simplify-rtx: Fix up SUBREG_PROMOTED_SET arguments [PR104839]

The following testcase is miscompiled on powerpc64le-linux at -O1 and higher
(except for -Og).  The bug was introduced in r12-3252-gcad36f38576a6a7
which for SIGN_EXTEND from SUBREG_PROMOTED_SIGNED_P SUBREG used
SUBREG_PROMOTED_SET (temp, 1) (but that makes temp
SUBREG_PROMOTED_UNSIGNED_P because SRP_UNSIGNED is 1) and similarly the
ZERO_EXTEND from SUBREG_PROMOTED_UNSIGNED_P SUBREG used
SUBREG_PROMOTED_SET (temp, 0) (but that makes temp
SUBREG_PROMOTED_SIGNED_P because SRP_SIGNED is 0).
The following patch fixes that (swaps the 0s and 1s), but for better
readability uses the SRP_* constants.
rtl.h has:
/* Valid for subregs which are SUBREG_PROMOTED_VAR_P().  In that case
   this gives the necessary extensions:
   0  - signed (SPR_SIGNED)
   1  - normal unsigned (SPR_UNSIGNED)
   2  - value is both sign and unsign extended for mode
        (SPR_SIGNED_AND_UNSIGNED).
   -1 - pointer unsigned, which most often can be handled like unsigned
        extension, except for generating instructions where we need to
        emit special code (ptr_extend insns) on some architectures
        (SPR_POINTER). */
The expr.c change in the same commit looks ok to me (passes unsignedp
to SUBREG_PROMOTED_SET, so 0 for signed, 1 for unsigned).

2022-03-09  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/104839
	* simplify-rtx.cc (simplify_unary_operation_1) <case SIGN_EXTEND>:
	Use SRP_SIGNED instead of incorrect 1 in SUBREG_PROMOTED_SET.
	(simplify_unary_operation_1) <case ZERO_EXTEND>: Use SRP_UNSIGNED
	instead of incorrect 0 in SUBREG_PROMOTED_SET.

	* gcc.c-torture/execute/pr104839.c: New test.

diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index 3355b1a..5d4939c 100644 (file)
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -1527,7 +1527,7 @@ simplify_context::simplify_unary_operation_1 (rtx_code code, machine_mode mode,
                  if (partial_subreg_p (temp))
                    {
                      SUBREG_PROMOTED_VAR_P (temp) = 1;
-                     SUBREG_PROMOTED_SET (temp, 1);
+                     SUBREG_PROMOTED_SET (temp, SRP_SIGNED);
                    }
                  return temp;
                }
@@ -1662,7 +1662,7 @@ simplify_context::simplify_unary_operation_1 (rtx_code code, machine_mode mode,
                  if (partial_subreg_p (temp))
                    {
                      SUBREG_PROMOTED_VAR_P (temp) = 1;
-                     SUBREG_PROMOTED_SET (temp, 0);
+                     SUBREG_PROMOTED_SET (temp, SRP_UNSIGNED);
                    }
                  return temp;
                }

diff --git a/gcc/testsuite/gcc.c-torture/execute/pr104839.c b/gcc/testsuite/gcc.c-torture/execute/pr104839.c
new file mode 100644 (file)
index 0000000..1703df6
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr104839.c
@@ -0,0 +1,37 @@
+/* PR rtl-optimization/104839 */
+
+__attribute__((noipa)) short
+foo (void)
+{
+  return -1;
+}
+
+__attribute__((noipa)) int
+bar (void)
+{
+  short i = foo ();
+  if (i == -2)
+    return 2;
+  long k = i;
+  int j = -1;
+  volatile long s = 300;
+  if (k < 0)
+    {
+      k += s;
+      if (k < 0)
+       j = 0;
+    }
+  else if (k >= s)
+    j = 0;
+  if (j != -1)
+    return 1;
+  return 0;
+}
+
+int
+main ()
+{
+  if (bar () != 0)
+    __builtin_abort ();
+  return 0;
+}