The testcase shows that conversions that would impact negatively the
ifcombine field merging implementation won't always have been
optimized out by the time we reach ifcombine.
There's probably room to support multiple conversions with extra
logic, but this workaround should avoid codegen errors until that
logic is figured out.
Regstrapped on x86_64-linux-gnu and on ppc64-linux-gnu, along with 3
other ifcombine patches. Ok to install?
for gcc/ChangeLog
PR tree-optimization/118046
* gimple-fold.cc (decode_field_reference): Don't follow more
than one conversion.
for gcc/testsuite/ChangeLog
PR tree-optimization/118046
* gcc.dg/field-merge-14.c: New.
---
gcc/gimple-fold.cc | 27 +++++++++------------------
gcc/testsuite/gcc.dg/field-merge-14.c | 26 ++++++++++++++++++++++++++
2 files changed, 35 insertions(+), 18 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/field-merge-14.c
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index 92f02ddd77408..06913d57f8aec 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -7554,13 +7554,10 @@ decode_field_reference (tree *pexp, HOST_WIDE_INT
*pbitsize,
narrowing then widening casts, or vice-versa, for those that are not
essential for the compare have already been optimized out at this
point. */
- if (gimple_convert_def_p (exp, res_ops))
+ if (!outer_type && gimple_convert_def_p (exp, res_ops))
{
- if (!outer_type)
- {
- outer_type = TREE_TYPE (exp);
- loc[0] = gimple_location (SSA_NAME_DEF_STMT (exp));
- }
+ outer_type = TREE_TYPE (exp);
+ loc[0] = gimple_location (SSA_NAME_DEF_STMT (exp));
exp = res_ops[0];
}
@@ -7597,13 +7594,10 @@ decode_field_reference (tree *pexp, HOST_WIDE_INT
*pbitsize,
}
/* Another chance to drop conversions. */
- if (gimple_convert_def_p (exp, res_ops))
+ if (!outer_type && gimple_convert_def_p (exp, res_ops))
{
- if (!outer_type)
- {
- outer_type = TREE_TYPE (exp);
- loc[0] = gimple_location (SSA_NAME_DEF_STMT (exp));
- }
+ outer_type = TREE_TYPE (exp);
+ loc[0] = gimple_location (SSA_NAME_DEF_STMT (exp));
exp = res_ops[0];
}
@@ -7623,13 +7617,10 @@ decode_field_reference (tree *pexp, HOST_WIDE_INT
*pbitsize,
/* Yet another chance to drop conversions. This one is allowed to
match a converting load, subsuming the load identification block
below. */
- if (gimple_convert_def_p (exp, res_ops, load))
+ if (!outer_type && gimple_convert_def_p (exp, res_ops, load))
{
- if (!outer_type)
- {
- outer_type = TREE_TYPE (exp);
- loc[0] = gimple_location (SSA_NAME_DEF_STMT (exp));
- }
+ outer_type = TREE_TYPE (exp);
+ loc[0] = gimple_location (SSA_NAME_DEF_STMT (exp));
if (*load)
loc[3] = gimple_location (*load);
exp = res_ops[0];
diff --git a/gcc/testsuite/gcc.dg/field-merge-14.c
b/gcc/testsuite/gcc.dg/field-merge-14.c
new file mode 100644
index 0000000000000..91d84cfebf196
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/field-merge-14.c
@@ -0,0 +1,26 @@
+/* { dg-do run } */
+/* { dg-options "-O -fdump-tree-ifcombine-details" } */
+
+/* Check that we don't get confused by multiple conversions. */
+
+__attribute__((noipa))
+int f(int *a,int *d)
+{
+ signed char b = *a;
+ int c = b;
+ *d = c; // This store is important even if otherwise unused
+ if (c < 0 && (b&1))
+ return 1;
+ return 0;
+}
+
+int main()
+{
+ unsigned char t = 0x81;
+ int x = t, y;
+ int tt = f(&x, &y);
+ if (!tt)
+ __builtin_abort();
+}
+
+/* { dg-final { scan-tree-dump-not "optimizing" "ifcombine" } } */
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
More tolerance and less prejudice are key for inclusion and diversity
Excluding neuro-others for not behaving ""normal"" is *not* inclusive
