PPC/s390: [wasm-simd] Implement rounding average for ia32

Port cb4ff11d

R=zhin@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: I830f055201e8fe873b3e7721d4c117715f620f14
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1991321Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#65637}

src/compiler/backend/ppc/instruction-selector-ppc.cc

@@ -2193,6 +2193,14 @@ void InstructionSelector::VisitI16x8GtU(Node* node) { UNIMPLEMENTED(); }
 
 void InstructionSelector::VisitI16x8GeU(Node* node) { UNIMPLEMENTED(); }
 
+void InstructionSelector::VisitI16x8RoundingAverageU(Node* node) {
+  UNIMPLEMENTED();
+}
+
+void InstructionSelector::VisitI8x16RoundingAverageU(Node* node) {
+  UNIMPLEMENTED();
+}
+
 void InstructionSelector::VisitI8x16Neg(Node* node) { UNIMPLEMENTED(); }
 
 void InstructionSelector::VisitI8x16Splat(Node* node) { UNIMPLEMENTED(); }

src/compiler/backend/s390/instruction-selector-s390.cc

@@ -2655,6 +2655,14 @@ void InstructionSelector::VisitI16x8GtU(Node* node) { UNIMPLEMENTED(); }
 
 void InstructionSelector::VisitI16x8GeU(Node* node) { UNIMPLEMENTED(); }
 
+void InstructionSelector::VisitI16x8RoundingAverageU(Node* node) {
+  UNIMPLEMENTED();
+}
+
+void InstructionSelector::VisitI8x16RoundingAverageU(Node* node) {
+  UNIMPLEMENTED();
+}
+
 void InstructionSelector::VisitI8x16Neg(Node* node) { UNIMPLEMENTED(); }
 
 void InstructionSelector::VisitI8x16AddSaturateS(Node* node) {