lower-bitint: Fix _BitInt .{ADD,SUB}_OVERFLOW lowering [PR112750]

The .{ADD,SUB}_OVERFLOW lowering is implemented by performing normal
addition/subtraction (perhaps extended to even more bits than normally by
continuing with extended values of operands after running of normal bits)
and in addition to that trying to compute if certain sets of bits are either
all zero or all sign extensions of the least significant bit.

That code is in a lot of cases guarded just by a single condition (which
can be idx > startlimb, idx >= startlimb or idx == startlimb) or by
2 conditions - if (idx >= startlimb) { if (idx == startlimb) ... else ... }
Now, if_then_if_then_else when the second argument is NULL works just as
if_then and sets m_gsi to be within the initially empty then block and that is
where we emit code for constant tidx startlimb + (cmp_code == GT_EXPR).
But in the 2 conditions case, m_gsi is set to the initially empty else
block, so using EQ_EXPR for the condition was incorrect (and strangely
nothing in the testsuite caught that), because the code for extracting the
lowest set of bits (i.e. when tidx is startlimb) is then done when idx
is not startlimb rather than when it is.
The following patch fixes that.

Note, when developing the lowering, I was using gcov to make sure all code
is covered by the testsuite with minimum exceptions, so no idea how this
slipped out.

2023-12-01  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/112750
	* gimple-lower-bitint.cc (bitint_large_huge::lower_addsub_overflow):
	Use NE_EXPR rather than EQ_EXPR for g2 if !single_comparison and
	adjust probabilities.

	* gcc.dg/bitint-41.c: Use -std=c23 rather than -std=c2x.
	* gcc.dg/torture/bitint-43.c: Likewise.
	* gcc.dg/torture/bitint-44.c: Likewise.
	* gcc.dg/torture/bitint-45.c: New test.

diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc
index 5024815ed9dfae31b295e48e1380990a7caa63eb..09eb7a34e91b6b9a71d0d0f2171708af58fc7efc 100644 (file)
--- a/gcc/gimple-lower-bitint.cc
+++ b/gcc/gimple-lower-bitint.cc
@@ -4028,11 +4028,11 @@ bitint_large_huge::lower_addsub_overflow (tree obj, gimple *stmt)
                  edge edge_true_true, edge_true_false, edge_false;
                  gimple *g2 = NULL;
                  if (!single_comparison)
-                   g2 = gimple_build_cond (EQ_EXPR, idx,
+                   g2 = gimple_build_cond (NE_EXPR, idx,
                                            size_int (startlimb), NULL_TREE,
                                            NULL_TREE);
                  if_then_if_then_else (g, g2, profile_probability::likely (),
-                                       profile_probability::unlikely (),
+                                       profile_probability::likely (),
                                        edge_true_true, edge_true_false,
                                        edge_false);
                  unsigned tidx = startlimb + (cmp_code == GT_EXPR);

diff --git a/gcc/testsuite/gcc.dg/bitint-41.c b/gcc/testsuite/gcc.dg/bitint-41.c
index d87ea08bdf6497a49e0b7beb4826db0804f9c449..f97f03cd091c44ca14b0ef490c7961b9f9f260d3 100644 (file)
--- a/gcc/testsuite/gcc.dg/bitint-41.c
+++ b/gcc/testsuite/gcc.dg/bitint-41.c
@@ -1,6 +1,6 @@
 /* PR middle-end/112336 */
 /* { dg-do compile { target bitint } } */
-/* { dg-options "-std=c2x" } */
+/* { dg-options "-std=c23" } */
 
 unsigned _BitInt(1) v1;
 unsigned _BitInt(1) *p1 = &v1;

diff --git a/gcc/testsuite/gcc.dg/torture/bitint-43.c b/gcc/testsuite/gcc.dg/torture/bitint-43.c
index 4265bffef7066fa2f34d0209b2d85c73f94a492b..a45f5c6b493ba3c49e7b4c104522a4194da14044 100644 (file)
--- a/gcc/testsuite/gcc.dg/torture/bitint-43.c
+++ b/gcc/testsuite/gcc.dg/torture/bitint-43.c
@@ -1,6 +1,6 @@
 /* PR c/111309 */
 /* { dg-do run { target bitint } } */
-/* { dg-options "-std=c2x -pedantic-errors" } */
+/* { dg-options "-std=c23 -pedantic-errors" } */
 /* { dg-skip-if "" { ! run_expensive_tests }  { "*" } { "-O0" "-O2" } } */
 /* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
 

diff --git a/gcc/testsuite/gcc.dg/torture/bitint-44.c b/gcc/testsuite/gcc.dg/torture/bitint-44.c
index 938c0e917f344223dcdae281219d4dd12d814eca..fe5c168538781a15ef9200e53a2b2e1395ab1a62 100644 (file)
--- a/gcc/testsuite/gcc.dg/torture/bitint-44.c
+++ b/gcc/testsuite/gcc.dg/torture/bitint-44.c
@@ -1,6 +1,6 @@
 /* PR c/111309 */
 /* { dg-do run { target bitint } } */
-/* { dg-options "-std=c2x -pedantic-errors" } */
+/* { dg-options "-std=c23 -pedantic-errors" } */
 /* { dg-skip-if "" { ! run_expensive_tests }  { "*" } { "-O0" "-O2" } } */
 /* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
 

diff --git a/gcc/testsuite/gcc.dg/torture/bitint-45.c b/gcc/testsuite/gcc.dg/torture/bitint-45.c
new file mode 100644 (file)
index 0000000..50c622d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/bitint-45.c
@@ -0,0 +1,32 @@
+/* PR middle-end/112750 */
+/* { dg-do run { target bitint } } */
+/* { dg-options "-std=c23 -pedantic-errors" } */
+/* { dg-skip-if "" { ! run_expensive_tests }  { "*" } { "-O0" "-O2" } } */
+/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
+
+#if __BITINT_MAXWIDTH__ >= 256
+_BitInt(256) a = __INT_MAX__ + (_BitInt(256)) 1;
+_BitInt(256) b = __INT_MAX__;
+#endif
+#if __BITINT_MAXWIDTH__ >= 512
+_BitInt(512) c = 0x7fffffffffffffffffffffffffffffffffffffffwb + (_BitInt(512)) 1;
+_BitInt(512) d = 0x7fffffffffffffffffffffffffffffffffffffffwb;
+#endif
+
+int
+main ()
+{
+#if __BITINT_MAXWIDTH__ >= 256
+  if (!__builtin_sub_overflow_p (a, 0, 0))
+    __builtin_abort ();
+  if (!__builtin_sub_overflow_p (b, -1, 0))
+    __builtin_abort ();
+#endif
+#if __BITINT_MAXWIDTH__ >= 512
+  if (!__builtin_sub_overflow_p (c, 0, (_BitInt(160)) 0))
+    __builtin_abort ();
+  if (!__builtin_sub_overflow_p (d, -1, 0))
+    __builtin_abort ();
+#endif
+  return 0;
+}