[turbofan] Introduce new operators Float32SubPreserveNan and Float64SubPreserveNan for wasm.

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

Index: src/compiler/mips/instruction-selector-mips.cc
diff --git a/src/compiler/mips/instruction-selector-mips.cc b/src/compiler/mips/instruction-selector-mips.cc
index eaa17af7a07c44f714007609b294671736e309b4..cccb39a7549b81d6b9672704d945ac072d6f562e 100644
--- a/src/compiler/mips/instruction-selector-mips.cc
+++ b/src/compiler/mips/instruction-selector-mips.cc
@@ -754,6 +754,9 @@ void InstructionSelector::VisitFloat32Sub(Node* node) {
   VisitRRR(this, kMipsSubS, node);
 }
 
+void InstructionSelector::VisitFloat32SubPreserveNan(Node* node) {
+  VisitRRR(this, kMipsSubS, node);
+}
 
 void InstructionSelector::VisitFloat64Sub(Node* node) {
   MipsOperandGenerator g(this);
@@ -773,6 +776,9 @@ void InstructionSelector::VisitFloat64Sub(Node* node) {
   VisitRRR(this, kMipsSubD, node);
 }
 
+void InstructionSelector::VisitFloat64SubPreserveNan(Node* node) {
+  VisitRRR(this, kMipsSubD, node);
+}
 
 void InstructionSelector::VisitFloat32Mul(Node* node) {
   VisitRRR(this, kMipsMulS, node);