[SILGen] Make #file to respect #sourceLocation (swiftlang#5425)

Code

  func foo(f: String = #file) {
    print(f)
  }
  #sourceLocation(file: "virtual.swift", line: 1)
  foo()

should print "virtual.swift"

lib/SILGen/SILGenApply.cpp

@@ -4764,10 +4764,8 @@ RValue SILGenFunction::emitLiteral(LiteralExpr *literal, SGFContext C) {
     switch (magicLiteral->getKind()) {
     case MagicIdentifierLiteralExpr::File: {
       StringRef value = "";
-      if (loc.isValid()) {
-        unsigned bufferID = ctx.SourceMgr.findBufferContainingLoc(loc);
-        value = ctx.SourceMgr.getIdentifierForBuffer(bufferID);
-      }
+      if (loc.isValid())
+        value = ctx.SourceMgr.getBufferIdentifierForLoc(loc);
       builtinLiteralArgs = emitStringLiteral(*this, literal, value, C,
                                              magicLiteral->getStringEncoding());
       builtinInit = magicLiteral->getBuiltinInitializer();

test/SILGen/source_location.swift

@@ -0,0 +1,23 @@
+// RUN: %target-swift-frontend -Xllvm -sil-full-demangle -emit-silgen %s | %FileCheck %s
+
+func printSourceLocation(file: String = #file, line: Int = #line) {}
+
+#sourceLocation(file: "caller.swift", line: 10000)
+_ = printSourceLocation()
+// CHECK: [[PRINT_SOURCE_LOCATION:%.*]] = function_ref @_TF15source_location19printSourceLocationFT4fileSS4lineSi_T_
+// CHECK: [[CALLER_FILE_VAL:%.*]] = string_literal utf16 "caller.swift",
+// CHECK: [[CALLER_FILE:%.*]] = apply {{.*}}([[CALLER_FILE_VAL]],
+// CHECK: [[CALLER_LINE_VAL:%.*]] = integer_literal $Builtin.Int{{[0-9]+}}, 10000,
+// CHECK: [[CALLER_LINE:%.*]] = apply {{.*}}([[CALLER_LINE_VAL]],
+// CHECK: apply [[PRINT_SOURCE_LOCATION]]([[CALLER_FILE]], [[CALLER_LINE]])
+
+#sourceLocation(file: "inplace.swift", line: 20000)
+let FILE = #file, LINE = #line
+// CHECK: [[FILE_ADDR:%.*]] = global_addr @_Tv15source_location4FILESS
+// CHECK: [[INPLACE_FILE_VAL:%.*]] = string_literal utf16 "inplace.swift",
+// CHECK: [[INPLACE_FILE:%.*]] = apply {{.*}}([[INPLACE_FILE_VAL]],
+// CHECK: store [[INPLACE_FILE]] to [[FILE_ADDR]]
+// CHECK: [[LINE_ADDR:%.*]] = global_addr @_Tv15source_location4LINESi
+// CHECK: [[INPLACE_LINE_VAL:%.*]] = integer_literal $Builtin.Int{{[0-9]+}}, 20000,
+// CHECK: [[INPLACE_LINE:%.*]] = apply {{.*}}([[INPLACE_LINE_VAL]],
+// CHECK: store [[INPLACE_LINE]] to [[LINE_ADDR]]