8316893: Compile without -fno-delete-null-pointer-checks

Reviewed-by: kbarrett, erikj

make/autoconf/flags-cflags.m4

@@ -799,15 +799,6 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_CPU_DEP],
     $1_TOOLCHAIN_CFLAGS="${$1_GCC6_CFLAGS}"
 
     $1_WARNING_CFLAGS_JVM="-Wno-format-zero-length -Wtype-limits -Wuninitialized"
-  elif test "x$TOOLCHAIN_TYPE" = xclang; then
-    NO_DELETE_NULL_POINTER_CHECKS_CFLAG="-fno-delete-null-pointer-checks"
-    FLAGS_COMPILER_CHECK_ARGUMENTS(ARGUMENT: [$NO_DELETE_NULL_POINTER_CHECKS_CFLAG],
-        PREFIX: $3,
-        IF_FALSE: [
-            NO_DELETE_NULL_POINTER_CHECKS_CFLAG=
-        ]
-    )
-    $1_TOOLCHAIN_CFLAGS="${NO_DELETE_NULL_POINTER_CHECKS_CFLAG}"
   fi
 
   if test "x$TOOLCHAIN_TYPE" = xmicrosoft; then
@@ -929,17 +920,12 @@ AC_DEFUN([FLAGS_SETUP_CFLAGS_CPU_DEP],
 # $2 - Prefix for compiler variables (either BUILD_ or nothing).
 AC_DEFUN([FLAGS_SETUP_GCC6_COMPILER_FLAGS],
 [
-  # These flags are required for GCC 6 builds as undefined behavior in OpenJDK code
-  # runs afoul of the more aggressive versions of these optimizations.
-  # Notably, value range propagation now assumes that the this pointer of C++
-  # member functions is non-null.
-  NO_DELETE_NULL_POINTER_CHECKS_CFLAG="-fno-delete-null-pointer-checks"
-  FLAGS_COMPILER_CHECK_ARGUMENTS(ARGUMENT: [$NO_DELETE_NULL_POINTER_CHECKS_CFLAG],
-      PREFIX: $2, IF_FALSE: [NO_DELETE_NULL_POINTER_CHECKS_CFLAG=""])
+  # This flag is required for GCC 6 builds as undefined behavior in OpenJDK code
+  # runs afoul of the more aggressive versions of this optimization.
   NO_LIFETIME_DSE_CFLAG="-fno-lifetime-dse"
   FLAGS_COMPILER_CHECK_ARGUMENTS(ARGUMENT: [$NO_LIFETIME_DSE_CFLAG],
       PREFIX: $2, IF_FALSE: [NO_LIFETIME_DSE_CFLAG=""])
-  $1_GCC6_CFLAGS="${NO_DELETE_NULL_POINTER_CHECKS_CFLAG} ${NO_LIFETIME_DSE_CFLAG}"
+  $1_GCC6_CFLAGS="${NO_LIFETIME_DSE_CFLAG}"
 ])
 
 AC_DEFUN_ONCE([FLAGS_SETUP_BRANCH_PROTECTION],