[llvm-bugs] [Bug 38886] New: ppc64le clang fails with couldn't allocate output register for constraint

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=38886

            Bug ID: 38886
           Summary: ppc64le clang fails with couldn't allocate output
                    register for constraint
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: joel at jms.id.au
                CC: llvm-bugs at lists.llvm.org

Created attachment 20856
  --> https://bugs.llvm.org/attachment.cgi?id=20856&action=edit
preprocesed source for lib/raid6/vpermxor1.c

When building lib/raid6/vpermxor1.c from the Linux kernel:

lib/raid6/vpermxor1.c:64:8: error: couldn't allocate output register for
constraint 'v'
                        asm(VPERMXOR(%0,%1,%2,%3) : "=v"(wq0) : "v"(gf_high),
"v"(gf_low), "v"(wq0));
                            ^


clang-8 -Wp,-MD,lib/raid6/.vpermxor1.o.d  -nostdinc -isystem
/scratch/joel/llvm-build/lib/clang/8.0.0/include -I./arch/powerpc/include
-I./arch/powerpc/include/generated  -I./include -I./arch/powerpc/include/uapi
-I./arch/powerpc/include/generated/uapi -I./include/uapi
-I./include/generated/uapi -include ./include/linux/kconfig.h -include
./include/linux/compiler_types.h -D__KERNEL__ -Iarch/powerpc -DHAVE_AS_ATHIGH=1
-Qunused-arguments -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs
-fno-strict-aliasing -fno-common -fshort-wchar
-Werror-implicit-function-declaration -Wno-format-security -std=gnu89
-no-integrated-as -fno-PIE -mlittle-endian -m64 -msoft-float -pipe
-Iarch/powerpc -mabi=elfv2 -mcmodel=medium -mcpu=power8 -mtune=power9
-mno-altivec -mno-vsx -funit-at-a-time -fno-dwarf2-cfi-asm -Wa,-maltivec
-Wa,-mpower8 -mlittle-endian -fno-delete-null-pointer-checks -O2
-Wframe-larger-than=2048 -fno-stack-protector -Wno-format-invalid-specifier
-Wno-gnu -Wno-address-of-packed-member -Wno-tautological-compare
-mno-global-merge -Wno-unused-const-variable -fomit-frame-pointer
-Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow
-fno-merge-all-constants -fno-stack-check -Werror=implicit-int
-Werror=strict-prototypes -Werror=date-time -Werror=incompatible-pointer-types
-Wno-initializer-overrides -Wno-unused-value -Wno-format -Wno-sign-compare
-Wno-format-zero-length -Wno-uninitialized -maltivec -mabi=altivec  -DMODULE 
-mcmodel=large  -DKBUILD_BASENAME='"vpermxor1"' -DKBUILD_MODNAME='"raid6_pq"'
-c -o vpermxor1.o vpermxor1.i

GCC can build the same code. clang can compile a simple program that uses
vpermxor, so I suspect the issue is related to the other operations in the for
loop.

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