {{expected '(' at start of affine map range}}
 
-; -----
-#hello_world = (i, j) [s0] -> (x) ; expected-error {{use of undeclared identifier}}
+// -----
+#hello_world = (i, j) [s0] -> (x) // expected-error {{use of undeclared identifier}}
 
-; -----
-#hello_world = (i, j, i) [s0] -> (i) ; expected-error {{dimensional identifier name reused}}
+// -----
+#hello_world = (i, j, i) [s0] -> (i) // expected-error {{dimensional identifier name reused}}
 
-; -----
-#hello_world = (i, j) [s0, s1, s0] -> (i) ; expected-error {{symbolic identifier name reused}}
+// -----
+#hello_world = (i, j) [s0, s1, s0] -> (i) // expected-error {{symbolic identifier name reused}}
 
-; -----
-#hello_world = (i, j) [i, s0] -> (j) ; expected-error {{dimensional identifier name reused}}
+// -----
+#hello_world = (i, j) [i, s0] -> (j) // expected-error {{dimensional identifier name reused}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> () ; expected-error {{expected list element}}
+// -----
+#hello_world = (i, j) [s0, s1] -> () // expected-error {{expected list element}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (+i, j) ; expected-error {{missing left operand of binary op}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (+i, j) // expected-error {{missing left operand of binary op}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (i, *j) ; expected-error {{missing left operand of binary op}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (i, *j) // expected-error {{missing left operand of binary op}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (floordiv i 2, j) ; expected-error {{missing left operand of binary op}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (floordiv i 2, j) // expected-error {{missing left operand of binary op}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (ceildiv i 2, j) ; expected-error {{missing left operand of binary op}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (ceildiv i 2, j) // expected-error {{missing left operand of binary op}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (mod i 2, j) ; expected-error {{missing left operand of binary op}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (mod i 2, j) // expected-error {{missing left operand of binary op}}
 
-; -----
+// -----
 #hello_world = (i, j) [s0, s1] -> (-(), j)
-; expected-error@-1 {{no expression inside parentheses}}
-; expected-error@-2 {{missing operand of negation}}
+// expected-error@-1 {{no expression inside parentheses}}
+// expected-error@-2 {{missing operand of negation}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (i, *j+5) ; expected-error {{missing left operand of binary op}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (i, *j+5) // expected-error {{missing left operand of binary op}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (i, floordiv j+5) ; expected-error {{missing left operand of binary op}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (i, floordiv j+5) // expected-error {{missing left operand of binary op}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (i, ceildiv j+5) ; expected-error {{missing left operand of binary op}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (i, ceildiv j+5) // expected-error {{missing left operand of binary op}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (i, mod j+5) ; expected-error {{missing left operand of binary op}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (i, mod j+5) // expected-error {{missing left operand of binary op}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (i*j, j) ; expected-error {{non-affine expression: at least one of the multiply operands has to be either a constant or symbolic}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (i*j, j) // expected-error {{non-affine expression: at least one of the multiply operands has to be either a constant or symbolic}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (i, j + j ceildiv 128 mod 16 * i - 4) ; expected-error {{non-affine expression: at least one of the multiply operands has to be either a constant or symbolic}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (i, j + j ceildiv 128 mod 16 * i - 4) // expected-error {{non-affine expression: at least one of the multiply operands has to be either a constant or symbolic}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (i, j floordiv i) ; expected-error {{non-affine expression: right operand of floordiv has to be either a constant or symbolic}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (i, j floordiv i) // expected-error {{non-affine expression: right operand of floordiv has to be either a constant or symbolic}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (i, i*2 ceildiv j*5) ; expected-error {{non-affine expression: right operand of ceildiv has to be either a constant or symbolic}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (i, i*2 ceildiv j*5) // expected-error {{non-affine expression: right operand of ceildiv has to be either a constant or symbolic}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (i, i mod (2+i)) ; expected-error {{non-affine expression: right operand of mod has to be either a constant or symbolic}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (i, i mod (2+i)) // expected-error {{non-affine expression: right operand of mod has to be either a constant or symbolic}}
 
-; -----
-#hello_world = (i, j) [s0, s1] -> (-1*i j, j) ; expected-error {{expected ',' or ')'}}
+// -----
+#hello_world = (i, j) [s0, s1] -> (-1*i j, j) // expected-error {{expected ',' or ')'}}
 
-; -----
-#hello_world = (i, j) -> (i, 3*d0 + ) ; expected-error {{use of undeclared identifier}}
+// -----
+#hello_world = (i, j) -> (i, 3*d0 + ) // expected-error {{use of undeclared identifier}}
 
-; -----
-#hello_world = (i, j) -> (i, j) size (10, x) ; expected-error {{use of undeclared identifier}}
+// -----
+#hello_world = (i, j) -> (i, j) size (10, x) // expected-error {{use of undeclared identifier}}
 
-; -----
-#hello_world = (i, j) [M] -> (i, j) size (10, j) ; expected-error {{identifier used is not a symbolic identifier}}
+// -----
+#hello_world = (i, j) [M] -> (i, j) size (10, j) // expected-error {{identifier used is not a symbolic identifier}}
 
-; -----
-#hello_world = (i, j) [M] -> (i, j) size (10, M+i) ; expected-error {{identifier used is not a symbolic identifier}}
+// -----
+#hello_world = (i, j) [M] -> (i, j) size (10, M+i) // expected-error {{identifier used is not a symbolic identifier}}
 
-; -----
-#hello_world = (i, j) -> (i, j) size (10) ; expected-error {{fewer range sizes than range expressions}}
+// -----
+#hello_world = (i, j) -> (i, j) size (10) // expected-error {{fewer range sizes than range expressions}}
 
-; -----
-#hello_world = (i, j) -> (i, j) size (10, 20, 30) ; expected-error {{more range sizes than range expressions}}
+// -----
+#hello_world = (i, j) -> (i, j) size (10, 20, 30) // expected-error {{more range sizes than range expressions}}
 
-; TODO(bondhugula): Add more tests; coverage of error messages emitted not complete
+// TODO(bondhugula): Add more tests; coverage of error messages emitted not complete
 
-; -----
+// -----
 #ABC = (i,j) -> (i+j)
-#ABC = (i,j) -> (i+j)  ; expected-error {{redefinition of affine map id 'ABC'}}
+#ABC = (i,j) -> (i+j)  // expected-error {{redefinition of affine map id 'ABC'}}
diff --git a/test/IR/parser-affine-map.mlir b/test/IR/parser-affine-map.mlir
index f999afe..a0b550f 100644
--- a/test/IR/parser-affine-map.mlir
+++ b/test/IR/parser-affine-map.mlir
@@ -1,121 +1,121 @@
-; RUN: %S/../../mlir-opt %s -o - | FileCheck %s
+// RUN: %S/../../mlir-opt %s -o - | FileCheck %s
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> (d0, d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) -> (d0, d1)
 #hello_world0 = (i, j) -> (i, j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (d0, d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (d0, d1)
 #hello_world1 = (i, j) [s0] -> (i, j)
 
-; CHECK: #{{[0-9]+}} = () -> (0)
+// CHECK: #{{[0-9]+}} = () -> (0)
 #hello_world2 = () -> (0)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> ((d0 + 1), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) -> ((d0 + 1), d1)
 #hello_world3 = (i, j) -> (i+1, j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((d0 + s0), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((d0 + s0), d1)
 #hello_world4 = (i, j) [s0] -> (i + s0, j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> ((d0 + 1), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) -> ((d0 + 1), d1)
 #hello_world5 = (i, j) -> (1+i, j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((d0 + s0), (d1 + 5))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((d0 + s0), (d1 + 5))
 #hello_world6 = (i, j) [s0] -> (i + s0, j + 5)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (((d0 + d1) + s0), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (((d0 + d1) + s0), d1)
 #hello_world7 = (i, j) [s0] -> (i + j + s0, j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((((d0 + 5) + d1) + s0), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((((d0 + 5) + d1) + s0), d1)
 #hello_world8 = (i, j) [s0] -> (5 + i + j + s0, j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (((d0 + d1) + 5), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (((d0 + d1) + 5), d1)
 #hello_world9 = (i, j) [s0] -> ((i + j) + 5, j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((d0 + (d1 + 5)), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((d0 + (d1 + 5)), d1)
 #hello_world10 = (i, j) [s0] -> (i + (j + 5), j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((d0 * 2), (d1 * 3))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((d0 * 2), (d1 * 3))
 #hello_world11 = (i, j) [s0] -> (2*i, 3*j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (((d0 + 12) + ((d1 + (s0 * 3)) * 5)), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (((d0 + 12) + ((d1 + (s0 * 3)) * 5)), d1)
 #hello_world12 = (i, j) [s0] -> (i + 2*6 + 5*(j+s0*3), j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (((d0 * 5) + d1), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (((d0 * 5) + d1), d1)
 #hello_world13 = (i, j) [s0] -> (5*i + j, j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((d0 + d1), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((d0 + d1), d1)
 #hello_world14 = (i, j) [s0] -> ((i + j), (j))
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (((d0 + d1) + 5), (d1 + 3))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (((d0 + d1) + 5), (d1 + 3))
 #hello_world15 = (i, j) [s0] -> ((i + j)+5, (j)+3)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (d0, 0)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (d0, 0)
 #hello_world16 = (i, j) [s1] -> (i, 0)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (d0, (d1 * s0))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (d0, (d1 * s0))
 #hello_world17 = (i, j) [s0] -> (i, s0*j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> (d0, ((d0 * 3) + d1))
+// CHECK: #{{[0-9]+}} = (d0, d1) -> (d0, ((d0 * 3) + d1))
 #hello_world19 = (i, j) -> (i, 3*i + j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> (d0, (d0 + (d1 * 3)))
+// CHECK: #{{[0-9]+}} = (d0, d1) -> (d0, (d0 + (d1 * 3)))
 #hello_world20 = (i, j)  -> (i, i + 3*j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (d0, (((d0 * ((s0 * s0) * 9)) + 2) + 1))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> (d0, (((d0 * ((s0 * s0) * 9)) + 2) + 1))
 #hello_world18 = (i, j) [N] -> (i, 2 + N*N*9*i + 1)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> (1, ((d0 + (d1 * 3)) + 5))
+// CHECK: #{{[0-9]+}} = (d0, d1) -> (1, ((d0 + (d1 * 3)) + 5))
 #hello_world21 = (i, j)  -> (1, i + 3*j + 5)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((s0 * 5), ((d0 + (d1 * 3)) + (d0 * 5)))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0] -> ((s0 * 5), ((d0 + (d1 * 3)) + (d0 * 5)))
 #hello_world22 = (i, j) [s0] -> (5*s0, i + 3*j + 5*i)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> ((d0 * (s0 * s1)), d1)
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> ((d0 * (s0 * s1)), d1)
 #hello_world23 = (i, j) [s0, s1] -> (i*(s0*s1), j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, (d1 mod 5))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, (d1 mod 5))
 #hello_world24 = (i, j) [s0, s1] -> (i, j mod 5)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, (d1 floordiv 5))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, (d1 floordiv 5))
 #hello_world25 = (i, j) [s0, s1] -> (i, j floordiv 5)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, (d1 ceildiv 5))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, (d1 ceildiv 5))
 #hello_world26 = (i, j) [s0, s1] -> (i, j ceildiv 5)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, ((d0 - d1) - 5))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, ((d0 - d1) - 5))
 #hello_world29 = (i, j) [s0, s1] -> (i, i - j - 5)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, ((d0 - (d1 * s1)) + 2))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, ((d0 - (d1 * s1)) + 2))
 #hello_world30 = (i, j) [M, N] -> (i, i - N*j + 2)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> ((d0 * -5), (d1 * -3), -2, ((d0 + d1) * -1), (s0 * -1))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> ((d0 * -5), (d1 * -3), -2, ((d0 + d1) * -1), (s0 * -1))
 #hello_world32 = (i, j) [s0, s1] -> (-5*i, -3*j, -2, -1*(i+j), -1*s0)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> (-4, (d0 * -1))
+// CHECK: #{{[0-9]+}} = (d0, d1) -> (-4, (d0 * -1))
 #hello_world33 = (i, j) -> (-2+-5-(-3), -1*i)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, (d1 floordiv s0), (d1 mod s0))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, (d1 floordiv s0), (d1 mod s0))
 #hello_world34 = (i, j) [s0, s1] -> (i, j floordiv s0, j mod s0)
 
-; CHECK: #{{[0-9]+}} = (d0, d1, d2) [s0, s1, s2] -> (((((d0 * s1) * s2) + (d1 * s1)) + d2))
+// CHECK: #{{[0-9]+}} = (d0, d1, d2) [s0, s1, s2] -> (((((d0 * s1) * s2) + (d1 * s1)) + d2))
 #hello_world35 = (i, j, k) [s0, s1, s2] -> (i*s1*s2 + j*s1 + k)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> (8, 4, 1, 3, 2, 4)
+// CHECK: #{{[0-9]+}} = (d0, d1) -> (8, 4, 1, 3, 2, 4)
 #hello_world36 = (i, j) -> (5+3, 2*2, 8-7, 100 floordiv 32, 5 mod 3, 10 ceildiv 3)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> (4, 11, 512, 15)
+// CHECK: #{{[0-9]+}} = (d0, d1) -> (4, 11, 512, 15)
 #hello_world37 = (i, j) -> (5 mod 3 + 2, 5*3 - 4, 128 * (500 ceildiv 128), 40 floordiv 7 * 3)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> (((d0 * 2) + 1), (d1 + 2))
+// CHECK: #{{[0-9]+}} = (d0, d1) -> (((d0 * 2) + 1), (d1 + 2))
 #hello_world38 = (i, j) -> (1 + i*2, 2 + j)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> ((d0 * s0), (d0 + s0), (d0 + 2), (d1 * 2), (s1 * 2), (s0 + 2))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> ((d0 * s0), (d0 + s0), (d0 + 2), (d1 * 2), (s1 * 2), (s0 + 2))
 #hello_world39 = (i, j) [M, N] -> (i*M, M + i, 2+i, j*2, N*2, 2 + M)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) -> (d0, d1) size (10, 20)
+// CHECK: #{{[0-9]+}} = (d0, d1) -> (d0, d1) size (10, 20)
 #hello_world40 = (i, j) -> (i, j) size (10, 20)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, d1) size (s0, (s1 + 10))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, d1) size (s0, (s1 + 10))
 #hello_world41 = (i, j) [N, M] -> (i, j) size (N, M+10)
 
-; CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, d1) size (128, (((s0 * 2) + 5) + s1))
+// CHECK: #{{[0-9]+}} = (d0, d1) [s0, s1] -> (d0, d1) size (128, (((s0 * 2) + 5) + s1))
 #hello_world42 = (i, j) [N, M] -> (i, j) size (64 + 64, 5 + 2*N + M)
diff --git a/test/IR/parser-errors.mlir b/test/IR/parser-errors.mlir
index ff3906a..27a53bd 100644
--- a/test/IR/parser-errors.mlir
+++ b/test/IR/parser-errors.mlir
@@ -1,107 +1,107 @@
-; TODO(andydavis) Resolve relative path issue w.r.t invoking mlir-opt in RUN
-; statements (perhaps through using lit config substitutions).
-;
-; RUN: %S/../../mlir-opt %s -o - -check-parser-errors
+// TODO(andydavis) Resolve relative path issue w.r.t invoking mlir-opt in RUN
+// statements (perhaps through using lit config substitutions).
+//
+// RUN: %S/../../mlir-opt %s -o - -check-parser-errors
 
-; Check different error cases.
-; -----
+// Check different error cases.
+// -----
 
-extfunc @illegaltype(i) ; expected-error {{expected type}}
+extfunc @illegaltype(i) // expected-error {{expected type}}
 
-; -----
+// -----
 
-extfunc @nestedtensor(tensor<tensor<i8>>) -> () ; expected-error {{expected type}}
+extfunc @nestedtensor(tensor<tensor<i8>>) -> () // expected-error {{expected type}}
 
-; -----
+// -----
 
 cfgfunc @foo()
-cfgfunc @bar() ; expected-error {{expected '{' in CFG function}}
+cfgfunc @bar() // expected-error {{expected '{' in CFG function}}
 
-; -----
+// -----
 
-extfunc missingsigil() -> (i1, affineint, f32) ; expected-error {{expected a function identifier like}}
+extfunc missingsigil() -> (i1, affineint, f32) // expected-error {{expected a function identifier like}}
 
 
-; -----
+// -----
 
 cfgfunc @bad_branch() {
 bb42:
-  br missing  ; expected-error {{reference to an undefined basic block 'missing'}}
+  br missing  // expected-error {{reference to an undefined basic block 'missing'}}
 }
 
-; -----
+// -----
 
 cfgfunc @block_redef() {
 bb42:
   return
-bb42:        ; expected-error {{redefinition of block 'bb42'}}
+bb42:        // expected-error {{redefinition of block 'bb42'}}
   return
 }
 
-; -----
+// -----
 
 cfgfunc @no_terminator() {
 bb40:
   return
 bb41:
-bb42:        ; expected-error {{expected operation name}}
+bb42:        // expected-error {{expected operation name}}
   return
 }
 
-; -----
+// -----
 
 mlfunc @foo()
-mlfunc @bar() ; expected-error {{expected '{' in ML function}}
+mlfunc @bar() // expected-error {{expected '{' in ML function}}
 
-; -----
+// -----
 
 mlfunc @no_return() {
-}        ; expected-error {{ML function must end with return statement}}
+}        // expected-error {{ML function must end with return statement}}
 
-; -----
+// -----
 
-"       ; expected-error {{expected}}
+"       // expected-error {{expected}}
 "
 
-; -----
+// -----
 
-"       ; expected-error {{expected}}
+"       // expected-error {{expected}}
 
-; -----
+// -----
 
 cfgfunc @no_terminator() {
 bb40:
   "foo"()
-  ""()   ; expected-error {{empty operation name is invalid}}
+  ""()   // expected-error {{empty operation name is invalid}}
   return
 }
 
-; -----
+// -----
 
-extfunc @illegaltype(i0) ; expected-error {{invalid integer width}}
+extfunc @illegaltype(i0) // expected-error {{invalid integer width}}
 
-; -----
+// -----
 
 mlfunc @incomplete_for() {
   for
-}        ; expected-error {{expected '{' before statement list}}
+}        // expected-error {{expected '{' before statement list}}
 
-; -----
+// -----
 
 mlfunc @non_statement() {
-  asd   ; expected-error {{expected statement}}
+  asd   // expected-error {{expected statement}}
 }
 
-; -----
+// -----
 
 cfgfunc @malformed_dim() {
 bb42:
-  "dim"(){index: "xyz"}  ; expected-error {{'dim' op requires an integer attribute named 'index'}}
+  "dim"(){index: "xyz"}  // expected-error {{'dim' op requires an integer attribute named 'index'}}
   return
 }
 
-; -----
+// -----
 
-#map = (d0) -> (%  ; expected-error {{invalid SSA name}}
+#map = (d0) -> (%  // expected-error {{invalid SSA name}}
 
-; -----
+// -----
diff --git a/test/IR/parser.mlir b/test/IR/parser.mlir
index 71d4b56..4ba9aa4 100644
--- a/test/IR/parser.mlir
+++ b/test/IR/parser.mlir
@@ -1,107 +1,107 @@
-; TODO(andydavis) Resolve relative path issue w.r.t invoking mlir-opt in RUN
-; statements (perhaps through using lit config substitutions).
-;
-; RUN: %S/../../mlir-opt %s -o - | FileCheck %s
+// TODO(andydavis) Resolve relative path issue w.r.t invoking mlir-opt in RUN
+// statements (perhaps through using lit config substitutions).
+//
+// RUN: %S/../../mlir-opt %s -o - | FileCheck %s
 
 
-; CHECK: extfunc @foo(i32, i64) -> f32
+// CHECK: extfunc @foo(i32, i64) -> f32
 extfunc @foo(i32, i64) -> f32
 
-; CHECK: extfunc @bar()
+// CHECK: extfunc @bar()
 extfunc @bar() -> ()
 
-; CHECK: extfunc @baz() -> (i1, affineint, f32)
+// CHECK: extfunc @baz() -> (i1, affineint, f32)
 extfunc @baz() -> (i1, affineint, f32)
 
-; CHECK: extfunc @missingReturn()
+// CHECK: extfunc @missingReturn()
 extfunc @missingReturn()
 
-; CHECK: extfunc @int_types(i1, i2, i4, i7, i87) -> (i1, affineint, i19)
+// CHECK: extfunc @int_types(i1, i2, i4, i7, i87) -> (i1, affineint, i19)
 extfunc @int_types(i1, i2, i4, i7, i87) -> (i1, affineint, i19)
 
 
-; CHECK: extfunc @vectors(vector<1xf32>, vector<2x4xf32>)
+// CHECK: extfunc @vectors(vector<1xf32>, vector<2x4xf32>)
 extfunc @vectors(vector<1 x f32>, vector<2x4xf32>)
 
-; CHECK: extfunc @tensors(tensor<??f32>, tensor<??vector<2x4xf32>>, tensor<1x?x4x?x?xaffineint>, tensor<i8>)
+// CHECK: extfunc @tensors(tensor<??f32>, tensor<??vector<2x4xf32>>, tensor<1x?x4x?x?xaffineint>, tensor<i8>)
 extfunc @tensors(tensor<?? f32>, tensor<?? vector<2x4xf32>>,
                  tensor<1x?x4x?x?xaffineint>, tensor<i8>)
 
-; CHECK: extfunc @memrefs(i1, i1)
+// CHECK: extfunc @memrefs(i1, i1)
 extfunc @memrefs(memref<1x?x4x?x?xaffineint>, memref<i8>)
 
-; CHECK: extfunc @functions((i1, i1) -> (), () -> ())
+// CHECK: extfunc @functions((i1, i1) -> (), () -> ())
 extfunc @functions((memref<1x?x4x?x?xaffineint>, memref<i8>) -> (), ()->())
 
 
-; CHECK-LABEL: cfgfunc @simpleCFG(i32, f32) {
+// CHECK-LABEL: cfgfunc @simpleCFG(i32, f32) {
 cfgfunc @simpleCFG(i32, f32) {
-bb42(%0: i32, %f: f32):     ; CHECK: bb0:
-  %1 = "foo"(%0)            ; CHECK: "foo"()
-  "bar"(%1, %f)             ; CHECK: "bar"()
-  return                    ; CHECK: return
-}                           ; CHECK: }
+bb42(%0: i32, %f: f32):     // CHECK: bb0:
+  %1 = "foo"(%0)            // CHECK: "foo"()
+  "bar"(%1, %f)             // CHECK: "bar"()
+  return                    // CHECK: return
+}                           // CHECK: }
 
-; CHECK-LABEL: cfgfunc @multiblock() -> i32 {
+// CHECK-LABEL: cfgfunc @multiblock() -> i32 {
 cfgfunc @multiblock() -> i32 {
-bb0:         ; CHECK: bb0:
-  return     ; CHECK:   return
-bb1:         ; CHECK: bb1:
-  br bb4     ; CHECK:   br bb3
-bb2:         ; CHECK: bb2:
-  br bb2     ; CHECK:   br bb2
-bb4:         ; CHECK: bb3:
-  return     ; CHECK:   return
-}            ; CHECK: }
+bb0:         // CHECK: bb0:
+  return     // CHECK:   return
+bb1:         // CHECK: bb1:
+  br bb4     // CHECK:   br bb3
+bb2:         // CHECK: bb2:
+  br bb2     // CHECK:   br bb2
+bb4:         // CHECK: bb3:
+  return     // CHECK:   return
+}            // CHECK: }
 
-; CHECK-LABEL: mlfunc @simpleMLF() {
+// CHECK-LABEL: mlfunc @simpleMLF() {
 mlfunc @simpleMLF() {
-  return     ; CHECK:  return
-}            ; CHECK: }
+  return     // CHECK:  return
+}            // CHECK: }
 
-; CHECK-LABEL: mlfunc @loops() {
+// CHECK-LABEL: mlfunc @loops() {
 mlfunc @loops() {
-  for {      ; CHECK:   for {
-    for {    ; CHECK:     for {
-    }        ; CHECK:     }
-  }          ; CHECK:   }
-  return     ; CHECK:   return
-}            ; CHECK: }
+  for {      // CHECK:   for {
+    for {    // CHECK:     for {
+    }        // CHECK:     }
+  }          // CHECK:   }
+  return     // CHECK:   return
+}            // CHECK: }
 
-; CHECK-LABEL: mlfunc @ifstmt() {
+// CHECK-LABEL: mlfunc @ifstmt() {
 mlfunc @ifstmt() {
-  for {             ; CHECK   for {
-    if () {         ; CHECK     if () {
-    } else if () {  ; CHECK     } else if () {
-    } else {        ; CHECK     } else {
-    }               ; CHECK     }
-  }                 ; CHECK   }
-  return            ; CHECK   return
-}                   ; CHECK }
+  for {             // CHECK   for {
+    if () {         // CHECK     if () {
+    } else if () {  // CHECK     } else if () {
+    } else {        // CHECK     } else {
+    }               // CHECK     }
+  }                 // CHECK   }
+  return            // CHECK   return
+}                   // CHECK }
 
-; CHECK-LABEL: cfgfunc @attributes() {
+// CHECK-LABEL: cfgfunc @attributes() {
 cfgfunc @attributes() {
-bb42:       ; CHECK: bb0:
+bb42:       // CHECK: bb0:
 
-  ; CHECK: "foo"()
+  // CHECK: "foo"()
   "foo"(){}
 
-  ; CHECK: "foo"(){a: 1, b: -423, c: [true, false]}
+  // CHECK: "foo"(){a: 1, b: -423, c: [true, false]}
   "foo"(){a: 1, b: -423, c: [true, false] }
 
-  ; CHECK: "foo"(){cfgfunc: [], i123: 7, if: "foo"}
+  // CHECK: "foo"(){cfgfunc: [], i123: 7, if: "foo"}
   "foo"(){if: "foo", cfgfunc: [], i123: 7}
 
   return
 }
 
-; CHECK-LABEL: cfgfunc @standard_instrs() {
+// CHECK-LABEL: cfgfunc @standard_instrs() {
 cfgfunc @standard_instrs() {
-bb42:       ; CHECK: bb0:
-  ; CHECK: dim xxx, 2 : sometype
+bb42:       // CHECK: bb0:
+  // CHECK: dim xxx, 2 : sometype
   %a = "dim"(%42){index: 2}
 
-  ; CHECK: addf xx, yy : sometype
+  // CHECK: addf xx, yy : sometype
   "addf"()
   return
 }