diff options
Diffstat (limited to 'gcc/alias.c')
| -rw-r--r-- | gcc/alias.c | 61 |
1 files changed, 59 insertions, 2 deletions
diff --git a/gcc/alias.c b/gcc/alias.c index d69b383..8792da6 100644 --- a/gcc/alias.c +++ b/gcc/alias.c @@ -87,7 +87,7 @@ typedef struct alias_set_entry static int rtx_equal_for_memref_p PARAMS ((rtx, rtx)); static rtx find_symbolic_term PARAMS ((rtx)); -static rtx get_addr PARAMS ((rtx)); +rtx get_addr PARAMS ((rtx)); static int memrefs_conflict_p PARAMS ((int, rtx, int, rtx, HOST_WIDE_INT)); static void record_set PARAMS ((rtx, rtx, void *)); @@ -1340,7 +1340,7 @@ base_alias_check (x, y, x_mode, y_mode) it unchanged unless it is a value; in the latter case we call cselib to get a more useful rtx. */ -static rtx +rtx get_addr (x) rtx x; { @@ -1765,6 +1765,63 @@ true_dependence (mem, mem_mode, x, varies) varies); } +/* Canonical true dependence: X is read after store in MEM takes place. + Variant of true_dependece which assumes MEM has already been + canonicalized (hence we no longer do that here). + The mem_addr argument has been added, since true_dependence computed + this value prior to canonicalizing. */ + +int +canon_true_dependence (mem, mem_mode, mem_addr, x, varies) + rtx mem, mem_addr, x; + enum machine_mode mem_mode; + int (*varies) PARAMS ((rtx, int)); +{ + register rtx x_addr; + + if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) + return 1; + + if (DIFFERENT_ALIAS_SETS_P (x, mem)) + return 0; + + /* If X is an unchanging read, then it can't possibly conflict with any + non-unchanging store. It may conflict with an unchanging write though, + because there may be a single store to this address to initialize it. + Just fall through to the code below to resolve the case where we have + both an unchanging read and an unchanging write. This won't handle all + cases optimally, but the possible performance loss should be + negligible. */ + if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem)) + return 0; + + x_addr = get_addr (XEXP (x, 0)); + + if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode)) + return 0; + + x_addr = canon_rtx (x_addr); + if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr, + SIZE_FOR_MODE (x), x_addr, 0)) + return 0; + + if (aliases_everything_p (x)) + return 1; + + /* We cannot use aliases_everyting_p to test MEM, since we must look + at MEM_MODE, rather than GET_MODE (MEM). */ + if (mem_mode == QImode || GET_CODE (mem_addr) == AND) + return 1; + + /* In true_dependence we also allow BLKmode to alias anything. Why + don't we do this in anti_dependence and output_dependence? */ + if (mem_mode == BLKmode || GET_MODE (x) == BLKmode) + return 1; + + return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr, + varies); +} + /* Returns non-zero if a write to X might alias a previous read from (or, if WRITEP is non-zero, a write to) MEM. */ |