- tree decl;
- HOST_WIDE_INT var_size;
-
- /* PR middle-end/14084
- The problem appears when a variable is stored in a larger register
- and later it is used in the original mode or some mode in between
- or some part of variable is accessed.
-
- On little endian machines there is no problem because
- the REG_OFFSET of the start of the variable is the same when
- accessed in any mode (it is 0).
-
- However, this is not true on big endian machines.
- The offset of the start of the variable is different when accessed
- in different modes.
- When we are taking a part of the REG we have to change the OFFSET
- from offset WRT size of mode of REG to offset WRT size of variable.
-
- If we would not do the big endian correction the resulting REG_OFFSET
- would be larger than the size of the DECL.
-
- Examples of correction, for BYTES_BIG_ENDIAN WORDS_BIG_ENDIAN machine:
-
- REG.mode MODE DECL size old offset new offset description
- DI SI 4 4 0 int32 in SImode
- DI SI 1 4 0 char in SImode
- DI QI 1 7 0 char in QImode
- DI QI 4 5 1 1st element in QImode
- of char[4]
- DI HI 4 6 2 1st element in HImode
- of int16[2]
-
- If the size of DECL is equal or greater than the size of REG
- we can't do this correction because the register holds the
- whole variable or a part of the variable and thus the REG_OFFSET
- is already correct. */
-
- decl = REG_EXPR (reg);
- if ((BYTES_BIG_ENDIAN || WORDS_BIG_ENDIAN)
- && decl != NULL
- && offset > 0
- && GET_MODE_SIZE (GET_MODE (reg)) > GET_MODE_SIZE (GET_MODE (new))
- && ((var_size = int_size_in_bytes (TREE_TYPE (decl))) > 0
- && var_size < GET_MODE_SIZE (GET_MODE (reg))))
- {
- int offset_le;
-
- /* Convert machine endian to little endian WRT size of mode of REG. */
- if (WORDS_BIG_ENDIAN)
- offset_le = ((GET_MODE_SIZE (GET_MODE (reg)) - 1 - offset)
- / UNITS_PER_WORD) * UNITS_PER_WORD;
- else
- offset_le = (offset / UNITS_PER_WORD) * UNITS_PER_WORD;
-
- if (BYTES_BIG_ENDIAN)
- offset_le += ((GET_MODE_SIZE (GET_MODE (reg)) - 1 - offset)
- % UNITS_PER_WORD);
- else
- offset_le += offset % UNITS_PER_WORD;
-
- if (offset_le >= var_size)
- {
- /* MODE is wider than the variable so the new reg will cover
- the whole variable so the resulting OFFSET should be 0. */
- offset = 0;
- }
- else
- {
- /* Convert little endian to machine endian WRT size of variable. */
- if (WORDS_BIG_ENDIAN)
- offset = ((var_size - 1 - offset_le)
- / UNITS_PER_WORD) * UNITS_PER_WORD;
- else
- offset = (offset_le / UNITS_PER_WORD) * UNITS_PER_WORD;
-
- if (BYTES_BIG_ENDIAN)
- offset += ((var_size - 1 - offset_le)
- % UNITS_PER_WORD);
- else
- offset += offset_le % UNITS_PER_WORD;
- }
- }
-
- REG_ATTRS (new) = get_reg_attrs (REG_EXPR (reg),