Add a mechanism to skip a pass by name

src/pass.h

@@ -226,6 +226,8 @@ struct PassOptions {
   // Arbitrary string arguments from the commandline, which we forward to
   // passes.
   std::unordered_map<std::string, std::string> arguments;
+  // Passes to skip and not run.
+  std::unordered_set<std::string> passesToSkip;
 
   // Effect info computed for functions. One pass can generate this and then
   // other passes later can benefit from it. It is up to the sequence of passes
@@ -386,6 +388,9 @@ struct PassRunner {
   // Whether this pass runner has run. A pass runner should only be run once.
   bool ran = false;
 
+  // Passes in |options.passesToSkip| that we have seen and skipped.
+  std::unordered_set<std::string> skippedPasses;
+
   void runPass(Pass* pass);
   void runPassOnFunction(Pass* pass, Function* func);
 

src/passes/pass.cpp

@@ -692,6 +692,9 @@ void PassRunner::run() {
   assert(!ran);
   ran = true;
 
+  // As we run passes, we'll notice which we skip.
+  skippedPasses.clear();
+
   static const int passDebug = getPassDebug();
   // Emit logging information when asked for. At passDebug level 1+ we log
   // the main passes, while in 2 we also log nested ones. Note that for
@@ -812,6 +815,16 @@ void PassRunner::run() {
     }
     flush();
   }
+
+  // All the passes the user requested to skip should have been seen, and
+  // skipped. If not, the user may have had a typo in the name of a pass to
+  // skip, and we will warn.
+  for (auto pass : options.passesToSkip) {
+    if (!skippedPasses.count(pass)) {
+      std::cerr << "warning: --" << pass << " was requested to be skipped, "
+                << "but it was not found in the passes that were run.\n";
+    }
+  }
 }
 
 void PassRunner::runOnFunction(Function* func) {
@@ -930,6 +943,13 @@ struct AfterEffectModuleChecker {
 };
 
 void PassRunner::runPass(Pass* pass) {
+  assert(!pass->isFunctionParallel());
+
+  if (options.passesToSkip.count(pass->name)) {
+    skippedPasses.insert(pass->name);
+    return;
+  }
+
   std::unique_ptr<AfterEffectModuleChecker> checker;
   if (getPassDebug()) {
     checker = std::unique_ptr<AfterEffectModuleChecker>(
@@ -949,6 +969,11 @@ void PassRunner::runPass(Pass* pass) {
 void PassRunner::runPassOnFunction(Pass* pass, Function* func) {
   assert(pass->isFunctionParallel());
 
+  if (options.passesToSkip.count(pass->name)) {
+    skippedPasses.insert(pass->name);
+    return;
+  }
+
   auto passDebug = getPassDebug();
 
   // Add extra validation logic in pass-debug mode 2. The main logic in

src/tools/optimization-options.h

@@ -277,6 +277,14 @@ struct OptimizationOptions : public ToolOptions {
            Options::Arguments::Zero,
            [this](Options*, const std::string&) {
              passOptions.zeroFilledMemory = true;
+           })
+      .add("--skip-pass",
+           "-sp",
+           "Skip a pass (do not run it)",
+           OptimizationOptionsCategory,
+           Options::Arguments::One,
+           [this](Options*, const std::string& pass) {
+             passOptions.passesToSkip.insert(pass);
            });
 
     // add passes in registry

test/lit/help/wasm-opt.test

@@ -567,6 +567,8 @@
 ;; CHECK-NEXT:   --zero-filled-memory,-uim                     Assume that an imported memory
 ;; CHECK-NEXT:                                                 will be zero-initialized
 ;; CHECK-NEXT:
+;; CHECK-NEXT:   --skip-pass,-sp                               Skip a pass (do not run it)
+;; CHECK-NEXT:
 ;; CHECK-NEXT:
 ;; CHECK-NEXT: Tool options:
 ;; CHECK-NEXT: -------------

test/lit/help/wasm2js.test

@@ -526,6 +526,8 @@
 ;; CHECK-NEXT:   --zero-filled-memory,-uim                     Assume that an imported memory
 ;; CHECK-NEXT:                                                 will be zero-initialized
 ;; CHECK-NEXT:
+;; CHECK-NEXT:   --skip-pass,-sp                               Skip a pass (do not run it)
+;; CHECK-NEXT:
 ;; CHECK-NEXT:
 ;; CHECK-NEXT: Tool options:
 ;; CHECK-NEXT: -------------

test/lit/passes/O1_skip.wast

@@ -0,0 +1,70 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+;; NOTE: This test was ported using port_passes_tests_to_lit.py and could be cleaned up.
+
+;; RUN: foreach %s %t wasm-opt -O2 --coalesce-locals --skip-pass=coalesce-locals -S -o - | filecheck %s
+
+;; We should skip coalese-locals even though it is run in -O2 and also we ask to
+;; run it directly: the skip instruction overrides everything else.
+
+(module
+ ;; CHECK:      (type $i32_i32_=>_none (func (param i32 i32)))
+
+ ;; CHECK:      (type $i32_=>_none (func (param i32)))
+
+ ;; CHECK:      (import "a" "b" (func $log (param i32 i32)))
+ (import "a" "b" (func $log (param i32 i32)))
+
+ (func "foo" (param $p i32)
+  ;; The locals $x and $y can be coalesced into a single local, but as we do not
+  ;; run that pass, they will not be. Other minor optimizations will occur here,
+  ;; such as using a tee.
+  (local $x i32)
+  (local $y i32)
+
+  (local.set $x
+   (i32.add
+    (local.get $p)
+    (i32.const 1)
+   )
+  )
+  (call $log
+   (local.get $x)
+   (local.get $x)
+  )
+
+  (local.set $y
+   (i32.add
+    (local.get $p)
+    (i32.const 1)
+   )
+  )
+  (call $log
+   (local.get $y)
+   (local.get $y)
+  )
+ )
+)
+;; CHECK:      (export "foo" (func $0))
+
+;; CHECK:      (func $0 (; has Stack IR ;) (param $p i32)
+;; CHECK-NEXT:  (local $x i32)
+;; CHECK-NEXT:  (local $y i32)
+;; CHECK-NEXT:  (call $log
+;; CHECK-NEXT:   (local.tee $x
+;; CHECK-NEXT:    (i32.add
+;; CHECK-NEXT:     (local.get $p)
+;; CHECK-NEXT:     (i32.const 1)
+;; CHECK-NEXT:    )
+;; CHECK-NEXT:   )
+;; CHECK-NEXT:   (local.get $x)
+;; CHECK-NEXT:  )
+;; CHECK-NEXT:  (call $log
+;; CHECK-NEXT:   (local.tee $y
+;; CHECK-NEXT:    (i32.add
+;; CHECK-NEXT:     (local.get $p)
+;; CHECK-NEXT:     (i32.const 1)
+;; CHECK-NEXT:    )
+;; CHECK-NEXT:   )
+;; CHECK-NEXT:   (local.get $y)
+;; CHECK-NEXT:  )
+;; CHECK-NEXT: )

test/lit/passes/skip-missing.wast

@@ -0,0 +1,8 @@
+;; We should warn on a pass called "waka" not having been run and skipped.
+
+;; RUN: wasm-opt %s -O1 --skip-pass=waka 2>&1 | filecheck %s
+
+;; CHECK: warning: --waka was requested to be skipped, but it was not found in the passes that were run.
+
+(module
+)