[LLVMbugs] [Bug 16915] New: __clear_cache builtin is not disable with -fno-builtins on ARM

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=16915

            Bug ID: 16915
           Summary: __clear_cache builtin is not disable with
                    -fno-builtins on ARM
           Product: compiler-rt
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: compiler-rt
          Assignee: unassignedbugs at nondot.org
          Reporter: s_llvm at nedprod.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

This is a slightly difficult bug to explain without being able to supply
source. Still, I'll try.

I've added a new compiler-rt build target which looks like this:

Configs += full-arm asan-arm
Arch.full-arm := arm
Arch.asan-arm := arm

CFLAGS.full-arm = $(CFLAGS) -target armv7-unknown-nto-qnx8.0.0eabi -fno-builtin
-fno-rtti
CFLAGS.asan-arm := $(CFLAGS) -fPIE -fno-builtin -fno-rtti \
    -target armv7-unknown-nto-qnx8.0.0eabi --sysroot=$(QNX_TARGET) -mllvm
-arm-enable-ehabi

FUNCTIONS.full-arm := $(CommonFunctions) $(ArchFunctions.arm)
FUNCTIONS.asan-arm := $(AsanFunctions) $(InterceptionFunctions) \
                                          $(SanitizerCommonFunctions)

So, in other words, I've created a full support library for ARM, and it gets
compiled with -fno-builtin because I'm compiling hard editions of the builtins.

The problem is that trying to compile __clear_cache from lib/clear_cache.c
still errors because I'm trying to reimplement a builtin. I think this is
because the ARM target isn't correctly disabling __clear_cache when
-fno-builtins is specified, and that would be a bug.

To work around it I simply renamed lib/clear_cache.c to
lib/clear_cache.c.disabled and all now works, albeit minus a __clear_cache
implementation in the libclang_rt-full-arm.a.

Niall

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