[Coverage] Test lowering of ill-formed SIL profiling intrinsics

This adds a test case to exercise a path in IRGen which discards
ill-formed profiling intrinsics.

rdar://40133800 & r://39146527

Author: vedantk

test/Profiler/instrprof_symtab_valid.sil

@@ -0,0 +1,30 @@
+// RUN: %target-swift-frontend -assume-parsing-unqualified-ownership-sil %s -profile-generate -profile-coverage-mapping -emit-ir -o - -module-name=irgen | %FileCheck %s
+
+// CHECK-NOT: @__llvm_coverage_mapping
+
+sil_stage canonical
+
+import Builtin
+import Swift
+import SwiftShims
+
+// main
+sil @main : $@convention(c) (Int32, UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>) -> Int32 {
+bb0(%0 : $Int32, %1 : $UnsafeMutablePointer<Optional<UnsafeMutablePointer<Int8>>>):
+  %2 = string_literal utf8 "<stdin>:__tlcd_line:1:1" // user: %6
+  %3 = integer_literal $Builtin.Int64, 0          // user: %6
+  %4 = integer_literal $Builtin.Int32, 2          // user: %6
+  %5 = integer_literal $Builtin.Int32, 0          // user: %6
+
+  // Pass an invalid SIL value to the int_instrprof_increment intrinsic
+  // to force IRGen to drop it.
+  %6 = builtin "int_instrprof_increment"(%3 : $Builtin.Int64, %3 : $Builtin.Int64, %4 : $Builtin.Int32, %5 : $Builtin.Int32) : $()
+
+  return %0 : $Int32                             // id: %33
+} // end sil function 'main'
+
+sil_coverage_map "<stdin>" "__tlcd_line:1:1" "<stdin>:__tlcd_line:1:1" 0 {	// __tlcd_line:1:1
+  1:19 -> 1:20 : 1
+  1:23 -> 1:24 : (0 - 1)
+  1:1 -> 1:24 : 0
+}