PPC/s390: [wasm-simd] Implement floating-point roundings

Port 068cf20e

Original Commit Message:

    Implement f32x4 and f64x2 nearest, trunc, ceil, and floor.

    These instructions were accepted into the proposal [0], this change
    removes all the ifdefs and todo guarding the prototypes, and moves these
    instructions out of the post-mvp flag.

    [0] https://github.com/WebAssembly/simd/pull/232

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

Change-Id: I02086255f635f1d47586fc74dd754426f6beccb0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2411675Reviewed-by: Milad Farazmand <mfarazma@redhat.com>
Reviewed-by: Junliang Yan <junyan@redhat.com>
Commit-Queue: Milad Farazmand <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/master@{#69925}

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

@@ -2411,6 +2411,22 @@ void InstructionSelector::VisitI16x8BitMask(Node* node) { UNIMPLEMENTED(); }
 
 void InstructionSelector::VisitI32x4BitMask(Node* node) { UNIMPLEMENTED(); }
 
+void InstructionSelector::VisitF64x2Ceil(Node* node) { UNIMPLEMENTED(); }
+
+void InstructionSelector::VisitF64x2Floor(Node* node) { UNIMPLEMENTED(); }
+
+void InstructionSelector::VisitF64x2Trunc(Node* node) { UNIMPLEMENTED(); }
+
+void InstructionSelector::VisitF64x2NearestInt(Node* node) { UNIMPLEMENTED(); }
+
+void InstructionSelector::VisitF32x4Ceil(Node* node) { UNIMPLEMENTED(); }
+
+void InstructionSelector::VisitF32x4Floor(Node* node) { UNIMPLEMENTED(); }
+
+void InstructionSelector::VisitF32x4Trunc(Node* node) { UNIMPLEMENTED(); }
+
+void InstructionSelector::VisitF32x4NearestInt(Node* node) { UNIMPLEMENTED(); }
+
 void InstructionSelector::EmitPrepareResults(
     ZoneVector<PushParameter>* results, const CallDescriptor* call_descriptor,
     Node* node) {