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Use proper term in TCG README

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In TCG, "target" means the host architecture for which TCG generates
the code. Using "guest" rather than "target" to make the document more
consistent.

Signed-off-by: Chen Wei-Ren <chenwj@iis.sinica.edu.tw>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
陳韋任 (Wei-Ren Chen) 2013-03-20 11:42:08 +08:00 committed by Stefan Hajnoczi
parent 8b4a898841
commit 294e4669a5
1 changed files with 9 additions and 5 deletions
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tcg/README
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@ -14,6 +14,10 @@ the emulated architecture. As TCG started as a generic C backend used
for cross compiling, it is assumed that the TCG target is different
from the host, although it is never the case for QEMU.
In this document, we use "guest" to specify what architecture we are
emulating; "target" always means the TCG target, the machine on which
we are running QEMU.
A TCG "function" corresponds to a QEMU Translated Block (TB).
A TCG "temporary" is a variable only live in a basic
@ -379,7 +383,7 @@ double-word product T0. The later is returned in two single-word outputs.
Similar to mulu2, except the two inputs T1 and T2 are signed.
********* 64-bit target on 32-bit host support
********* 64-bit guest on 32-bit host support
The following opcodes are internal to TCG. Thus they are to be implemented by
32-bit host code generators, but are not to be emitted by guest translators.
@ -521,9 +525,9 @@ register.
a better generated code, but it reduces the memory usage of TCG and
the speed of the translation.
- Don't hesitate to use helpers for complicated or seldom used target
- Don't hesitate to use helpers for complicated or seldom used guest
instructions. There is little performance advantage in using TCG to
implement target instructions taking more than about twenty TCG
implement guest instructions taking more than about twenty TCG
instructions. Note that this rule of thumb is more applicable to
helpers doing complex logic or arithmetic, where the C compiler has
scope to do a good job of optimisation; it is less relevant where
@ -531,9 +535,9 @@ register.
inline TCG may still be faster for longer sequences.
- The hard limit on the number of TCG instructions you can generate
per target instruction is set by MAX_OP_PER_INSTR in exec-all.h --
per guest instruction is set by MAX_OP_PER_INSTR in exec-all.h --
you cannot exceed this without risking a buffer overrun.
- Use the 'discard' instruction if you know that TCG won't be able to
prove that a given global is "dead" at a given program point. The
x86 target uses it to improve the condition codes optimisation.
x86 guest uses it to improve the condition codes optimisation.