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tcg/arm: Support unaligned access for softmmu 

From armv6, the architecture supports unaligned accesses.
All we need to do is perform the correct alignment check
in tcg_out_tlb_read.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2021-08-07 18:19:14 -10:00
parent 367d43d85b
commit 8821ec2323
1 changed files with 21 additions and 20 deletions
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41
tcg/arm/tcg-target.c.inc
View File

@ -1396,16 +1396,9 @@ static TCGReg tcg_out_tlb_read(TCGContext *s, TCGReg addrlo, TCGReg addrhi,
int cmp_off = (is_load ? offsetof(CPUTLBEntry, addr_read)
: offsetof(CPUTLBEntry, addr_write));
int fast_off = TLB_MASK_TABLE_OFS(mem_index);
unsigned s_bits = opc & MO_SIZE;
unsigned a_bits = get_alignment_bits(opc);
/*
* We don't support inline unaligned acceses, but we can easily
* support overalignment checks.
*/
if (a_bits < s_bits) {
a_bits = s_bits;
}
unsigned s_mask = (1 << (opc & MO_SIZE)) - 1;
unsigned a_mask = (1 << get_alignment_bits(opc)) - 1;
TCGReg t_addr;
/* Load env_tlb(env)->f[mmu_idx].{mask,table} into {r0,r1}. */
tcg_out_ldrd_8(s, COND_AL, TCG_REG_R0, TCG_AREG0, fast_off);
@ -1440,27 +1433,35 @@ static TCGReg tcg_out_tlb_read(TCGContext *s, TCGReg addrlo, TCGReg addrhi,
/*
* Check alignment, check comparators.
* Do this in no more than 3 insns. Use MOVW for v7, if possible,
* Do this in 2-4 insns. Use MOVW for v7, if possible,
* to reduce the number of sequential conditional instructions.
* Almost all guests have at least 4k pages, which means that we need
* to clear at least 9 bits even for an 8-byte memory, which means it
* isn't worth checking for an immediate operand for BIC.
*
* For unaligned accesses, test the page of the last unit of alignment.
* This leaves the least significant alignment bits unchanged, and of
* course must be zero.
*/
t_addr = addrlo;
if (a_mask < s_mask) {
t_addr = TCG_REG_R0;
tcg_out_dat_imm(s, COND_AL, ARITH_ADD, t_addr,
addrlo, s_mask - a_mask);
}
if (use_armv7_instructions && TARGET_PAGE_BITS <= 16) {
tcg_target_ulong mask = ~(TARGET_PAGE_MASK | ((1 << a_bits) - 1));
tcg_out_movi32(s, COND_AL, TCG_REG_TMP, mask);
tcg_out_movi32(s, COND_AL, TCG_REG_TMP, ~(TARGET_PAGE_MASK | a_mask));
tcg_out_dat_reg(s, COND_AL, ARITH_BIC, TCG_REG_TMP,
addrlo, TCG_REG_TMP, 0);
t_addr, TCG_REG_TMP, 0);
tcg_out_dat_reg(s, COND_AL, ARITH_CMP, 0, TCG_REG_R2, TCG_REG_TMP, 0);
} else {
if (a_bits) {
tcg_out_dat_imm(s, COND_AL, ARITH_TST, 0, addrlo,
(1 << a_bits) - 1);
if (a_mask) {
tcg_debug_assert(a_mask <= 0xff);
tcg_out_dat_imm(s, COND_AL, ARITH_TST, 0, addrlo, a_mask);
}
tcg_out_dat_reg(s, COND_AL, ARITH_MOV, TCG_REG_TMP, 0, addrlo,
tcg_out_dat_reg(s, COND_AL, ARITH_MOV, TCG_REG_TMP, 0, t_addr,
SHIFT_IMM_LSR(TARGET_PAGE_BITS));
tcg_out_dat_reg(s, (a_bits ? COND_EQ : COND_AL), ARITH_CMP,
tcg_out_dat_reg(s, (a_mask ? COND_EQ : COND_AL), ARITH_CMP,
0, TCG_REG_R2, TCG_REG_TMP,
SHIFT_IMM_LSL(TARGET_PAGE_BITS));
}