rust: compile libcore with no_fp_fmt_parse

This option removes floating point formatting/parsing support in
`libcore`, thus allows us to remove the intrinsics stubs in
`compiler_builtins.rs` and saves some space.

   text	   data	    bss	    dec	filename
6282838	2277360	 296600	8856798	w/o `no_fp_fmt_parse`
6235608	2250128	 296600	8782336	w/  `no_fp_fmt_parse`

Signed-off-by: Gary Guo <[email protected]>

Author: nbdd0121

rust/Makefile

@@ -326,6 +326,7 @@ $(objtree)/rust/kernel.o: $(srctree)/rust/kernel/lib.rs $(objtree)/rust/alloc.o
 # Targets that need to expand twice
 .SECONDEXPANSION:
 $(objtree)/rust/core.o: private skip_clippy = 1
+$(objtree)/rust/core.o: private rustc_target_flags = --cfg no_fp_fmt_parse
 $(objtree)/rust/core.o: $$(RUST_LIB_SRC)/core/src/lib.rs FORCE
 	$(call if_changed_dep,rustc_library)
 

rust/compiler_builtins.rs

@@ -36,84 +36,6 @@ macro_rules! define_panicking_intrinsics(
     }
 );
 
-define_panicking_intrinsics!("`f32` should not be used", {
-    __addsf3,
-    __addsf3vfp,
-    __aeabi_fcmpeq,
-    __aeabi_ul2f,
-    __divsf3,
-    __divsf3vfp,
-    __eqsf2,
-    __eqsf2vfp,
-    __fixsfdi,
-    __fixsfsi,
-    __fixsfti,
-    __fixunssfdi,
-    __fixunssfsi,
-    __fixunssfti,
-    __floatdisf,
-    __floatsisf,
-    __floattisf,
-    __floatundisf,
-    __floatunsisf,
-    __floatuntisf,
-    __gesf2,
-    __gesf2vfp,
-    __gtsf2,
-    __gtsf2vfp,
-    __lesf2,
-    __lesf2vfp,
-    __ltsf2,
-    __ltsf2vfp,
-    __mulsf3,
-    __mulsf3vfp,
-    __nesf2,
-    __nesf2vfp,
-    __powisf2,
-    __subsf3,
-    __subsf3vfp,
-    __unordsf2,
-});
-
-define_panicking_intrinsics!("`f64` should not be used", {
-    __adddf3,
-    __adddf3vfp,
-    __aeabi_dcmpeq,
-    __aeabi_ul2d,
-    __divdf3,
-    __divdf3vfp,
-    __eqdf2,
-    __eqdf2vfp,
-    __fixdfdi,
-    __fixdfsi,
-    __fixdfti,
-    __fixunsdfdi,
-    __fixunsdfsi,
-    __fixunsdfti,
-    __floatdidf,
-    __floatsidf,
-    __floattidf,
-    __floatundidf,
-    __floatunsidf,
-    __floatuntidf,
-    __gedf2,
-    __gedf2vfp,
-    __gtdf2,
-    __gtdf2vfp,
-    __ledf2,
-    __ledf2vfp,
-    __ltdf2,
-    __ltdf2vfp,
-    __muldf3,
-    __muldf3vfp,
-    __nedf2,
-    __nedf2vfp,
-    __powidf2,
-    __subdf3,
-    __subdf3vfp,
-    __unorddf2,
-});
-
 define_panicking_intrinsics!("`i128` should not be used", {
     __ashrti3,
     __muloti4,