X87: [turbofan] Fix invalid comparison operator narrowing.

  port a7581443 (r38231)

  original commit message:
  When we narrow a signed32 comparison to uint8 or uint16 representation,
  we also need to change the condition to unsigned comparisons otherwise
  the comparison will be done on int16/int8 which interprets the narrowed
  bits wrong.

BUG=

Review-Url: https://codereview.chromium.org/2206913002
Cr-Commit-Position: refs/heads/master@{#38274}

src/compiler/x87/instruction-selector-x87.cc

@@ -1211,10 +1211,7 @@ void VisitCompare(InstructionSelector* selector, InstructionCode opcode,
 // Tries to match the size of the given opcode to that of the operands, if
 // possible.
 InstructionCode TryNarrowOpcodeSize(InstructionCode opcode, Node* left,
-                                    Node* right) {
-  if (opcode != kX87Cmp && opcode != kX87Test) {
-    return opcode;
-  }
+                                    Node* right, FlagsContinuation* cont) {
   // Currently, if one of the two operands is not a Load, we don't know what its
   // machine representation is, so we bail out.
   // TODO(epertoso): we can probably get some size information out of immediates
@@ -1224,19 +1221,39 @@ InstructionCode TryNarrowOpcodeSize(InstructionCode opcode, Node* left,
   }
   // If the load representations don't match, both operands will be
   // zero/sign-extended to 32bit.
-  LoadRepresentation left_representation = LoadRepresentationOf(left->op());
-  if (left_representation != LoadRepresentationOf(right->op())) {
-    return opcode;
-  }
-  switch (left_representation.representation()) {
-    case MachineRepresentation::kBit:
-    case MachineRepresentation::kWord8:
-      return opcode == kX87Cmp ? kX87Cmp8 : kX87Test8;
-    case MachineRepresentation::kWord16:
-      return opcode == kX87Cmp ? kX87Cmp16 : kX87Test16;
-    default:
-      return opcode;
+  MachineType left_type = LoadRepresentationOf(left->op());
+  MachineType right_type = LoadRepresentationOf(right->op());
+  if (left_type == right_type) {
+    switch (left_type.representation()) {
+      case MachineRepresentation::kBit:
+      case MachineRepresentation::kWord8: {
+        if (opcode == kX87Test) return kX87Test8;
+        if (opcode == kX87Cmp) {
+          if (left_type.semantic() == MachineSemantic::kUint32) {
+            cont->OverwriteUnsignedIfSigned();
+          } else {
+            CHECK_EQ(MachineSemantic::kInt32, left_type.semantic());
+          }
+          return kX87Cmp8;
+        }
+        break;
+      }
+      case MachineRepresentation::kWord16:
+        if (opcode == kX87Test) return kX87Test16;
+        if (opcode == kX87Cmp) {
+          if (left_type.semantic() == MachineSemantic::kUint32) {
+            cont->OverwriteUnsignedIfSigned();
+          } else {
+            CHECK_EQ(MachineSemantic::kInt32, left_type.semantic());
+          }
+          return kX87Cmp16;
+        }
+        break;
+      default:
+        break;
+    }
   }
+  return opcode;
 }
 
 // Shared routine for multiple float32 compare operations (inputs commuted).
@@ -1287,7 +1304,8 @@ void VisitWordCompare(InstructionSelector* selector, Node* node,
   Node* left = node->InputAt(0);
   Node* right = node->InputAt(1);
 
-  InstructionCode narrowed_opcode = TryNarrowOpcodeSize(opcode, left, right);
+  InstructionCode narrowed_opcode =
+      TryNarrowOpcodeSize(opcode, left, right, cont);
 
   int effect_level = selector->GetEffectLevel(node);
   if (cont->IsBranch()) {