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target/i386: tcg: use cout to commonize add/adc/sub/sbb cases
Use the carry-out vector as the basis to compute AF, CF and OF. The cost is pretty much the same, because the carry-out is just four boolean operations, and the code is much smaller because add/adc/sub/sbb now share most of it. A similar algorithm to what is used in target/i386/emulate can also be used for APX, in order to build the result of CCMP/CTEST with a new CC_OP_*. CCMP needs to place into the flags from either a subtraction or a constant value; CTEST likewise place into the flags either an AND or a constant value. The new CC_OP for CCMP and CTEST would store for a successful predcate: - in DST and SRC2, the result of the operation; - in SRC, a carry-out vector for CCMP or zero for CTEST; If the default flag value is used, DST/SRC/SRC2 can be filled with constants: - in DST the negated ZF; - in SRC's top 2 bits, a value that results in the desired OF and CF; - in SRC2 a suitable value (any of 0/1/~0/~1) that can be used instead of DST to compute the desired SF and PF. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini
parent
767149d3d0
commit
5dcdbd0712
3 changed files with 52 additions and 78 deletions
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@ -2843,4 +2843,29 @@ static inline bool ctl_has_irq(CPUX86State *env)
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# define TARGET_VSYSCALL_PAGE (UINT64_C(-10) << 20)
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#endif
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/* majority(NOT a, b, c) = (a ^ b) ? b : c */
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#define MAJ_INV1(a, b, c) ((((a) ^ (b)) & ((b) ^ (c))) ^ (c))
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/*
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* ADD_COUT_VEC(x, y) = majority((x + y) ^ x ^ y, x, y)
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*
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* If two corresponding bits in x and y are the same, that's the carry
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* independent of the value (x+y)^x^y. Hence x^y can be replaced with
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* 1 in (x+y)^x^y, resulting in majority(NOT (x+y), x, y)
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*/
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#define ADD_COUT_VEC(op1, op2, result) \
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MAJ_INV1(result, op1, op2)
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/*
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* SUB_COUT_VEC(x, y) = NOT majority(x, NOT y, (x - y) ^ x ^ NOT y)
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* = majority(NOT x, y, (x - y) ^ x ^ y)
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*
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* Note that the carry out is actually a borrow, i.e. it is inverted.
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* If two corresponding bits in x and y are different, the value of the
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* bit in (x-y)^x^y likewise does not matter. Hence, x^y can be replaced
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* with 0 in (x-y)^x^y, resulting in majority(NOT x, y, x-y)
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*/
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#define SUB_COUT_VEC(op1, op2, result) \
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MAJ_INV1(op1, op2, result)
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#endif /* I386_CPU_H */
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@ -45,31 +45,6 @@
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#define LF_MASK_CF (0x01 << LF_BIT_CF)
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#define LF_MASK_PO (0x01 << LF_BIT_PO)
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/* majority(NOT a, b, c) = (a ^ b) ? b : c */
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#define MAJ_INV1(a, b, c) ((((a) ^ (b)) & ((b) ^ (c))) ^ (c))
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/*
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* ADD_COUT_VEC(x, y) = majority((x + y) ^ x ^ y, x, y)
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*
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* If two corresponding bits in x and y are the same, that's the carry
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* independent of the value (x+y)^x^y. Hence x^y can be replaced with
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* 1 in (x+y)^x^y, resulting in majority(NOT (x+y), x, y)
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*/
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#define ADD_COUT_VEC(op1, op2, result) \
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MAJ_INV1(result, op1, op2)
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/*
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* SUB_COUT_VEC(x, y) = NOT majority(x, NOT y, (x - y) ^ x ^ NOT y)
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* = majority(NOT x, y, (x - y) ^ x ^ y)
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*
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* Note that the carry out is actually a borrow, i.e. it is inverted.
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* If two corresponding bits in x and y are different, the value of the
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* bit in (x-y)^x^y likewise does not matter. Hence, x^y can be replaced
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* with 0 in (x-y)^x^y, resulting in majority(NOT x, y, x-y)
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*/
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#define SUB_COUT_VEC(op1, op2, result) \
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MAJ_INV1(op1, op2, result)
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/* ******************* */
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/* OSZAPC */
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/* ******************* */
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@ -44,18 +44,32 @@
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/* dynamic flags computation */
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static uint32_t glue(compute_all_add, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1)
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static uint32_t glue(compute_all_cout, SUFFIX)(DATA_TYPE dst, DATA_TYPE carries)
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{
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uint32_t cf, pf, af, zf, sf, of;
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DATA_TYPE src2 = dst - src1;
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uint32_t af_cf, pf, zf, sf, of;
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cf = dst < src1;
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/* PF, ZF, SF computed from result. */
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pf = compute_pf(dst);
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af = (dst ^ src1 ^ src2) & CC_A;
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zf = (dst == 0) * CC_Z;
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sf = lshift(dst, 8 - DATA_BITS) & CC_S;
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of = lshift((src1 ^ src2 ^ -1) & (src1 ^ dst), 12 - DATA_BITS) & CC_O;
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return cf + pf + af + zf + sf + of;
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/*
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* AF, CF, OF computed from carry out vector. To compute AF and CF, rotate it
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* left by one so cout(DATA_BITS - 1) is in bit 0 and cout(3) in bit 4.
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*
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* To compute OF, place the highest two carry bits into OF and the bit
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* immediately to the right of it; then, adding CC_O / 2 XORs them.
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*/
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af_cf = ((carries << 1) | (carries >> (DATA_BITS - 1))) & (CC_A | CC_C);
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of = (lshift(carries, 12 - DATA_BITS) + CC_O / 2) & CC_O;
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return pf + zf + sf + af_cf + of;
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}
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static uint32_t glue(compute_all_add, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1)
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{
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DATA_TYPE src2 = dst - src1;
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DATA_TYPE carries = ADD_COUT_VEC(src1, src2, dst);
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return glue(compute_all_cout, SUFFIX)(dst, carries);
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}
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static int glue(compute_c_add, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1)
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@ -66,25 +80,9 @@ static int glue(compute_c_add, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1)
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static uint32_t glue(compute_all_adc, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1,
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DATA_TYPE src3)
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{
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uint32_t cf, pf, af, zf, sf, of;
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#ifdef WIDER_TYPE
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WIDER_TYPE src13 = (WIDER_TYPE) src1 + (WIDER_TYPE) src3;
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DATA_TYPE src2 = dst - src13;
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cf = dst < src13;
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#else
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DATA_TYPE src2 = dst - src1 - src3;
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cf = (src3 ? dst <= src1 : dst < src1);
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#endif
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pf = compute_pf(dst);
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af = (dst ^ src1 ^ src2) & 0x10;
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zf = (dst == 0) << 6;
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sf = lshift(dst, 8 - DATA_BITS) & 0x80;
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of = lshift((src1 ^ src2 ^ -1) & (src1 ^ dst), 12 - DATA_BITS) & CC_O;
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return cf + pf + af + zf + sf + of;
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DATA_TYPE carries = ADD_COUT_VEC(src1, src2, dst);
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return glue(compute_all_cout, SUFFIX)(dst, carries);
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}
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static int glue(compute_c_adc, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1,
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@ -101,16 +99,9 @@ static int glue(compute_c_adc, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1,
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static uint32_t glue(compute_all_sub, SUFFIX)(DATA_TYPE dst, DATA_TYPE src2)
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{
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uint32_t cf, pf, af, zf, sf, of;
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DATA_TYPE src1 = dst + src2;
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cf = src1 < src2;
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pf = compute_pf(dst);
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af = (dst ^ src1 ^ src2) & CC_A;
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zf = (dst == 0) * CC_Z;
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sf = lshift(dst, 8 - DATA_BITS) & CC_S;
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of = lshift((src1 ^ src2) & (src1 ^ dst), 12 - DATA_BITS) & CC_O;
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return cf + pf + af + zf + sf + of;
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DATA_TYPE carries = SUB_COUT_VEC(src1, src2, dst);
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return glue(compute_all_cout, SUFFIX)(dst, carries);
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}
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static int glue(compute_c_sub, SUFFIX)(DATA_TYPE dst, DATA_TYPE src2)
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@ -123,25 +114,9 @@ static int glue(compute_c_sub, SUFFIX)(DATA_TYPE dst, DATA_TYPE src2)
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static uint32_t glue(compute_all_sbb, SUFFIX)(DATA_TYPE dst, DATA_TYPE src2,
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DATA_TYPE src3)
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{
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uint32_t cf, pf, af, zf, sf, of;
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#ifdef WIDER_TYPE
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WIDER_TYPE src23 = (WIDER_TYPE) src2 + (WIDER_TYPE) src3;
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DATA_TYPE src1 = dst + src23;
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cf = src1 < src23;
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#else
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DATA_TYPE src1 = dst + src2 + src3;
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cf = (src3 ? src1 <= src2 : src1 < src2);
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#endif
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pf = compute_pf(dst);
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af = (dst ^ src1 ^ src2) & 0x10;
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zf = (dst == 0) << 6;
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sf = lshift(dst, 8 - DATA_BITS) & 0x80;
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of = lshift((src1 ^ src2) & (src1 ^ dst), 12 - DATA_BITS) & CC_O;
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return cf + pf + af + zf + sf + of;
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DATA_TYPE carries = SUB_COUT_VEC(src1, src2, dst);
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return glue(compute_all_cout, SUFFIX)(dst, carries);
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}
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static int glue(compute_c_sbb, SUFFIX)(DATA_TYPE dst, DATA_TYPE src2,
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@ -286,6 +261,5 @@ static int glue(compute_c_blsi, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1)
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#undef DATA_BITS
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#undef SIGN_MASK
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#undef DATA_TYPE
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#undef DATA_MASK
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#undef SUFFIX
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#undef WIDER_TYPE
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