gcc 5.4.0-6ubuntu1~16.04.4 internal compiler error: in simplify_binary_operation_1, at simplify-rtx.c:3619

[Colin Ian King]

When building stress-ng (from git://kernel.ubuntu.com/cking/stress-ng) the PPA builder for Xenial with gcc 5.4.0-6ubuntu1~16.04.4 on ppc64el breaks with an internal compiler error when building vector math code with __int128_t types.

cc -g -O3 -fstack-protector-strong -Wformat -Werror=format-security -Wall -Wextra -DVERSION="0.07.25" -O2 -std=gnu99 -DHAVE_APPARMOR -DHAVE_LIB_BSD -DHAVE_LIB_Z -DHAVE_LIB_CRYPT -DHAVE_LIB_RT -DHAVE_LIB_PTHREAD -DHAVE_LIB_SCTP -DHAVE_LIB_AIO -DHAVE_KEYUTILS_H -DHAVE_XATTR_H -DHAVE_SECCOMP_H -DHAVE_SYS_CAP_H -DHAVE_FLOAT_DECIMAL -DHAVE_VECMATH -DHAVE_ATOMIC -DHAVE_ASM_NOP -fno-builtin -c -o stress-vecmath.o stress-vecmath.c
stress-vecmath.c: In function ‘stress_vecmath’:
stress-vecmath.c:181:1: internal compiler error: in simplify_binary_operation_1, at simplify-rtx.c:3619
 }
 ^

The source code that trips this issue: http://kernel.ubuntu.com/git/cking/stress-ng.git/tree/stress-vecmath.c

This builds OK on Yakkety upwards.

Attached is the full build log from the PPA.

[Anton Blanchard (anton-samba)]

Reduced test case:

typedef __uint128_t vint128_t __attribute__((vector_size(16)));
vint128_t z;
int x, y;

void fn2(void);

void fn1(void)
{
        vint128_t c;
        y = 1000;
        for (; y; y--) {
                c = c ^ x;
                z -= c;
                z ^= x;
                c = c ^ x;
        }

        fn2();
}

[Anton Blanchard (anton-samba)]

Build with gcc -g -O2

[Matthias Klose (doko)]

work around is to build with -O1