diff options
Diffstat (limited to 'gcc/alias.c')
| -rw-r--r-- | gcc/alias.c | 63 |
1 files changed, 49 insertions, 14 deletions
diff --git a/gcc/alias.c b/gcc/alias.c index 0c6a7442b84..c5e64176313 100644 --- a/gcc/alias.c +++ b/gcc/alias.c @@ -60,14 +60,13 @@ along with GCC; see the file COPYING3. If not see struct Z z2, *pz; - py = &px1.y1; + py = &x1.y1; px2 = &x1; Consider the four questions: Can a store to x1 interfere with px2->y1? Can a store to x1 interfere with px2->z2? - (*px2).z2 Can a store to x1 change the value pointed to by with py? Can a store to x1 change the value pointed to by with pz? @@ -78,24 +77,24 @@ along with GCC; see the file COPYING3. If not see a store through a pointer to an X can overwrite any field that is contained (recursively) in an X (unless we know that px1 != px2). - The last two of the questions can be solved in the same way as the - first two questions but this is too conservative. The observation - is that in some cases analysis we can know if which (if any) fields - are addressed and if those addresses are used in bad ways. This - analysis may be language specific. In C, arbitrary operations may - be applied to pointers. However, there is some indication that - this may be too conservative for some C++ types. + The last two questions can be solved in the same way as the first + two questions but this is too conservative. The observation is + that in some cases we can know which (if any) fields are addressed + and if those addresses are used in bad ways. This analysis may be + language specific. In C, arbitrary operations may be applied to + pointers. However, there is some indication that this may be too + conservative for some C++ types. The pass ipa-type-escape does this analysis for the types whose instances do not escape across the compilation boundary. Historically in GCC, these two problems were combined and a single - data structure was used to represent the solution to these + data structure that was used to represent the solution to these problems. We now have two similar but different data structures, - The data structure to solve the last two question is similar to the - first, but does not contain have the fields in it whose address are - never taken. For types that do escape the compilation unit, the - data structures will have identical information. + The data structure to solve the last two questions is similar to + the first, but does not contain the fields whose address are never + taken. For types that do escape the compilation unit, the data + structures will have identical information. */ /* The alias sets assigned to MEMs assist the back-end in determining @@ -1641,6 +1640,9 @@ find_base_term (rtx x) if (!val) return ret; + if (cselib_sp_based_value_p (val)) + return static_reg_base_value[STACK_POINTER_REGNUM]; + f = val->locs; /* Temporarily reset val->locs to avoid infinite recursion. */ val->locs = NULL; @@ -2760,6 +2762,39 @@ memory_modified_in_insn_p (const_rtx mem, const_rtx insn) return memory_modified; } +/* Return TRUE if the destination of a set is rtx identical to + ITEM. */ +static inline bool +set_dest_equal_p (const_rtx set, const_rtx item) +{ + rtx dest = SET_DEST (set); + return rtx_equal_p (dest, item); +} + +/* Like memory_modified_in_insn_p, but return TRUE if INSN will + *DEFINITELY* modify the memory contents of MEM. */ +bool +memory_must_be_modified_in_insn_p (const_rtx mem, const_rtx insn) +{ + if (!INSN_P (insn)) + return false; + insn = PATTERN (insn); + if (GET_CODE (insn) == SET) + return set_dest_equal_p (insn, mem); + else if (GET_CODE (insn) == PARALLEL) + { + int i; + for (i = 0; i < XVECLEN (insn, 0); i++) + { + rtx sub = XVECEXP (insn, 0, i); + if (GET_CODE (sub) == SET + && set_dest_equal_p (sub, mem)) + return true; + } + } + return false; +} + /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE array. */ |