ARM64: Reland faster immediate check

src/arm64/macro-assembler-arm64.cc

Index: src/arm64/macro-assembler-arm64.cc
diff --git a/src/arm64/macro-assembler-arm64.cc b/src/arm64/macro-assembler-arm64.cc
index eb8f0d282ef43f5056d80a367ed53cc01d99bc97..8c3587d3d7fb088d42c815d7b9a60981ca7f9ac3 100644
--- a/src/arm64/macro-assembler-arm64.cc
+++ b/src/arm64/macro-assembler-arm64.cc
@@ -64,17 +64,23 @@ void MacroAssembler::LogicalMacro(const Register& rd,
   } else if (operand.IsImmediate()) {
     int64_t immediate = operand.ImmediateValue();
     unsigned reg_size = rd.SizeInBits();
-    ASSERT(rd.Is64Bits() || is_uint32(immediate));
 
     // If the operation is NOT, invert the operation and immediate.
     if ((op & NOT) == NOT) {
       op = static_cast<LogicalOp>(op & ~NOT);
       immediate = ~immediate;
-      if (rd.Is32Bits()) {
-        immediate &= kWRegMask;
-      }
     }
 
+    // Ignore the top 32 bits of an immediate if we're moving to a W register.
+    if (rd.Is32Bits()) {
+      // Check that the top 32 bits are consistent.
+      ASSERT(((immediate >> kWRegSizeInBits) == 0) ||
+             ((immediate >> kWRegSizeInBits) == -1));
+      immediate &= kWRegMask;
+    }
+
+    ASSERT(rd.Is64Bits() || is_uint32(immediate));
+
     // Special cases for all set or all clear immediates.
     if (immediate == 0) {
       switch (op) {