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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/97467] [11 Regression] ICE in verify_range,
 at value-range.cc:369 (-Os and above) since r11-3685-gfcae5121154d1c33
Date: Mon, 19 Oct 2020 08:06:09 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97467

--- Comment #2 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
Ranger can figure out that the RHS operand of a shift is a zero and feeds i=
t to
operator_lshift::op1_range, which then uses it to create a swapped [1,0] ra=
nge.

Testing the following patch:

diff --git a/gcc/range-op.cc b/gcc/range-op.cc
index 0efa00186e8..30d2a4d3987 100644
--- a/gcc/range-op.cc
+++ b/gcc/range-op.cc
@@ -1579,6 +1579,11 @@ operator_lshift::op1_range (irange &r,
       wide_int shift =3D wi::to_wide (shift_amount);
       if (wi::lt_p (shift, 0, SIGNED))
        return false;
+      if (shift =3D=3D 0)
+       {
+         r =3D lhs;
+         return true;
+       }

       // Work completely in unsigned mode to start.
       tree utype =3D type;=