ir/bits.h cleanups after #2879 (#3156)

Improve some comments, and remove fast paths that are just optimizations for compile time (code clarity matters more here).
WebAssembly · Sep 22, 2020 · 0f9339d · 0f9339d
1 parent b410773
commit 0f9339d
Showing 1 changed file with 11 additions and 19 deletions.
diff --git a/src/ir/bits.h b/src/ir/bits.h
@@ -176,7 +176,7 @@ Index getMaxBits(Expression* curr,
       case RemSInt32: {
         if (auto* c = binary->right->dynCast<Const>()) {
           auto maxBitsLeft = getMaxBits(binary->left, localInfoProvider);
-          // if maxBitsLeft is negative
+          // if left may be negative, the result may be negative
           if (maxBitsLeft == 32) {
             return 32;
           }
@@ -199,12 +199,8 @@ Index getMaxBits(Expression* curr,
       }
       case OrInt32:
       case XorInt32: {
-        auto maxBits = getMaxBits(binary->right, localInfoProvider);
-        // if maxBits is negative
-        if (maxBits == 32) {
-          return 32;
-        }
-        return std::max(getMaxBits(binary->left, localInfoProvider), maxBits);
+        return std::max(getMaxBits(binary->left, localInfoProvider),
+                        getMaxBits(binary->right, localInfoProvider));
       }
       case ShlInt32: {
         if (auto* shifts = binary->right->dynCast<Const>()) {
@@ -227,7 +223,7 @@ Index getMaxBits(Expression* curr,
       case ShrSInt32: {
         if (auto* shift = binary->right->dynCast<Const>()) {
           auto maxBits = getMaxBits(binary->left, localInfoProvider);
-          // if maxBits is negative
+          // if left may be negative, the result may be negative
           if (maxBits == 32) {
             return 32;
           }
@@ -255,7 +251,7 @@ Index getMaxBits(Expression* curr,
       case DivSInt64: {
         if (auto* c = binary->right->dynCast<Const>()) {
           int32_t maxBitsLeft = getMaxBits(binary->left, localInfoProvider);
-          // if maxBitsLeft or right const value is negative
+          // if left or right const value is negative
           if (maxBitsLeft == 64 || c->value.geti64() < 0) {
             return 64;
           }
@@ -275,7 +271,7 @@ Index getMaxBits(Expression* curr,
       case RemSInt64: {
         if (auto* c = binary->right->dynCast<Const>()) {
           auto maxBitsLeft = getMaxBits(binary->left, localInfoProvider);
-          // if maxBitsLeft is negative
+          // if left may be negative, the result may be negative
           if (maxBitsLeft == 64) {
             return 64;
           }
@@ -293,17 +289,13 @@ Index getMaxBits(Expression* curr,
         return 64;
       }
       case AndInt64: {
-        auto maxBits = getMaxBits(binary->right, localInfoProvider);
-        return std::min(getMaxBits(binary->left, localInfoProvider), maxBits);
+        return std::min(getMaxBits(binary->left, localInfoProvider),
+                        getMaxBits(binary->right, localInfoProvider));
       }
       case OrInt64:
       case XorInt64: {
-        auto maxBits = getMaxBits(binary->right, localInfoProvider);
-        // if maxBits is negative
-        if (maxBits == 64) {
-          return 64;
-        }
-        return std::max(getMaxBits(binary->left, localInfoProvider), maxBits);
+        return std::max(getMaxBits(binary->left, localInfoProvider),
+                        getMaxBits(binary->right, localInfoProvider));
       }
       case ShlInt64: {
         if (auto* shifts = binary->right->dynCast<Const>()) {
@@ -326,7 +318,7 @@ Index getMaxBits(Expression* curr,
       case ShrSInt64: {
         if (auto* shift = binary->right->dynCast<Const>()) {
           auto maxBits = getMaxBits(binary->left, localInfoProvider);
-          // if maxBits is negative
+          // if left may be negative, the result may be negative
           if (maxBits == 64) {
             return 64;
           }