Make it possible to skip several passes

Author: vouillon

src/tools/optimization-options.h

@@ -293,7 +293,7 @@ struct OptimizationOptions : public ToolOptions {
            "-sp",
            "Skip a pass (do not run it)",
            OptimizationOptionsCategory,
-           Options::Arguments::One,
+           Options::Arguments::N,
            [this](Options*, const std::string& pass) {
              passOptions.passesToSkip.insert(pass);
            });

test/lit/passes/O1_skip_passes.wast

@@ -0,0 +1,71 @@
+;; RUN: foreach %s %t wasm-opt -O2 --skip-pass=coalesce-locals --skip-pass=simplify-locals--skip-pass=simplify-locals-nostructure -S -o - 2>&1 | filecheck %s
+
+;; Check that we can skip several passes. Note that no local.tee is introduced.
+
+;; There should also be no warning in the output.
+;; CHECK-NOT: warning:
+
+(module
+ ;; CHECK:      (type $0 (func (param i32 i32)))
+
+ ;; CHECK:      (type $1 (func (param i32)))
+
+ ;; CHECK:      (import "a" "b" (func $log (param i32 i32)))
+ (import "a" "b" (func $log (param i32 i32)))
+
+ (func $foo (export "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 $foo))
+
+;; CHECK:      (func $foo (param $p i32)
+;; CHECK-NEXT:  (local $x i32)
+;; CHECK-NEXT:  (local $y i32)
+;; CHECK-NEXT:  (local.set $x
+;; CHECK-NEXT:   (i32.add
+;; CHECK-NEXT:    (local.get $p)
+;; CHECK-NEXT:    (i32.const 1)
+;; CHECK-NEXT:   )
+;; CHECK-NEXT:  )
+;; CHECK-NEXT:  (call $log
+;; CHECK-NEXT:   (local.get $x)
+;; CHECK-NEXT:   (local.get $x)
+;; CHECK-NEXT:  )
+;; CHECK-NEXT:  (local.set $y
+;; CHECK-NEXT:   (i32.add
+;; CHECK-NEXT:    (local.get $p)
+;; CHECK-NEXT:    (i32.const 1)
+;; CHECK-NEXT:   )
+;; CHECK-NEXT:  )
+;; CHECK-NEXT:  (call $log
+;; CHECK-NEXT:   (local.get $y)
+;; CHECK-NEXT:   (local.get $y)
+;; CHECK-NEXT:  )
+;; CHECK-NEXT: )