[stubs] Add SmiMax and refactor SmiMin to use Select

SmiMax will be used in a follow-up commit.

BUG=

Review-Url: https://codereview.chromium.org/2372543002
Cr-Commit-Position: refs/heads/master@{#39783}

src/code-stub-assembler.cc

@@ -349,19 +349,12 @@ Node* CodeStubAssembler::SmiLessThanOrEqual(Node* a, Node* b) {
   return IntPtrLessThanOrEqual(a, b);
 }
 
+Node* CodeStubAssembler::SmiMax(Node* a, Node* b) {
+  return Select(SmiLessThan(a, b), b, a);
+}
+
 Node* CodeStubAssembler::SmiMin(Node* a, Node* b) {
-  // TODO(bmeurer): Consider using Select once available.
-  Variable min(this, MachineRepresentation::kTagged);
-  Label if_a(this), if_b(this), join(this);
-  BranchIfSmiLessThan(a, b, &if_a, &if_b);
-  Bind(&if_a);
-  min.Bind(a);
-  Goto(&join);
-  Bind(&if_b);
-  min.Bind(b);
-  Goto(&join);
-  Bind(&join);
-  return min.value();
+  return Select(SmiLessThan(a, b), a, b);
 }
 
 Node* CodeStubAssembler::SmiMod(Node* a, Node* b) {

src/code-stub-assembler.h

@@ -120,6 +120,7 @@ class CodeStubAssembler : public compiler::CodeAssembler {
   compiler::Node* SmiAboveOrEqual(compiler::Node* a, compiler::Node* b);
   compiler::Node* SmiLessThan(compiler::Node* a, compiler::Node* b);
   compiler::Node* SmiLessThanOrEqual(compiler::Node* a, compiler::Node* b);
+  compiler::Node* SmiMax(compiler::Node* a, compiler::Node* b);
   compiler::Node* SmiMin(compiler::Node* a, compiler::Node* b);
   // Computes a % b for Smi inputs a and b; result is not necessarily a Smi.
   compiler::Node* SmiMod(compiler::Node* a, compiler::Node* b);