Inlining: Always inline single-use functions

src/pass.h

@@ -69,9 +69,10 @@ struct InliningOptions {
   // More generally, with 2 items we may have a local.get, but no way to
   // require it to be saved instead of directly consumed.
   Index alwaysInlineMaxSize = 2;
-  // Function size which we inline when there is only one caller.
-  // FIXME: this should logically be higher than flexibleInlineMaxSize.
-  Index oneCallerInlineMaxSize = 15;
+  // Function size which we inline when there is only one caller. By default we
+  // inline all such functions (as after inlining we can remove the original
+  // function).
+  Index oneCallerInlineMaxSize = -1;
   // Function size above which we never inline, ignoring the various flexible
   // factors (like whether we are optimizing for size or speed) that could
   // influence us.

src/tools/optimization-options.h

@@ -155,13 +155,12 @@ struct OptimizationOptions : public ToolOptions {
       .add("--one-caller-inline-max-function-size",
            "-ocimfs",
            "Max size of functions that are inlined when there is only one "
-           "caller (default " +
-             std::to_string(InliningOptions().oneCallerInlineMaxSize) +
-             "). Reason this is not unbounded is that some "
-             "implementations may have a hard time optimizing really large "
-             "functions",
+           "caller (default -1, which means all such functions are inlined)",
            Options::Arguments::One,
            [this](Options* o, const std::string& argument) {
+             static_assert(InliningOptions().oneCallerInlineMaxSize ==
+                             Index(-1),
+                           "the help text here is written to assume -1");
              passOptions.inlining.oneCallerInlineMaxSize =
                static_cast<Index>(atoi(argument.c_str()));
            })

test/binaryen.js/inlining-options.js.txt

@@ -1,4 +1,4 @@
 // alwaysInlineMaxSize=2
 // flexibleInlineMaxSize=20
-// oneCallerInlineMaxSize=15
+// oneCallerInlineMaxSize=-1
 // allowInliningFunctionsWithLoops=false