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| author | Jakub Jelinek <jakub@redhat.com> | 2021-06-16 12:17:55 +0200 |
|---|---|---|
| committer | Jakub Jelinek <jakub@redhat.com> | 2021-06-16 12:17:55 +0200 |
| commit | b4b50bf2864e09f028a39a3f460222632c4d7348 (patch) | |
| tree | 158ad7b885e22418c2dac6cabb0002f47d740772 /gcc/stor-layout.c | |
| parent | 43fc4234ad3d9302d3460385b6fdb5e3f59b6986 (diff) | |
| download | gcc-b4b50bf2864e09f028a39a3f460222632c4d7348.zip gcc-b4b50bf2864e09f028a39a3f460222632c4d7348.tar.gz gcc-b4b50bf2864e09f028a39a3f460222632c4d7348.tar.bz2 | |
stor-layout: Create DECL_BIT_FIELD_REPRESENTATIVE even for bitfields in unions [PR101062]
The following testcase is miscompiled on x86_64-linux, the bitfield store
is implemented as a RMW 64-bit operation at d+24 when the d variable has
size of only 28 bytes and scheduling moves in between the R and W part
a store to a different variable that happens to be right after the d
variable.
The reason for this is that we weren't creating
DECL_BIT_FIELD_REPRESENTATIVEs for bitfields in unions.
The following patch does create them, but treats all such bitfields as if
they were in a structure where the particular bitfield is the only field.
2021-06-16 Jakub Jelinek <jakub@redhat.com>
PR middle-end/101062
* stor-layout.c (finish_bitfield_representative): For fields in unions
assume nextf is always NULL.
(finish_bitfield_layout): Compute bit field representatives also in
unions, but handle it as if each bitfield was the only field in the
aggregate.
* gcc.dg/pr101062.c: New test.
Diffstat (limited to 'gcc/stor-layout.c')
| -rw-r--r-- | gcc/stor-layout.c | 26 |
1 files changed, 15 insertions, 11 deletions
diff --git a/gcc/stor-layout.c b/gcc/stor-layout.c index 94b8b21..4e3a41b 100644 --- a/gcc/stor-layout.c +++ b/gcc/stor-layout.c @@ -2072,9 +2072,14 @@ finish_bitfield_representative (tree repr, tree field) bitsize = (bitsize + BITS_PER_UNIT - 1) & ~(BITS_PER_UNIT - 1); /* Now nothing tells us how to pad out bitsize ... */ - nextf = DECL_CHAIN (field); - while (nextf && TREE_CODE (nextf) != FIELD_DECL) - nextf = DECL_CHAIN (nextf); + if (TREE_CODE (DECL_CONTEXT (field)) == RECORD_TYPE) + { + nextf = DECL_CHAIN (field); + while (nextf && TREE_CODE (nextf) != FIELD_DECL) + nextf = DECL_CHAIN (nextf); + } + else + nextf = NULL_TREE; if (nextf) { tree maxsize; @@ -2167,13 +2172,6 @@ finish_bitfield_layout (tree t) tree field, prev; tree repr = NULL_TREE; - /* Unions would be special, for the ease of type-punning optimizations - we could use the underlying type as hint for the representative - if the bitfield would fit and the representative would not exceed - the union in size. */ - if (TREE_CODE (t) != RECORD_TYPE) - return; - for (prev = NULL_TREE, field = TYPE_FIELDS (t); field; field = DECL_CHAIN (field)) { @@ -2233,7 +2231,13 @@ finish_bitfield_layout (tree t) if (repr) DECL_BIT_FIELD_REPRESENTATIVE (field) = repr; - prev = field; + if (TREE_CODE (t) == RECORD_TYPE) + prev = field; + else if (repr) + { + finish_bitfield_representative (repr, field); + repr = NULL_TREE; + } } if (repr) |