Added some extra comments to describe what is going on there.
On 13/10/2022 09:14, Richard Biener wrote:
On Wed, 12 Oct 2022, Andre Vieira (lists) wrote:
Hi,
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.
Bootstrappend and regression tested on aarch64-none-linux-gnu and
x86_64-pc-linux-gnu.
+ {
+ tree bf_pos = fold_build2 (MULT_EXPR, bitsizetype,
+ DECL_FIELD_OFFSET (field_decl),
+ build_int_cst (bitsizetype, 8));
+ 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, 8));
+ rep_pos = fold_build2 (PLUS_EXPR, bitsizetype, rep_pos,
+ DECL_FIELD_BIT_OFFSET (rep_decl));
you can use the invariant that DECL_FIELD_OFFSET of rep_decl
and field_decl are always the same. Also please use BITS_PER_UNIT
instead of '8'.
Richard.
diff --git a/gcc/testsuite/gcc.dg/vect/pr107229-1.c
b/gcc/testsuite/gcc.dg/vect/pr107229-1.c
new file mode 100644
index
0000000000000000000000000000000000000000..67b432383d057a630746aa00af50c25fcb527d8e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr107229-1.c
@@ -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;
+}
diff --git a/gcc/testsuite/gcc.dg/vect/pr107229-2.c
b/gcc/testsuite/gcc.dg/vect/pr107229-2.c
new file mode 100644
index
0000000000000000000000000000000000000000..88bffb63d5e8b2d7bcdeae223f4ec6ea4f611bc9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr107229-2.c
@@ -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;
+}
diff --git a/gcc/testsuite/gcc.dg/vect/pr107229-3.c
b/gcc/testsuite/gcc.dg/vect/pr107229-3.c
new file mode 100644
index
0000000000000000000000000000000000000000..4abd8c14531b40e9dbe9802a8f9a0eabba673c9f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr107229-3.c
@@ -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;
+}
diff --git a/gcc/tree-if-conv.cc b/gcc/tree-if-conv.cc
index
e468a4659fa28a3a31c3390cf19bee65f4590b80..01637c5da08d5a2a00a495522fc9a6436a804398
100644
--- a/gcc/tree-if-conv.cc
+++ b/gcc/tree-if-conv.cc
@@ -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;
