8024050: Incorrect optimization level and comment specified for unsafe.cpp

Summary: Fix comments and optimization level.
Reviewed-by: rdurbin, coleenp, hseigel
Contributed-by: lois.foltan@oracle.com

make/bsd/makefiles/gcc.make

@@ -129,13 +129,17 @@ ifeq ($(USE_CLANG), true)
   
     # We only use precompiled headers for the JVM build
     CFLAGS += $(VM_PCH_FLAG)
-  
-    # There are some files which don't like precompiled headers
-    # The following files are build with 'OPT_CFLAGS/NOOPT' (-O0) in the opt build.
-    # But Clang doesn't support a precompiled header which was compiled with -O3
-    # to be used in a compilation unit which uses '-O0'. We could also prepare an
-    # extra '-O0' PCH file for the opt build and use it here, but it's probably
-    # not worth the effort as long as only two files need this special handling.
+ 
+    # The following files are compiled at various optimization
+    # levels due to optimization issues encountered at the
+    # 'OPT_CFLAGS_DEFAULT' level. The Clang compiler issues a compile
+    # time error if there is an optimization level specification
+    # skew between the PCH file and the C++ file.  Especially if the
+    # PCH file is compiled at a higher optimization level than
+    # the C++ file.  One solution might be to prepare extra optimization
+    # level specific PCH files for the opt build and use them here, but
+    # it's probably not worth the effort as long as only a few files
+    # need this special handling.
     PCH_FLAG/loopTransform.o = $(PCH_FLAG/NO_PCH)
     PCH_FLAG/sharedRuntimeTrig.o = $(PCH_FLAG/NO_PCH)
     PCH_FLAG/sharedRuntimeTrans.o = $(PCH_FLAG/NO_PCH)
@@ -307,7 +311,7 @@ OPT_CFLAGS/NOOPT=-O0
 ifeq ($(USE_CLANG), true)
   ifeq ($(shell expr $(CC_VER_MAJOR) = 4 \& $(CC_VER_MINOR) = 2), 1)
     OPT_CFLAGS/loopTransform.o += $(OPT_CFLAGS/NOOPT)
-    OPT_CFLAGS/unsafe.o += -01
+    OPT_CFLAGS/unsafe.o += -O1
   endif
 else
   # 6835796. Problem in GCC 4.3.0 with mulnode.o optimized compilation.