Warning improvements (#2438)

If wasm-opt is run with no passes, warn, as we've gotten reports that people
assume a tool called "wasm-opt" should optimize automatically (but we follow
llvm's opt convention of not doing so).

Add a --quiet (-q) flag that suppresses this minor warning, and the other minor
warning where there is no output file.

1 files changed, 8 insertions, 2 deletions

diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index 33e9a0396..b2d1f2c14 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -318,7 +318,11 @@ int main(int argc, const char* argv[]) {
     curr = &other;
   }
 
-  if (options.runningPasses()) {
+  if (!options.runningPasses()) {
+    if (!options.quiet) {
+      std::cerr << "warning: no passes specified, not doing any work\n";
+    }
+  } else {
     if (options.debug) {
       std::cerr << "running passes...\n";
     }
@@ -363,7 +367,9 @@ int main(int argc, const char* argv[]) {
   }
 
   if (options.extra.count("output") == 0) {
-    std::cerr << "no output file specified, not emitting output\n";
+    if (!options.quiet) {
+      std::cerr << "warning: no output file specified, not emitting output\n";
+    }
     return 0;
   }