[Liftoff] Implement float promotion and demotion

Add support for f32.demote/f64 and f64.promote/f32.
Both are straight forward to implement on ia32 and x64.

R=titzer@chromium.org

Bug: v8:6600
Change-Id: I75213ddf5f422d0aa1d5d9a3bbc90ac32f6950f5
Reviewed-on: https://chromium-review.googlesource.com/955849
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51872}

src/wasm/baseline/ia32/liftoff-assembler-ia32.h

@@ -707,12 +707,18 @@ bool LiftoffAssembler::emit_type_conversion(WasmOpcode opcode,
       Cvtui2ss(dst.fp(), src.gp(), scratch);
       return true;
     }
+    case kExprF32ConvertF64:
+      cvtsd2ss(dst.fp(), src.fp());
+      return true;
     case kExprF64SConvertI32:
       Cvtsi2sd(dst.fp(), src.gp());
       return true;
     case kExprF64UConvertI32:
       LoadUint32(dst.fp(), src.gp());
       return true;
+    case kExprF64ConvertF32:
+      cvtss2sd(dst.fp(), src.fp());
+      return true;
     default:
       return false;
   }

src/wasm/baseline/liftoff-compiler.cc

@@ -638,12 +638,14 @@ class LiftoffCompiler {
                              &ExternalReference::wasm_int64_to_float32)
         CASE_TYPE_CONVERSION(F32UConvertI64, F32, I64,
                              &ExternalReference::wasm_uint64_to_float32)
+        CASE_TYPE_CONVERSION(F32ConvertF64, F32, F64, nullptr)
         CASE_TYPE_CONVERSION(F64SConvertI32, F64, I32, nullptr)
         CASE_TYPE_CONVERSION(F64UConvertI32, F64, I32, nullptr)
         CASE_TYPE_CONVERSION(F64SConvertI64, F64, I64,
                              &ExternalReference::wasm_int64_to_float64)
         CASE_TYPE_CONVERSION(F64UConvertI64, F64, I64,
                              &ExternalReference::wasm_uint64_to_float64)
+        CASE_TYPE_CONVERSION(F64ConvertF32, F64, F32, nullptr)
       default:
         return unsupported(decoder, WasmOpcodes::OpcodeName(opcode));
     }

src/wasm/baseline/x64/liftoff-assembler-x64.h

@@ -658,6 +658,9 @@ bool LiftoffAssembler::emit_type_conversion(WasmOpcode opcode,
     case kExprF32UConvertI64:
       Cvtqui2ss(dst.fp(), src.gp(), kScratchRegister);
       return true;
+    case kExprF32ConvertF64:
+      Cvtsd2ss(dst.fp(), src.fp());
+      return true;
     case kExprF64SConvertI32:
       Cvtlsi2sd(dst.fp(), src.gp());
       return true;
@@ -671,6 +674,9 @@ bool LiftoffAssembler::emit_type_conversion(WasmOpcode opcode,
     case kExprF64UConvertI64:
       Cvtqui2sd(dst.fp(), src.gp(), kScratchRegister);
       return true;
+    case kExprF64ConvertF32:
+      Cvtss2sd(dst.fp(), src.fp());
+      return true;
     default:
       UNREACHABLE();
   }