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| author | Richard Sandiford <rsandifo@redhat.com> | 2004-03-18 17:56:12 +0000 |
|---|---|---|
| committer | Richard Sandiford <rsandifo@gcc.gnu.org> | 2004-03-18 17:56:12 +0000 |
| commit | 5da6f16835c04026596f53e9b7d81a99218d2381 (patch) | |
| tree | 05697b0ec31bd950a670489cf27f0b3075ee6055 /gcc | |
| parent | acc63e4c3d942fc6669ee990f0c43b15c41c0592 (diff) | |
| download | gcc-5da6f16835c04026596f53e9b7d81a99218d2381.zip gcc-5da6f16835c04026596f53e9b7d81a99218d2381.tar.gz gcc-5da6f16835c04026596f53e9b7d81a99218d2381.tar.bz2 | |
alias.c (record_set): Detect the case where a register is assigned a new value that has the same base...
* alias.c (record_set): Detect the case where a register is assigned
a new value that has the same base term as the old one.
From-SVN: r79629
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/alias.c | 21 |
2 files changed, 21 insertions, 5 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 94a75a4..60791f0 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2004-03-18 Richard Sandiford <rsandifo@redhat.com> + + * alias.c (record_set): Detect the case where a register is assigned + a new value that has the same base term as the old one. + 2004-03-18 Zdenek Dvorak <rakdver@atrey.karlin.mff.cuni.cz> * doloop.c: Removed. diff --git a/gcc/alias.c b/gcc/alias.c index f317a57..58ec82d 100644 --- a/gcc/alias.c +++ b/gcc/alias.c @@ -993,13 +993,24 @@ record_set (rtx dest, rtx set, void *data ATTRIBUTE_UNUSED) return; } - /* This is not the first set. If the new value is not related to the - old value, forget the base value. Note that the following code is - not detected: - extern int x, y; int *p = &x; p += (&y-&x); + /* If this is not the first set of REGNO, see whether the new value + is related to the old one. There are two cases of interest: + + (1) The register might be assigned an entirely new value + that has the same base term as the original set. + + (2) The set might be a simple self-modification that + cannot change REGNO's base value. + + If neither case holds, reject the original base value as invalid. + Note that the following situation is not detected: + + extern int x, y; int *p = &x; p += (&y-&x); + ANSI C does not allow computing the difference of addresses of distinct top level objects. */ - if (new_reg_base_value[regno]) + if (new_reg_base_value[regno] != 0 + && find_base_value (src) != new_reg_base_value[regno]) switch (GET_CODE (src)) { case LO_SUM: |