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| author | pbrook <pbrook@c046a42c-6fe2-441c-8c8c-71466251a162> | 2008-11-04 13:17:17 +0000 |
|---|---|---|
| committer | pbrook <pbrook@c046a42c-6fe2-441c-8c8c-71466251a162> | 2008-11-04 13:17:17 +0000 |
| commit | 0c5f3c8d7d77307d79c6f764ef62ce6ffb3bc9e8 (patch) | |
| tree | ddfdf9a511f31ec8a48cc125ee15798e992bcc97 /tcg/README | |
| parent | 9027db892a56577f2e421091848ef97e59261030 (diff) | |
Mention output overlaps.
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5619 c046a42c-6fe2-441c-8c8c-71466251a162
Diffstat (limited to 'tcg/README')
| -rw-r--r-- | tcg/README | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/tcg/README b/tcg/README index 7e7c06b41c..bdb44dfd3b 100644 --- a/tcg/README +++ b/tcg/README @@ -390,6 +390,11 @@ GCC like constraints are used to define the constraints of every instruction. Memory constraints are not supported in this version. Aliases are specified in the input operands as for GCC. +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. + 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. |