[gcc r14-3913] Checking undefined_p before using the vr

[gcc r14-3913] Checking undefined_p before using the vr

[Jiu Fu Guo]

https://gcc.gnu.org/g:8d8bc560b6ab7f3153db23ffb37157528e5b2c9a

commit r14-3913-g8d8bc560b6ab7f3153db23ffb37157528e5b2c9a
Author: Jiufu Guo <guojiufu@linux.ibm.com>
Date:   Wed Sep 6 21:38:11 2023 +0800

    Checking undefined_p before using the vr
    
    For pattern "(X + C) / N": "div (plus@3 @0 INTEGER_CST@1) INTEGER_CST@2)",
    Even if "X" has value-range and "X + C" does not overflow, "@3" may still
    be undefined. Like below example:
    
    _3 = _2 + -5;
    if (0 != 0)
      goto <bb 3>; [34.00%]
    else
      goto <bb 4>; [66.00%]
    ;;  succ:       3
    ;;              4
    
    ;; basic block 3, loop depth 0
    ;;  pred:       2
    _5 = _3 / 5;
    ;;  succ:       4
    
    The whole pattern "(_2 + -5 ) / 5" is in "bb 3", but "bb 3" would be
    unreachable (because "if (0 != 0)" is always false).
    And "get_range_query (cfun)->range_of_expr (vr3, @3)" is checked in
    "bb 3", "range_of_expr" gets an "undefined vr3". Where "@3" is "_5".
    
    So, before using "vr3", it would be safe to check "!vr3.undefined_p ()".
    
            PR tree-optimization/111303
    
    gcc/ChangeLog:
    
            * match.pd ((X - N * M) / N): Add undefined_p checking.
            ((X + N * M) / N): Likewise.
            ((X + C) div_rshift N): Likewise.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.dg/pr111303.c: New test.

Diff:
---
 gcc/match.pd                    |  3 +++
 gcc/testsuite/gcc.dg/pr111303.c | 11 +++++++++++
 2 files changed, 14 insertions(+)

diff --git a/gcc/match.pd b/gcc/match.pd
index 39c7ea1088f2..693638f8ca03 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -975,6 +975,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        /* "X+(N*M)" doesn't overflow.  */
        && range_op_handler (PLUS_EXPR).overflow_free_p (vr0, vr3)
        && get_range_query (cfun)->range_of_expr (vr4, @4)
+       && !vr4.undefined_p ()
        /* "X+N*M" is not with opposite sign as "X".  */
        && (TYPE_UNSIGNED (type)
 	   || (vr0.nonnegative_p () && vr4.nonnegative_p ())
@@ -995,6 +996,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        /* "X - (N*M)" doesn't overflow.  */
        && range_op_handler (MINUS_EXPR).overflow_free_p (vr0, vr3)
        && get_range_query (cfun)->range_of_expr (vr4, @4)
+       && !vr4.undefined_p ()
        /* "X-N*M" is not with opposite sign as "X".  */
        && (TYPE_UNSIGNED (type)
 	   || (vr0.nonnegative_p () && vr4.nonnegative_p ())
@@ -1025,6 +1027,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 	  /* "X+C" doesn't overflow.  */
 	  && range_op_handler (PLUS_EXPR).overflow_free_p (vr0, vr1)
 	  && get_range_query (cfun)->range_of_expr (vr3, @3)
+	  && !vr3.undefined_p ()
 	  /* "X+C" and "X" are not of opposite sign.  */
 	  && (TYPE_UNSIGNED (type)
 	      || (vr0.nonnegative_p () && vr3.nonnegative_p ())
diff --git a/gcc/testsuite/gcc.dg/pr111303.c b/gcc/testsuite/gcc.dg/pr111303.c
new file mode 100644
index 000000000000..eaabe55c105d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr111303.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+/* Make sure no ICE. */
+unsigned char a;
+int b(int c) {
+  if (c >= 5000)
+    return c / 5;
+}
+void d() { b(a - 5); }
+int main() {}