Per Richi's suggestions I tweaked the recent tree-ssa-dom.c equivalence
code to use int_fits_type_p rather than creating a new integer node and
verifying it had the same value as the old node.
At the time I dropped the TYPE_PRECISION check as I thought it was
redundant with the int_fits_type_p tests. However int_fits_type_p only
checks for a widening precision if it can't prove the constant fits
within the bounds of the new type.
Thus we could record an equivalence after a narrowing conversion, which
is wrong in this particular case.
Fixed by adding the TYPE_PRECISION checks back.
Bootstrapped & regression tested on x86_64-unknown-linux-gnu. Installed.
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1e25a82..a3b60c9 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2013-04-03 Jeff Law <l...@redhat.com>
+
+ PR tree-optimization/56799
+ * tree-ssa-dom.c (record_equivalences_from_incoming_edge): Bring
+ back test for widening conversion erroneously dropped in prior
+ change.
+
2013-04-03 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
PR target/56809
@@ -896,6 +903,7 @@
* config/tilegx/tilepro.h (PROFILE_BEFORE_PROLOGUE): Define.
2013-03-25 Jeff Law <l...@redhat.com>
+
* tree-ssa-dom.c (record_equivalences_from_incoming_edge): Add missing
check for INTEGRAL_TYPE_P that was missing due to checking in
wrong version of prior patch.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 2cc5fa8..dc0b745 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2013-04-03 Jeff Law <l...@redhat.com>
+
+ PR tree-optimization/56799
+ * gcc.c-torture/execute/pr56799.c: New test.
+
2013-04-03 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/56815
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr56799.c
b/gcc/testsuite/gcc.c-torture/execute/pr56799.c
new file mode 100644
index 0000000..d9ee26b
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr56799.c
@@ -0,0 +1,43 @@
+
+#include <stdio.h>
+typedef struct { int x; int y;} S;
+extern int foo(S*);
+int hi = 0, lo = 0;
+
+int main()
+{
+ S a;
+ int r;
+ a.x = (int) 0x00010000;
+ a.y = 1;
+ r = foo (&a);
+ if (r == 2 && lo==0 && hi==1)
+ {
+ exit (0);
+ }
+ abort ();
+}
+
+typedef unsigned short u16;
+
+__attribute__ ((noinline)) int foo (S* ptr)
+{
+ int a = ptr->x;
+ int c = 0;
+ u16 b = (u16) a;
+ if (b != 0)
+ {
+ lo = 1;
+ c += ptr->y;
+ }
+ b = a >> 16;
+ if (b != 0)
+ {
+ hi = 1;
+ c+= ptr->y;
+ }
+ c += ptr->y;
+ return c;
+}
+
+
diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index 29d2bb4..d98a646 100644
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -1151,9 +1151,15 @@ record_equivalences_from_incoming_edge (basic_block bb)
{
tree old_rhs = gimple_assign_rhs1 (defstmt);
- /* If the constant is in the range of the type of OLD_RHS,
- then convert the constant and record the equivalence. */
+ /* If the conversion widens the original value and
+ the constant is in the range of the type of OLD_RHS,
+ then convert the constant and record the equivalence.
+
+ Note that int_fits_type_p does not check the precision
+ if the upper and lower bounds are OK. */
if (INTEGRAL_TYPE_P (TREE_TYPE (old_rhs))
+ && (TYPE_PRECISION (TREE_TYPE (lhs))
+ > TYPE_PRECISION (TREE_TYPE (old_rhs)))
&& int_fits_type_p (rhs, TREE_TYPE (old_rhs)))
{
tree newval = fold_convert (TREE_TYPE (old_rhs), rhs);
