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ifcvt: Fix bitpos calculation in bitfield lowering [PR107229]

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The bitposition calculation for the bitfield lowering in loop if conversion was
not taking DECL_FIELD_OFFSET into account, which meant that it would result in
wrong bitpositions for bitfields that did not end up having representations
starting at the beginning of the struct.

gcc/ChangeLog:

	PR tree-optimization/107229
	* tree-if-conv.cc (get_bitfield_rep): Fix bitposition calculation.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/pr107229-1.c: New test.
	* gcc.dg/vect/pr107229-2.c: New test.
	* gcc.dg/vect/pr107229-3.c: New test.
This commit is contained in:
Andre Vieira 2022-10-13 12:09:38 +01:00
parent 6f653a2c85
commit 9f0d4adabe
4 changed files with 81 additions and 4 deletions
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16
gcc/testsuite/gcc.dg/vect/pr107229-1.c Normal file
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@ -0,0 +1,16 @@
/* { dg-do compile } */
/* PR tree-optimization/107229. */
int a, c;
struct {
long d;
int : 8;
int : 27;
int e : 21;
} f;
void g(int b) { a = a & 1; }
int main() {
while (c)
g(f.e);
return 0;
}

18
gcc/testsuite/gcc.dg/vect/pr107229-2.c Normal file
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@ -0,0 +1,18 @@
/* { dg-do compile } */
/* PR tree-optimization/107229. */
int a, c;
struct {
long f;
long g;
long d;
int : 8;
int : 27;
int e : 21;
} f;
void g(int b) { a = a & 1; }
int main() {
while (c)
g(f.e);
return 0;
}

19
gcc/testsuite/gcc.dg/vect/pr107229-3.c Normal file
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@ -0,0 +1,19 @@
/* { dg-do compile } */
/* PR tree-optimization/107229. */
int a, c;
struct {
long f;
long g;
long d;
int : 8;
int : 32;
int : 2;
int e : 21;
} f;
void g(int b) { a = a & 1; }
int main() {
while (c)
g(f.e);
return 0;
}

32
gcc/tree-if-conv.cc
View File

@ -3298,10 +3298,34 @@ get_bitfield_rep (gassign *stmt, bool write, tree *bitpos,
*struct_expr = TREE_OPERAND (comp_ref, 0);
if (bitpos)
*bitpos
= fold_build2 (MINUS_EXPR, bitsizetype,
DECL_FIELD_BIT_OFFSET (field_decl),
DECL_FIELD_BIT_OFFSET (rep_decl));
{
/* To calculate the bitposition of the BITFIELD_REF we have to determine
where our bitfield starts in relation to the container REP_DECL. The
DECL_FIELD_OFFSET of the original bitfield's member FIELD_DECL tells
us how many bytes from the start of the structure there are until the
start of the group of bitfield members the FIELD_DECL belongs to,
whereas DECL_FIELD_BIT_OFFSET will tell us how many bits from that
position our actual bitfield member starts. For the container
REP_DECL adding DECL_FIELD_OFFSET and DECL_FIELD_BIT_OFFSET will tell
us the distance between the start of the structure and the start of
the container, though the first is in bytes and the later other in
bits. With this in mind we calculate the bit position of our new
BITFIELD_REF by subtracting the number of bits between the start of
the structure and the container from the number of bits from the start
of the structure and the actual bitfield member. */
tree bf_pos = fold_build2 (MULT_EXPR, bitsizetype,
DECL_FIELD_OFFSET (field_decl),
build_int_cst (bitsizetype, BITS_PER_UNIT));
bf_pos = fold_build2 (PLUS_EXPR, bitsizetype, bf_pos,
DECL_FIELD_BIT_OFFSET (field_decl));
tree rep_pos = fold_build2 (MULT_EXPR, bitsizetype,
DECL_FIELD_OFFSET (rep_decl),
build_int_cst (bitsizetype, BITS_PER_UNIT));
rep_pos = fold_build2 (PLUS_EXPR, bitsizetype, rep_pos,
DECL_FIELD_BIT_OFFSET (rep_decl));
*bitpos = fold_build2 (MINUS_EXPR, bitsizetype, bf_pos, rep_pos);
}
return rep_decl;