[cleanup] Drop Runtime_IsValidSmi

It only had one callsite, and that callsite was useless:
%IsValidSmi(two_31) has never returned {true} on any
configuration we have ever shipped.

Bug: v8:10933
Change-Id: I09cdfd7bbd7960d1ec460ad4bd9f0d21e47f7393
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2434746
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70285}

src/runtime/runtime-numbers.cc

@@ -13,15 +13,6 @@
 namespace v8 {
 namespace internal {
 
-RUNTIME_FUNCTION(Runtime_IsValidSmi) {
-  SealHandleScope shs(isolate);
-  DCHECK_EQ(1, args.length());
-
-  CONVERT_NUMBER_CHECKED(int32_t, number, Int32, args[0]);
-  return isolate->heap()->ToBoolean(Smi::IsValid(number));
-}
-
-
 RUNTIME_FUNCTION(Runtime_StringToNumber) {
   HandleScope handle_scope(isolate);
   DCHECK_EQ(1, args.length());

src/runtime/runtime.h

@@ -276,7 +276,6 @@ namespace internal {
   F(GetHoleNaNLower, 0, 1)               \
   F(GetHoleNaNUpper, 0, 1)               \
   I(IsSmi, 1, 1)                         \
-  F(IsValidSmi, 1, 1)                    \
   F(MaxSmi, 0, 1)                        \
   F(NumberToStringSlow, 1, 1)            \
   F(StringParseFloat, 1, 1)              \

test/mjsunit/smi-mul-const.js

@@ -73,16 +73,14 @@ assertUnoptimized(mul_by_2);
 
 // Deopt on overflow.
 
-// 2^30 is a smi boundary on arm and ia32.
+// -2^30 is in Smi range on most configurations, +2^30 is not.
 var two_30 = 1 << 30;
-// 2^31 is a smi boundary on arm64 and x64.
-var two_31 = 2 * two_30;
+assertEquals(two_30, mul_by_neg_1(-two_30));
 
-// TODO(rmcilroy): replace after r16361 with:  if (%IsValidSmi(two_31)) {
-if (true) {
-  assertEquals(two_31, mul_by_neg_1(-two_31));
-  assertUnoptimized(mul_by_neg_1);
-} else {
-  assertEquals(two_30, mul_by_neg_1(-two_30));
-  assertUnoptimized(mul_by_neg_1);
-}
+// For good measure, check that overflowing int32 range (or Smi range
+// without pointer compression) works too.
+var two_31 = two_30 * 2;
+assertEquals(two_31, mul_by_neg_1(-two_31));
+
+// One of the two situations deoptimized the code.
+assertUnoptimized(mul_by_neg_1);

test/mjsunit/smi-mul.js

@@ -53,17 +53,14 @@ mul2(-1, 2);
 mul2(-1, 2);
 %OptimizeFunctionOnNextCall(mul2);
 
-// 2^30 is a smi boundary on arm and ia32.
+// -2^30 is in Smi range on most configurations, +2^30 is not.
 var two_30 = 1 << 30;
-// 2^31 is a smi boundary on x64.
-var two_31 = 2 * two_30;
+assertEquals(two_30, mul2(-two_30, -1));
 
-if (%IsValidSmi(two_31)) {
-  // Deopt on two_31 on x64.
-  assertEquals(two_31, mul2(-two_31, -1));
-  assertUnoptimized(mul2);
-} else {
-  // Deopt on two_30 on ia32.
-  assertEquals(two_30, mul2(-two_30, -1));
-  assertUnoptimized(mul2);
-}
+// For good measure, check that overflowing int32 range (or Smi range
+// without pointer compression) works too.
+var two_31 = two_30 * 2;
+assertEquals(two_31, mul2(-two_31, -1));
+
+// One of the two situations deoptimized the code.
+assertUnoptimized(mul2);