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X-Received-From: 2607:f8b0:4864:20::442 Subject: [Qemu-devel] [PATCH 16/16] tcg/i386: Use MOVDQA for TCG_TYPE_V128 load/store X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" This instruction raises #GP, aka SIGSEGV, if the effective address is not aligned to 16-bytes. We have assertions in tcg-op-gvec.c that the offset from ENV is aligned, for vector types <=3D V128. But the offset itself does not validate that the final pointer is aligned -- one must also remember to use the QEMU_ALIGNED() attribute on the vector member within ENV. PowerPC Altivec has vector load/store instructions that silently discard the low 4 bits of the address, making alignment mistakes difficult to discover. Aid that by making the most popular host visibly signal the error. Signed-off-by: Richard Henderson --- tcg/i386/tcg-target.inc.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) diff --git a/tcg/i386/tcg-target.inc.c b/tcg/i386/tcg-target.inc.c index 6ec5e60448..c0443da4af 100644 --- a/tcg/i386/tcg-target.inc.c +++ b/tcg/i386/tcg-target.inc.c @@ -1082,14 +1082,24 @@ static void tcg_out_ld(TCGContext *s, TCGType type,= TCGReg ret, } /* FALLTHRU */ case TCG_TYPE_V64: + /* There is no instruction that can validate 8-byte alignment. */ tcg_debug_assert(ret >=3D 16); tcg_out_vex_modrm_offset(s, OPC_MOVQ_VqWq, ret, 0, arg1, arg2); break; case TCG_TYPE_V128: + /* + * The gvec infrastructure is asserts that v128 vector loads + * and stores use a 16-byte aligned offset. Validate that the + * final pointer is aligned by using an insn that will SIGSEGV. + */ tcg_debug_assert(ret >=3D 16); - tcg_out_vex_modrm_offset(s, OPC_MOVDQU_VxWx, ret, 0, arg1, arg2); + tcg_out_vex_modrm_offset(s, OPC_MOVDQA_VxWx, ret, 0, arg1, arg2); break; case TCG_TYPE_V256: + /* + * The gvec infrastructure only requires 16-byte alignment, + * so here we must use an unaligned load. + */ tcg_debug_assert(ret >=3D 16); tcg_out_vex_modrm_offset(s, OPC_MOVDQU_VxWx | P_VEXL, ret, 0, arg1, arg2); @@ -1117,14 +1127,24 @@ static void tcg_out_st(TCGContext *s, TCGType type,= TCGReg arg, } /* FALLTHRU */ case TCG_TYPE_V64: + /* There is no instruction that can validate 8-byte alignment. */ tcg_debug_assert(arg >=3D 16); tcg_out_vex_modrm_offset(s, OPC_MOVQ_WqVq, arg, 0, arg1, arg2); break; case TCG_TYPE_V128: + /* + * The gvec infrastructure is asserts that v128 vector loads + * and stores use a 16-byte aligned offset. Validate that the + * final pointer is aligned by using an insn that will SIGSEGV. + */ tcg_debug_assert(arg >=3D 16); - tcg_out_vex_modrm_offset(s, OPC_MOVDQU_WxVx, arg, 0, arg1, arg2); + tcg_out_vex_modrm_offset(s, OPC_MOVDQA_WxVx, arg, 0, arg1, arg2); break; case TCG_TYPE_V256: + /* + * The gvec infrastructure only requires 16-byte alignment, + * so here we must use an unaligned store. + */ tcg_debug_assert(arg >=3D 16); tcg_out_vex_modrm_offset(s, OPC_MOVDQU_WxVx | P_VEXL, arg, 0, arg1, arg2); --=20 2.17.1