https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83653
Bug ID: 83653
Summary: GCC fails to remove a can't-happen call on ia64
Product: gcc
Version: 6.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: matthew at wil dot cx
Target Milestone: ---
Created attachment 43009
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43009&action=edit
Gzipped preprocessed source
This is an excerpt from the Linux kernel, with some patches that I'm preparing
to go in. The 0day build-bot reports a problem with an undefined
__bad_increment_for_ia64_fetch_and_add.
I can reproduce the problem by taking the attached preprocessed source and
compiling it with gcc -O2 -o shmem.o -c shmem.i and then running nm shmem.o
|grep __bad
Manually inlining page_ref_sub() in the included test-case makes the problem go
away, as does simply deleting the call to page_ref_sub() (at line 50756).
Command line: gcc -Wp,-MD,mm/.shmem.o.d -nostdinc -isystem
/usr/lib/gcc/ia64-linux-gnu/4.6/include -I./arch/ia64/include
-I./arch/ia64/include/generated -I./include -I./arch/ia64/include/uapi
-I./arch/ia64/include/generated/uapi -I./include/uapi
-I./include/generated/uapi -include ./include/linux/kconfig.h -D__KERNEL__
-DHAVE_WORKING_TEXT_ALIGN -DHAVE_MODEL_SMALL_ATTRIBUTE
-DHAVE_SERIALIZE_DIRECTIVE -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs
-fno-strict-aliasing -fno-common -fshort-wchar
-Werror-implicit-function-declaration -Wno-format-security -std=gnu89
-Wno-unused-but-set-variable -fno-PIE -pipe -ffixed-r13
-mfixed-range=f12-f15,f32-f127 -falign-functions=32 -frename-registers
-fno-optimize-sibling-calls -fno-delete-null-pointer-checks -O2
-DCC_HAVE_ASM_GOTO -Wframe-larger-than=2048 -fno-stack-protector
-fomit-frame-pointer -fno-var-tracking-assignments -g
-Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow
-fno-stack-check -fconserve-stack -Werror=implicit-int
-Werror=strict-prototypes -Werror=date-time -Werror=incompatible-pointer-types
-Werror=designated-init -mconstant-gp -DKBUILD_BASENAME='"shmem"'
-DKBUILD_MODNAME='"shmem"' -c -o mm/.tmp_shmem.o mm/shmem.c
