2) Definitions
+TCG receives RISC-like "TCG ops" and performs some optimizations on them,
+including liveness analysis and trivial constant expression
+evaluation. TCG ops are then implemented in the host CPU back end,
+also known as the TCG "target".
+
The TCG "target" is the architecture for which we generate the
code. It is of course not the same as the "target" of QEMU which is
the emulated architecture. As TCG started as a generic C backend used
t0=t1|~t2
+* clz_i32/i64 t0, t1, t2
+
+t0 = t1 ? clz(t1) : t2
+
+* ctz_i32/i64 t0, t1, t2
+
+t0 = t1 ? ctz(t1) : t2
+
********* Shifts/Rotates
* shl_i32/i64 t0, t1, t2
LEN - the length of the bitfield
POS - the position of the first bit, counting from the LSB
-For example, pos=8, len=4 indicates a 4-bit field at bit 8.
-This operation would be equivalent to
+For example, "deposit_i32 dest, t1, t2, 8, 4" indicates a 4-bit field
+at bit 8. This operation would be equivalent to
dest = (t1 & ~0x0f00) | ((t2 << 8) & 0x0f00)
+* extract_i32/i64 dest, t1, pos, len
+* sextract_i32/i64 dest, t1, pos, len
+
+Extract a bitfield from T1, placing the result in DEST.
+The bitfield is described by POS/LEN, which are immediate values,
+as above for deposit. For extract_*, the result will be extended
+to the left with zeros; for sextract_*, the result will be extended
+to the left with copies of the bitfield sign bit at pos + len - 1.
+
+For example, "sextract_i32 dest, t1, 8, 4" indicates a 4-bit field
+at bit 8. This operation would be equivalent to
+
+ dest = (t1 << 20) >> 28
+
+(using an arithmetic right shift).
+
* extrl_i64_i32 t0, t1
For 64-bit hosts only, extract the low 32-bits of input T1 and place it
Similar to mulu2, except the two inputs T1 and T2 are signed.
+* mulsh_i32/i64 t0, t1, t2
+* muluh_i32/i64 t0, t1, t2
+
+Provide the high part of a signed or unsigned multiply, respectively.
+If mulu2/muls2 are not provided by the backend, the tcg-op generator
+can obtain the same results can be obtained by emitting a pair of
+opcodes, mul+muluh/mulsh.
+
********* Memory Barrier support
* mb <$arg>
The guest translators should generate this opcode for all guest instructions
which have ordering side effects.
-Please see docs/atomics.txt for more information on memory barriers.
+Please see docs/devel/atomics.txt for more information on memory barriers.
********* 64-bit guest on 32-bit host support
instructions. Only indices 0 and 1 are valid and tcg_gen_goto_tb may be issued
at most once with each slot index per TB.
+* lookup_and_goto_ptr tb_addr
+
+Look up a TB address ('tb_addr') and jump to it if valid. If not valid,
+jump to the TCG epilogue to go back to the exec loop.
+
+This operation is optional. If the TCG backend does not implement the
+goto_ptr opcode, emitting this op is equivalent to emitting exit_tb(0).
+
* qemu_ld_i32/i64 t0, t1, flags, memidx
* qemu_st_i32/i64 t0, t1, flags, memidx
For a 32-bit host, qemu_ld/st_i64 is guaranteed to only be used with a
64-bit memory access specified in flags.
+********* Host vector operations
+
+All of the vector ops have two parameters, TCGOP_VECL & TCGOP_VECE.
+The former specifies the length of the vector in log2 64-bit units; the
+later specifies the length of the element (if applicable) in log2 8-bit units.
+E.g. VECL=1 -> 64 << 1 -> v128, and VECE=2 -> 1 << 2 -> i32.
+
+* mov_vec v0, v1
+* ld_vec v0, t1
+* st_vec v0, t1
+
+ Move, load and store.
+
+* dup_vec v0, r1
+
+ Duplicate the low N bits of R1 into VECL/VECE copies across V0.
+
+* dupi_vec v0, c
+
+ Similarly, for a constant.
+ Smaller values will be replicated to host register size by the expanders.
+
+* dup2_vec v0, r1, r2
+
+ Duplicate r2:r1 into VECL/64 copies across V0. This opcode is
+ only present for 32-bit hosts.
+
+* add_vec v0, v1, v2
+
+ v0 = v1 + v2, in elements across the vector.
+
+* sub_vec v0, v1, v2
+
+ Similarly, v0 = v1 - v2.
+
+* mul_vec v0, v1, v2
+
+ Similarly, v0 = v1 * v2.
+
+* neg_vec v0, v1
+
+ Similarly, v0 = -v1.
+
+* and_vec v0, v1, v2
+* or_vec v0, v1, v2
+* xor_vec v0, v1, v2
+* andc_vec v0, v1, v2
+* orc_vec v0, v1, v2
+* not_vec v0, v1
+
+ Similarly, logical operations with and without complement.
+ Note that VECE is unused.
+
+* shli_vec v0, v1, i2
+* shls_vec v0, v1, s2
+
+ Shift all elements from v1 by a scalar i2/s2. I.e.
+
+ for (i = 0; i < VECL/VECE; ++i) {
+ v0[i] = v1[i] << s2;
+ }
+
+* shri_vec v0, v1, i2
+* sari_vec v0, v1, i2
+* shrs_vec v0, v1, s2
+* sars_vec v0, v1, s2
+
+ Similarly for logical and arithmetic right shift.
+
+* shlv_vec v0, v1, v2
+
+ Shift elements from v1 by elements from v2. I.e.
+
+ for (i = 0; i < VECL/VECE; ++i) {
+ v0[i] = v1[i] << v2[i];
+ }
+
+* shrv_vec v0, v1, v2
+* sarv_vec v0, v1, v2
+
+ Similarly for logical and arithmetic right shift.
+
+* cmp_vec v0, v1, v2, cond
+
+ Compare vectors by element, storing -1 for true and 0 for false.
+
*********
Note 1: Some shortcuts are defined when the last operand is known to be
The same register may be used for both an input and an output, even when
they are not explicitly aliased. If an op expands to multiple target
instructions then care must be taken to avoid clobbering input values.
-GCC style "early clobber" outputs are not currently supported.
+GCC style "early clobber" outputs are supported, with '&'.
A target can define specific register or constant constraints. If an
operation uses a constant input constraint which does not allow all
constants, it must also accept registers in order to have a fallback.
+The constraint 'i' is defined generically to accept any constant.
+The constraint 'r' is not defined generically, but is consistently
+used by each backend to indicate all registers.
The movi_i32 and movi_i64 operations must accept any constants.
The mov_i32 and mov_i64 operations must accept any registers of the
same type.
-The ld/st instructions must accept signed 32 bit constant offsets. It
-can be implemented by reserving a specific register to compute the
-address if the offset is too big.
+The ld/st/sti instructions must accept signed 32 bit constant offsets.
+This can be implemented by reserving a specific register in which to
+compute the address if the offset is too big.
The ld/st instructions must accept any destination (ld) or source (st)
register.
+The sti instruction may fail if it cannot store the given constant.
+
4.3) Function call assumptions
- The only supported types for parameters and return value are: 32 and
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