There is a minor inconsistency in the folding behavior within the C
frontend. The C frontend does not currently fold the expression "x",
where x is a const int, yet the FE does fold the expression "x + 0".
This happens because decl_constant_value is called in c_fully_fold only
while recursing over the operands of the expression being folded, i.e.
there is no top-level call to decl_constant_value to handle the case
where the expression being folded happens to be a singular expression
such as "x", as opposed to "x + 5" (where x is a const variable).
To fix this inconsistency, this patch calls decl_constant_value in
c_fully fold after folding the given expression.
Bootstrap + regtest in progress on x86_64-pc-linux-gnu, OK to commit if
testing succeeds?
gcc/c/ChangeLog:
* c-fold.c (c_fully_fold): Call
decl_constant_value_for_optimization after folding
the given expression.
* c-typeck.c (digest_init): Remove redundant call to
decl_constant_value_for_optimization.
gcc/testsuite/ChangeLog:
* gcc.dg/fold-const-1.c: New test.
---
gcc/c/c-fold.c | 1 +
gcc/c/c-typeck.c | 1 -
gcc/testsuite/gcc.dg/fold-const-1.c | 23 +++++++++++++++++++++++
3 files changed, 24 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/fold-const-1.c
diff --git a/gcc/c/c-fold.c b/gcc/c/c-fold.c
index c554e17..ab0b37f 100644
--- a/gcc/c/c-fold.c
+++ b/gcc/c/c-fold.c
@@ -88,6 +88,7 @@ c_fully_fold (tree expr, bool in_init, bool *maybe_const)
}
ret = c_fully_fold_internal (expr, in_init, maybe_const,
&maybe_const_itself, false);
+ ret = decl_constant_value_for_optimization (ret);
if (eptype)
ret = fold_convert_loc (loc, eptype, ret);
*maybe_const &= maybe_const_itself;
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index b691072..4886fc2 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -6791,7 +6791,6 @@ digest_init (location_t init_loc, tree type, tree init,
tree origtype,
inside_init = TREE_OPERAND (inside_init, 0);
}
inside_init = c_fully_fold (inside_init, require_constant, &maybe_const);
- inside_init = decl_constant_value_for_optimization (inside_init);
/* Initialization of an array of chars from a string constant
optionally enclosed in braces. */
diff --git a/gcc/testsuite/gcc.dg/fold-const-1.c
b/gcc/testsuite/gcc.dg/fold-const-1.c
new file mode 100644
index 0000000..9f043b8
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-const-1.c
@@ -0,0 +1,23 @@
+/* { dg-options "-O -fdump-tree-gimple -fdump-tree-ccp1" } */
+
+extern void dummy (const void *);
+
+int
+f1 (void)
+{
+ const int x = 7;
+ dummy (&x);
+ return x;
+}
+
+void foo (int);
+
+void
+f2 (void)
+{
+ const int x = 7;
+ foo (x);
+}
+
+/* { dg-final { scan-tree-dump "foo \\(7\\);" "gimple" } } */
+/* { dg-final { scan-tree-dump-times "return 7;" 2 "ccp1" } } */
--
2.6.3.517.g5b116b4.dirty
