[Bug c++/109724] [10 regression] Huge memory usage when building qtwebengine's SkOpAngle.cpp since r10-11201-g051f78a5c1d699

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109724

--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
Reduced testcase.  I've reduced with

diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 666d7061aa8..31879fb761b 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -1558,6 +1558,7 @@ valueize_refs_1 (vec<vn_reference_op_s> *orig, bool
*value
ized_anything,
 {
   vn_reference_op_t vro;
   unsigned int i;
+  auto_bitmap visited;

   *valueized_anything = false;

@@ -1609,8 +1610,12 @@ valueize_refs_1 (vec<vn_reference_op_s> *orig, bool
*valueized_anything,
               && vro->opcode == SSA_NAME
               && (*orig)[i - 1].opcode == MEM_REF)
        {
+         tree name = vro->op0;
          if (vn_reference_maybe_forwprop_address (orig, &i))
-           *valueized_anything = true;
+           {
+             *valueized_anything = true;
+             gcc_assert (bitmap_set_bit (visited, SSA_NAME_VERSION (name)));
+           }
        }
       /* If it transforms a non-constant ARRAY_REF into a constant
         one, adjust the constant offset.  */

--

double &SkTMax(double &a, double &b) { return a ?: b; }
struct SkDPoint {
  double fX;
};
struct SkDCubic {
  SkDPoint &operator[](int n) { return fPts[n]; }
  SkDPoint fPts[4];
};
struct SkDCurve {
  SkDCubic fCubic;
  SkDPoint &operator[](int n) { return fCubic[n]; }
};
struct SkDCurveSweep {
  SkDCurve fCurve;
};
int endsIntersect_rPts;
double endsIntersect_maxX;
struct SkOpAngle {
  void endsIntersect();
  SkDCurveSweep fPart;
} endsIntersect_rh;
void SkOpAngle::endsIntersect() {
  for (int index = 0;; ++index) {
    SkDCurve &curve = index ? endsIntersect_rh.fPart.fCurve : fPart.fCurve;
    for (int idx2 = 0; endsIntersect_rPts; ++idx2) {
      SkDPoint &__trans_tmp_1 = curve[idx2];
      endsIntersect_maxX = SkTMax(endsIntersect_maxX, __trans_tmp_1.fX);
    }
  }
}