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tcg/i386: Use MOVDQA for TCG_TYPE_V128 load/store

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 <= 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 <richard.henderson@linaro.org>
tags/v4.1.0-rc0
Richard Henderson 3 months ago
parent
commit
11e2bfef79
1 changed files with 22 additions and 2 deletions
  1. 22
    2
      tcg/i386/tcg-target.inc.c

+ 22
- 2
tcg/i386/tcg-target.inc.c View File

@@ -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 >= 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 >= 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 >= 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 >= 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 >= 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 >= 16);
tcg_out_vex_modrm_offset(s, OPC_MOVDQU_WxVx | P_VEXL,
arg, 0, arg1, arg2);

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