[PATCH, GCC/ARM, 1/10] Fix -mcmse check in libgcc

[Mihail Ionescu <mihail dot ionescu at foss dot arm dot com>]

[PATCH, GCC/ARM, 1/10] Fix -mcmse check in libgcc

Hi,

=== Context ===

This patch is part of a patch series to add support for Armv8.1-M
Mainline Security Extensions architecture. Its purpose is to fix the
check to determine whether -mcmse is supported by the host compiler.

=== Patch description ===

Code to detect whether cmse.c can be buit with -mcmse checks the output
of host GCC when invoked with -mcmse. However, an error from the
compiler does not prevent some minimal output so this always holds true.

This does not affect currently supported architectures since the test is
guarded by __ARM_FEATURE_CMSE which is only defined for Armv8-M Baseline
and Mainline and these two architectures accept -mcmse.

However, in the intermediate patches adding support for Armv8.1-M
Mainline, support for Security Extensions is disabled until fully
implemented. This leads to libgcc/config/arm/cmse.c being built with
-mcmse due to the broken test which fails in the intermediate commits.

This patch instead change the test to look at the return value of the
host gcc when invoked with -mcmse.


ChangeLog entry is as follows:

*** libgcc/ChangeLog ***

2019-10-23  Mihail-Calin Ionescu  <mihail.ionescu@arm.com>
2019-10-23  Thomas Preud'homme  <thomas.preudhomme@arm.com>

	* config/arm/t-arm: Check return value of gcc rather than lack of
	output.

Testing: Bootstrapped and tested on arm-none-eabi.
Without this patch, GCC stops building after the second patch
of this series.

Is this ok for trunk?

Best regards,

Mihail


###############     Attachment also inlined for ease of reply    ###############


diff --git a/libgcc/config/arm/t-arm b/libgcc/config/arm/t-arm
index 274bf2a8ef33c5e8a8ee2b246aba92d30297abe1..f2b927f3686a8c0a8e37abfe2d7768f2050d4fb3 100644
--- a/libgcc/config/arm/t-arm
+++ b/libgcc/config/arm/t-arm
@@ -3,7 +3,7 @@ LIB1ASMFUNCS = _thumb1_case_sqi _thumb1_case_uqi _thumb1_case_shi \
 	_thumb1_case_uhi _thumb1_case_si _speculation_barrier
 
 HAVE_CMSE:=$(findstring __ARM_FEATURE_CMSE,$(shell $(gcc_compile_bare) -dM -E - </dev/null))
-ifneq ($(shell $(gcc_compile_bare) -E -mcmse - </dev/null 2>/dev/null),)
+ifeq ($(shell $(gcc_compile_bare) -E -mcmse - </dev/null >/dev/null 2>/dev/null; echo $?),0)
 CMSE_OPTS:=-mcmse
 endif

Attachment: diff00.patch
Description: Text document