diff options
Diffstat (limited to 'gcc/ada/exp_util.ads')
| -rw-r--r-- | gcc/ada/exp_util.ads | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/gcc/ada/exp_util.ads b/gcc/ada/exp_util.ads index e45930d..8dc14b7 100644 --- a/gcc/ada/exp_util.ads +++ b/gcc/ada/exp_util.ads @@ -208,6 +208,36 @@ package Exp_Util is -- computes the image without using concatenation, and one for the -- variable that holds the result. + function Component_May_Be_Bit_Aligned (Comp : Entity_Id) return Boolean; + -- This function is in charge of detecting record components that may + -- cause trouble in the back end if an attempt is made to assign the + -- component. The back end can handle such assignments with no problem + -- if the components involved are small (64-bits or less) records or + -- scalar items (including bit-packed arrays represented with modular + -- types) or are both aligned on a byte boundary (starting on a byte + -- boundary, and occupying an integral number of bytes). + -- + -- However, problems arise for records larger than 64 bits, or for + -- arrays (other than bit-packed arrays represented with a modular + -- type) if the component starts on a non-byte boundary, or does + -- not occupy an integral number of bytes (i.e. there are some bits + -- possibly shared with fields at the start or beginning of the + -- component). The back end cannot handle loading and storing such + -- components in a single operation. + -- + -- This function is used to detect the troublesome situation. it is + -- conservative in the sense that it produces True unless it knows + -- for sure that the component is safe (as outlined in the first + -- paragraph above). The code generation for record and array + -- assignment checks for trouble using this function, and if so + -- the assignment is generated component-wise, which the back end + -- is required to handle correctly. + -- + -- Note that in GNAT 3, the back end will reject such components + -- anyway, so the hard work in checking for this case is wasted + -- in GNAT 3, but it's harmless, so it is easier to do it in + -- all cases, rather than conditionalize it in GNAT 5 or beyond. + procedure Convert_To_Actual_Subtype (Exp : Node_Id); -- The Etype of an expression is the nominal type of the expression, -- not the actual subtype. Often these are the same, but not always. @@ -512,6 +542,14 @@ package Exp_Util is -- operand and result types. This is called in package Exp_Fixd to -- determine whether to expand such operations. + function Type_May_Have_Bit_Aligned_Components + (Typ : Entity_Id) return Boolean; + -- Determines if Typ is a composite type that has within it (looking + -- down recursively at any subcomponents), a record type which has a + -- component that may be bit aligned (see Possible_Bit_Aligned_Component). + -- The result is conservative, in that a result of False is decisive. + -- A result of True means that such a component may or may not be present. + procedure Wrap_Cleanup_Procedure (N : Node_Id); -- Given an N_Subprogram_Body node, this procedure adds an Abort_Defer -- call at the start of the statement sequence, and an Abort_Undefer call |