ARM64: Fixes and more support for FRINT<X> instructions.

src/arm64/assembler-arm64.h

Index: src/arm64/assembler-arm64.h
diff --git a/src/arm64/assembler-arm64.h b/src/arm64/assembler-arm64.h
index 50f86cc3e66747a37e1aa9f4972a3b86d10409c2..9e92b6dae1a05f348c6b65810a0d3588f977cad9 100644
--- a/src/arm64/assembler-arm64.h
+++ b/src/arm64/assembler-arm64.h
@@ -1584,6 +1584,9 @@ class Assembler : public AssemblerBase {
   // FP round to integer (nearest with ties to away).
   void frinta(const FPRegister& fd, const FPRegister& fn);
 
+  // FP round to integer (toward minus infinity).
+  void frintm(const FPRegister& fd, const FPRegister& fn);
+
   // FP round to integer (nearest with ties to even).
   void frintn(const FPRegister& fd, const FPRegister& fn);