diff options
Diffstat (limited to 'tcg/README')
| -rw-r--r-- | tcg/README | 32 |
1 files changed, 25 insertions, 7 deletions
diff --git a/tcg/README b/tcg/README index a550ff176d..34c0775cff 100644 --- a/tcg/README +++ b/tcg/README @@ -314,11 +314,17 @@ This operation would be equivalent to dest = (t1 & ~0x0f00) | ((t2 << 8) & 0x0f00) -* trunc_shr_i32 t0, t1, pos +* extrl_i64_i32 t0, t1 -For 64-bit hosts only, right shift the 64-bit input T1 by POS and -truncate to 32-bit output T0. Depending on the host, this may be -a simple mov/shift, or may require additional canonicalization. +For 64-bit hosts only, extract the low 32-bits of input T1 and place it +into 32-bit output T0. Depending on the host, this may be a simple move, +or may require additional canonicalization. + +* extrh_i64_i32 t0, t1 + +For 64-bit hosts only, extract the high 32-bits of input T1 and place it +into 32-bit output T0. Depending on the host, this may be a simple shift, +or may require additional canonicalization. ********* Conditional moves @@ -466,13 +472,25 @@ On a 32 bit target, all 64 bit operations are converted to 32 bits. A few specific operations must be implemented to allow it (see add2_i32, sub2_i32, brcond2_i32). +On a 64 bit target, the values are transfered between 32 and 64-bit +registers using the following ops: +- trunc_shr_i64_i32 +- ext_i32_i64 +- extu_i32_i64 + +They ensure that the values are correctly truncated or extended when +moved from a 32-bit to a 64-bit register or vice-versa. Note that the +trunc_shr_i64_i32 is an optional op. It is not necessary to implement +it if all the following conditions are met: +- 64-bit registers can hold 32-bit values +- 32-bit values in a 64-bit register do not need to stay zero or + sign extended +- all 32-bit TCG ops ignore the high part of 64-bit registers + Floating point operations are not supported in this version. A previous incarnation of the code generator had full support of them, but it is better to concentrate on integer operations first. -On a 64 bit target, no assumption is made in TCG about the storage of -the 32 bit values in 64 bit registers. - 4.2) Constraints GCC like constraints are used to define the constraints of every |