From: Aurelien Jarno Date: Tue, 9 Oct 2012 19:53:11 +0000 (+0200) Subject: tcg/arm: fix cross-endian qemu_st16 X-Git-Tag: v1.3.0-rc1~46 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=7aab08aa786e3a8838beac758ee61c5000144937;p=qemu.git tcg/arm: fix cross-endian qemu_st16 The bswap16 TCG opcode assumes that the high bytes of the temp equal to 0 before calling it. The ARM backend implementation takes this assumption to slightly optimize the generated code. The same implementation is called for implementing the cross-endian qemu_st16 opcode, where this assumption is not true anymore. One way to fix that would be to zero the high bytes before calling it. Given the store instruction just ignore them, it is possible to provide a slightly more optimized version. With ARMv6+ the rev16 instruction does the work correctly. For lower ARM versions the patch provides a version which behaves correctly with non-zero high bytes, but fill them with junk. Cc: Andrzej Zaborowski Cc: Peter Maydell Cc: qemu-stable@nongnu.org Reviewed-by: Peter Maydell Signed-off-by: Aurelien Jarno --- diff --git a/tcg/arm/tcg-target.c b/tcg/arm/tcg-target.c index 955010271..47612fe26 100644 --- a/tcg/arm/tcg-target.c +++ b/tcg/arm/tcg-target.c @@ -611,6 +611,22 @@ static inline void tcg_out_bswap16(TCGContext *s, int cond, int rd, int rn) } } +/* swap the two low bytes assuming that the two high input bytes and the + two high output bit can hold any value. */ +static inline void tcg_out_bswap16st(TCGContext *s, int cond, int rd, int rn) +{ + if (use_armv6_instructions) { + /* rev16 */ + tcg_out32(s, 0x06bf0fb0 | (cond << 28) | (rd << 12) | rn); + } else { + tcg_out_dat_reg(s, cond, ARITH_MOV, + TCG_REG_R8, 0, rn, SHIFT_IMM_LSR(8)); + tcg_out_dat_imm(s, cond, ARITH_AND, TCG_REG_R8, TCG_REG_R8, 0xff); + tcg_out_dat_reg(s, cond, ARITH_ORR, + rd, TCG_REG_R8, rn, SHIFT_IMM_LSL(8)); + } +} + static inline void tcg_out_bswap32(TCGContext *s, int cond, int rd, int rn) { if (use_armv6_instructions) { @@ -1367,7 +1383,7 @@ static inline void tcg_out_qemu_st(TCGContext *s, const TCGArg *args, int opc) break; case 1: if (bswap) { - tcg_out_bswap16(s, COND_EQ, TCG_REG_R0, data_reg); + tcg_out_bswap16st(s, COND_EQ, TCG_REG_R0, data_reg); tcg_out_st16_r(s, COND_EQ, TCG_REG_R0, addr_reg, TCG_REG_R1); } else { tcg_out_st16_r(s, COND_EQ, data_reg, addr_reg, TCG_REG_R1); @@ -1453,7 +1469,7 @@ static inline void tcg_out_qemu_st(TCGContext *s, const TCGArg *args, int opc) break; case 1: if (bswap) { - tcg_out_bswap16(s, COND_AL, TCG_REG_R0, data_reg); + tcg_out_bswap16st(s, COND_AL, TCG_REG_R0, data_reg); tcg_out_st16_8(s, COND_AL, TCG_REG_R0, addr_reg, 0); } else { tcg_out_st16_8(s, COND_AL, data_reg, addr_reg, 0);