Make #file only include the filename

This change may have significant code size benefits.

Author: beccadax

lib/SILGen/SILGenApply.cpp

@@ -5134,7 +5134,9 @@ RValue SILGenFunction::emitLiteral(LiteralExpr *literal, SGFContext C) {
       std::string value;
       if (loc.isValid())
         value = ctx.SourceMgr.getDisplayNameForLoc(loc);
-      builtinLiteralArgs = emitStringLiteral(*this, literal, value, C,
+      builtinLiteralArgs = emitStringLiteral(*this, literal,
+                                             llvm::sys::path::filename(value),
+                                             C,
                                              magicLiteral->getStringEncoding());
       builtinInit = magicLiteral->getBuiltinInitializer();
       init = magicLiteral->getInitializer();

test/PlaygroundTransform/implicit_return_never.swift

@@ -13,7 +13,7 @@
 
 func f() -> Int {
     fatalError()
-// CRASH-CHECK: {{[fF]}}atal error: file {{.*}}/main.swift, line [[@LINE-1]]
+// CRASH-CHECK: {{[fF]}}atal error: file main.swift, line [[@LINE-1]]
 }
 
 f()

test/PlaygroundTransform/placeholder.swift

@@ -15,7 +15,7 @@
 func f(crash crash: Bool) -> Int {
   if crash {
     return <#T#>
-    // CRASH-CHECK: {{[fF]}}atal error: attempt to evaluate editor placeholder: file {{.*}}/main.swift, line [[@LINE-1]]
+    // CRASH-CHECK: {{[fF]}}atal error: attempt to evaluate editor placeholder: file main.swift, line [[@LINE-1]]
   } else {
     return 42
   }