I've found several valid invocations of _mm256_cmp_ps() that will make valgrind crash with a VEX error. It turns out that the compare variant (in third parameter) is poorly supported by VEX. For instance, using '_CMP_NEQ_OS' will cause a crash. As does '__CMP_GE_OQ'. However, using ' _CMP_GT_OQ' is fine. There are many possible values for the compare variant: /* Compare */ #define _CMP_EQ_OQ 0x00 /* Equal (ordered, non-signaling) */ #define _CMP_LT_OS 0x01 /* Less-than (ordered, signaling) */ #define _CMP_LE_OS 0x02 /* Less-than-or-equal (ordered, signaling) */ #define _CMP_UNORD_Q 0x03 /* Unordered (non-signaling) */ #define _CMP_NEQ_UQ 0x04 /* Not-equal (unordered, non-signaling) */ #define _CMP_NLT_US 0x05 /* Not-less-than (unordered, signaling) */ #define _CMP_NLE_US 0x06 /* Not-less-than-or-equal (unordered, signaling) */ #define _CMP_ORD_Q 0x07 /* Ordered (nonsignaling) */ #define _CMP_EQ_UQ 0x08 /* Equal (unordered, non-signaling) */ #define _CMP_NGE_US 0x09 /* Not-greater-than-or-equal (unord, signaling) */ #define _CMP_NGT_US 0x0a /* Not-greater-than (unordered, signaling) */ #define _CMP_FALSE_OQ 0x0b /* False (ordered, non-signaling) */ #define _CMP_NEQ_OQ 0x0c /* Not-equal (ordered, non-signaling) */ #define _CMP_GE_OS 0x0d /* Greater-than-or-equal (ordered, signaling) */ #define _CMP_GT_OS 0x0e /* Greater-than (ordered, signaling) */ #define _CMP_TRUE_UQ 0x0f /* True (unordered, non-signaling) */ #define _CMP_EQ_OS 0x10 /* Equal (ordered, signaling) */ #define _CMP_LT_OQ 0x11 /* Less-than (ordered, non-signaling) */ #define _CMP_LE_OQ 0x12 /* Less-than-or-equal (ordered, non-signaling) */ #define _CMP_UNORD_S 0x13 /* Unordered (signaling) */ #define _CMP_NEQ_US 0x14 /* Not-equal (unordered, signaling) */ #define _CMP_NLT_UQ 0x15 /* Not-less-than (unordered, non-signaling) */ #define _CMP_NLE_UQ 0x16 /* Not-less-than-or-equal (unord, non-signaling) */ #define _CMP_ORD_S 0x17 /* Ordered (signaling) */ #define _CMP_EQ_US 0x18 /* Equal (unordered, signaling) */ #define _CMP_NGE_UQ 0x19 /* Not-greater-than-or-equal (unord, non-sign) */ #define _CMP_NGT_UQ 0x1a /* Not-greater-than (unordered, non-signaling) */ #define _CMP_FALSE_OS 0x1b /* False (ordered, signaling) */ #define _CMP_NEQ_OS 0x1c /* Not-equal (ordered, signaling) */ #define _CMP_GE_OQ 0x1d /* Greater-than-or-equal (ordered, non-signaling) */ #define _CMP_GT_OQ 0x1e /* Greater-than (ordered, non-signaling) */ #define _CMP_TRUE_US 0x1f /* True (unordered, signaling) */ Valgrind VEX only supports some of them. vex amd64->IR: unhandled instruction bytes: 0xC4 0x41 0x7C 0xC2 0xEF 0x1C 0xC4 0x41 vex amd64->IR: REX=0 REX.W=0 REX.R=1 REX.X=0 REX.B=1 vex amd64->IR: VEX=1 VEX.L=1 VEX.nVVVV=0x0 ESC=0F vex amd64->IR: PFX.66=0 PFX.F2=0 PFX.F3=0 ==30317== valgrind: Unrecognised instruction at address 0x42b25b.
Fixed, vex r3170. *** This bug has been marked as a duplicate of bug 342571 ***