diff mbox series

ifcvt: Fix bitpos calculation in bitfield lowering [PR107229]

Message ID f84887dd-1d9e-e53f-b171-494426634026@arm.com
State New
Headers
Series ifcvt: Fix bitpos calculation in bitfield lowering [PR107229] |

Commit Message

Andre Vieira (lists) Oct. 12, 2022, 5:29 p.m. UTC 
  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.

gcc/ChangeLog:

     PR tree-optimization/107229
     * gcc/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.

Comments

Richard Biener Oct. 13, 2022, 8:14 a.m. UTC | #1 
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.
Rainer Orth Oct. 13, 2022, 11:39 a.m. UTC | #2 
Hi Andre,

> 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.

I tried this patch together with the one for PR tree-optimization/107226
on sparc-sun-solaris2.11 to check if it cures the bootstrap failure
reported in PR tree-optimization/107232.  While this restores bootstrap,
several of the new tests FAIL:

+FAIL: gcc.dg/vect/vect-bitfield-read-1.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-read-1.c scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-read-2.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-read-2.c scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-read-3.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 2 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-read-3.c scan-tree-dump-times vect "vectorized 2 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-read-4.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-read-4.c scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-read-6.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-write-1.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-write-1.c scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-write-2.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-write-2.c scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-write-3.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-write-3.c scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-write-5.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
+FAIL: gcc.dg/vect/vect-bitfield-write-5.c scan-tree-dump-times vect "vectorized 1 loops" 1

For vect-bitfield-read-1.c, the dump has

gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   ==> examining pattern def statement: patt_31 = patt_30 >> 1;
gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   ==> examining statement: patt_31 = patt_30 >> 1;
gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use: operand _ifc__27 & 4294967294, type of def: internal
gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use: vectype vector(2) unsigned int
gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use: operand 1, type of def: constant
gcc.dg/vect/vect-bitfield-read-1.c:25:23: missed:   op not supported by target.
gcc.dg/vect/vect-bitfield-read-1.c:23:1: missed:   not vectorized: relevant stmt not supported: patt_31 = patt_30 >> 1;
gcc.dg/vect/vect-bitfield-read-1.c:25:23: missed:  bad operation or unsupported loop bound.
gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:  ***** Analysis  failed with vector mode V2SI

	Rainer
Andre Vieira (lists) Oct. 13, 2022, 1:55 p.m. UTC | #3 
Hi Rainer,

Thanks for reporting, I was actually expecting these! I thought about 
pre-empting them by using a positive filter on the tests for aarch64 and 
x86_64 as I knew those would pass, but I thought it would be better to 
let other targets report failures since then you get a testsuite that 
covers more targets than just what I'm able to check.

Are there any sparc architectures that would support these or should I 
just xfail sparc*-*-* ?

For instance: I also saw PR107240 for which one of the write tests fails 
on Power 7 BE. I'm suggesting adding an xfail for that one

Kind regards,
Andre

On 13/10/2022 12:39, Rainer Orth wrote:
> Hi Andre,
>
>> 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.
> I tried this patch together with the one for PR tree-optimization/107226
> on sparc-sun-solaris2.11 to check if it cures the bootstrap failure
> reported in PR tree-optimization/107232.  While this restores bootstrap,
> several of the new tests FAIL:
>
> +FAIL: gcc.dg/vect/vect-bitfield-read-1.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-read-1.c scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-read-2.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-read-2.c scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-read-3.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 2 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-read-3.c scan-tree-dump-times vect "vectorized 2 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-read-4.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-read-4.c scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-read-6.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-write-1.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-write-1.c scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-write-2.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-write-2.c scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-write-3.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-write-3.c scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-write-5.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 1
> +FAIL: gcc.dg/vect/vect-bitfield-write-5.c scan-tree-dump-times vect "vectorized 1 loops" 1
>
> For vect-bitfield-read-1.c, the dump has
>
> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   ==> examining pattern def statement: patt_31 = patt_30 >> 1;
> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   ==> examining statement: patt_31 = patt_30 >> 1;
> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use: operand _ifc__27 & 4294967294, type of def: internal
> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use: vectype vector(2) unsigned int
> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use: operand 1, type of def: constant
> gcc.dg/vect/vect-bitfield-read-1.c:25:23: missed:   op not supported by target.
> gcc.dg/vect/vect-bitfield-read-1.c:23:1: missed:   not vectorized: relevant stmt not supported: patt_31 = patt_30 >> 1;
> gcc.dg/vect/vect-bitfield-read-1.c:25:23: missed:  bad operation or unsupported loop bound.
> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:  ***** Analysis  failed with vector mode V2SI
>
> 	Rainer
>
Richard Biener Oct. 13, 2022, 2:15 p.m. UTC | #4 
On Thu, 13 Oct 2022, Andre Vieira (lists) wrote:

> Hi Rainer,
> 
> Thanks for reporting, I was actually expecting these! I thought about
> pre-empting them by using a positive filter on the tests for aarch64 and
> x86_64 as I knew those would pass, but I thought it would be better to let
> other targets report failures since then you get a testsuite that covers more
> targets than just what I'm able to check.
> 
> Are there any sparc architectures that would support these or should I just
> xfail sparc*-*-* ?
> 
> For instance: I also saw PR107240 for which one of the write tests fails on
> Power 7 BE. I'm suggesting adding an xfail for that one

for the failure below we seem to require vectorizing shifts for which I
think we have a vect_* target to check?

> Kind regards,
> Andre
> 
> On 13/10/2022 12:39, Rainer Orth wrote:
> > Hi Andre,
> >
> >> 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.
> > I tried this patch together with the one for PR tree-optimization/107226
> > on sparc-sun-solaris2.11 to check if it cures the bootstrap failure
> > reported in PR tree-optimization/107232.  While this restores bootstrap,
> > several of the new tests FAIL:
> >
> > +FAIL: gcc.dg/vect/vect-bitfield-read-1.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-read-1.c scan-tree-dump-times vect
> > "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-read-2.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-read-2.c scan-tree-dump-times vect
> > "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-read-3.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "vectorized 2 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-read-3.c scan-tree-dump-times vect
> > "vectorized 2 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-read-4.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-read-4.c scan-tree-dump-times vect
> > "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-read-6.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-write-1.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-write-1.c scan-tree-dump-times vect
> > "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-write-2.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-write-2.c scan-tree-dump-times vect
> > "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-write-3.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-write-3.c scan-tree-dump-times vect
> > "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-write-5.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "vectorized 1 loops" 1
> > +FAIL: gcc.dg/vect/vect-bitfield-write-5.c scan-tree-dump-times vect
> > "vectorized 1 loops" 1
> >
> > For vect-bitfield-read-1.c, the dump has
> >
> > gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   ==> examining pattern def
> > statement: patt_31 = patt_30 >> 1;
> > gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   ==> examining statement:
> > patt_31 = patt_30 >> 1;
> > gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use:
> > operand _ifc__27 & 4294967294, type of def: internal
> > gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use:
> > vectype vector(2) unsigned int
> > gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use:
> > operand 1, type of def: constant
> > gcc.dg/vect/vect-bitfield-read-1.c:25:23: missed:   op not supported by
> > target.
> > gcc.dg/vect/vect-bitfield-read-1.c:23:1: missed:   not vectorized: relevant
> > stmt not supported: patt_31 = patt_30 >> 1;
> > gcc.dg/vect/vect-bitfield-read-1.c:25:23: missed:  bad operation or
> > unsupported loop bound.
> > gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:  ***** Analysis  failed with
> > vector mode V2SI
> >
> >  Rainer
> >
>
Andre Vieira (lists) Oct. 13, 2022, 2:42 p.m. UTC | #5 
On 13/10/2022 15:15, Richard Biener wrote:
> On Thu, 13 Oct 2022, Andre Vieira (lists) wrote:
>
>> Hi Rainer,
>>
>> Thanks for reporting, I was actually expecting these! I thought about
>> pre-empting them by using a positive filter on the tests for aarch64 and
>> x86_64 as I knew those would pass, but I thought it would be better to let
>> other targets report failures since then you get a testsuite that covers more
>> targets than just what I'm able to check.
>>
>> Are there any sparc architectures that would support these or should I just
>> xfail sparc*-*-* ?
>>
>> For instance: I also saw PR107240 for which one of the write tests fails on
>> Power 7 BE. I'm suggesting adding an xfail for that one
> for the failure below we seem to require vectorizing shifts for which I
> think we have a vect_* target to check?
'vect_shift' no sparc on the list of supported targets, so that should 
do it, I'll add it when I add my fix for powerpc too.
>
>> Kind regards,
>> Andre
>>
>> On 13/10/2022 12:39, Rainer Orth wrote:
>>> Hi Andre,
>>>
>>>> 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.
>>> I tried this patch together with the one for PR tree-optimization/107226
>>> on sparc-sun-solaris2.11 to check if it cures the bootstrap failure
>>> reported in PR tree-optimization/107232.  While this restores bootstrap,
>>> several of the new tests FAIL:
>>>
>>> +FAIL: gcc.dg/vect/vect-bitfield-read-1.c -flto -ffat-lto-objects
>>> scan-tree-dump-times vect "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-read-1.c scan-tree-dump-times vect
>>> "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-read-2.c -flto -ffat-lto-objects
>>> scan-tree-dump-times vect "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-read-2.c scan-tree-dump-times vect
>>> "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-read-3.c -flto -ffat-lto-objects
>>> scan-tree-dump-times vect "vectorized 2 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-read-3.c scan-tree-dump-times vect
>>> "vectorized 2 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-read-4.c -flto -ffat-lto-objects
>>> scan-tree-dump-times vect "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-read-4.c scan-tree-dump-times vect
>>> "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-read-6.c -flto -ffat-lto-objects
>>> scan-tree-dump-times vect "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-write-1.c -flto -ffat-lto-objects
>>> scan-tree-dump-times vect "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-write-1.c scan-tree-dump-times vect
>>> "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-write-2.c -flto -ffat-lto-objects
>>> scan-tree-dump-times vect "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-write-2.c scan-tree-dump-times vect
>>> "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-write-3.c -flto -ffat-lto-objects
>>> scan-tree-dump-times vect "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-write-3.c scan-tree-dump-times vect
>>> "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-write-5.c -flto -ffat-lto-objects
>>> scan-tree-dump-times vect "vectorized 1 loops" 1
>>> +FAIL: gcc.dg/vect/vect-bitfield-write-5.c scan-tree-dump-times vect
>>> "vectorized 1 loops" 1
>>>
>>> For vect-bitfield-read-1.c, the dump has
>>>
>>> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   ==> examining pattern def
>>> statement: patt_31 = patt_30 >> 1;
>>> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   ==> examining statement:
>>> patt_31 = patt_30 >> 1;
>>> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use:
>>> operand _ifc__27 & 4294967294, type of def: internal
>>> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use:
>>> vectype vector(2) unsigned int
>>> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:   vect_is_simple_use:
>>> operand 1, type of def: constant
>>> gcc.dg/vect/vect-bitfield-read-1.c:25:23: missed:   op not supported by
>>> target.
>>> gcc.dg/vect/vect-bitfield-read-1.c:23:1: missed:   not vectorized: relevant
>>> stmt not supported: patt_31 = patt_30 >> 1;
>>> gcc.dg/vect/vect-bitfield-read-1.c:25:23: missed:  bad operation or
>>> unsupported loop bound.
>>> gcc.dg/vect/vect-bitfield-read-1.c:25:23: note:  ***** Analysis  failed with
>>> vector mode V2SI
>>>
>>>   Rainer
>>>
diff mbox series

Patch

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..33160ddef80cbd75c2a927fb50bddd792bbf5dd4 100644
--- a/gcc/tree-if-conv.cc
+++ b/gcc/tree-if-conv.cc
@@ -3298,10 +3298,20 @@  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));
+    {
+      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));
+
+      *bitpos = fold_build2 (MINUS_EXPR, bitsizetype, bf_pos, rep_pos);
+    }
 
   return rep_decl;