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	Commit message (Collapse)	Author	Age	Files	Lines
*	MIPS: lib: Provide MIPS64r6 __multi3() for GCC < 7	Paul Burton	2018-08-21	1	-3/+3
\| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \| \|	Some versions of GCC suboptimally generate calls to the __multi3() intrinsic for MIPS64r6 builds, resulting in link failures due to the missing function: LD vmlinux.o MODPOST vmlinux.o kernel/bpf/verifier.o: In function `kmalloc_array': include/linux/slab.h:631: undefined reference to `__multi3' fs/select.o: In function `kmalloc_array': include/linux/slab.h:631: undefined reference to `__multi3' ... We already have a workaround for this in which we provide the instrinsic, but we do so selectively for GCC 7 only. Unfortunately the issue occurs with older GCC versions too - it has been observed with both GCC 5.4.0 & GCC 6.4.0. MIPSr6 support was introduced in GCC 5, so all major GCC versions prior to GCC 8 are affected and we extend our workaround accordingly to all MIPS64r6 builds using GCC versions older than GCC 8. Signed-off-by: Paul Burton <paul.burton@mips.com> Reported-by: Vladimir Kondratiev <vladimir.kondratiev@intel.com> Fixes: ebabcf17bcd7 ("MIPS: Implement __multi3 for GCC7 MIPS64r6 builds") Patchwork: https://patchwork.linux-mips.org/patch/20297/ Cc: James Hogan <jhogan@kernel.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org # 4.15+
*	MIPS: Implement __multi3 for GCC7 MIPS64r6 builds	James Hogan	2018-01-11	1	-0/+54
	GCC7 is a bit too eager to generate suboptimal __multi3 calls (128bit multiply with 128bit result) for MIPS64r6 builds, even in code which doesn't explicitly use 128bit types, such as the following: unsigned long func(unsigned long a, unsigned long b) { return a > (~0UL) / b; } Which GCC rearanges to: return (unsigned __int128)a * (unsigned __int128)b > 0xffffffffffffffff; Therefore implement __multi3, but only for MIPS64r6 with GCC7 as under normal circumstances we wouldn't expect any calls to __multi3 to be generated from kernel code. Reported-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Signed-off-by: James Hogan <jhogan@kernel.org> Tested-by: Waldemar Brodkorb <wbx@openadk.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Maciej W. Rozycki <macro@mips.com> Cc: Matthew Fortune <matthew.fortune@mips.com> Cc: Florian Fainelli <florian@openwrt.org> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/17890/