https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126533
Bug ID: 126533
Summary: Compile time hog with gori_name_helper
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Keywords: compile-time-hog
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: ktkachov at gcc dot gnu.org
Target Milestone: ---
/* gori_name_helper walks both SSA operands of every statement with no
memoisation, so a depth-N DAG of two-operand statements costs 2^N.
Entry point: gori_name_helper, gcc/gimple-range-gori.cc:1683, reached from
gori_name_on_edge (1729) <- dom_ranger::range_on_edge (gimple-range.cc:858)
<- fvrp_folder::value_on_edge, once per PHI argument.
The sibling walk gori_calc_operands (gimple-range-gori.cc:1617) memoises
with !r.has_range (si.ssaN) and is linear; this one has no cache, no depth
limit and no in_chain_p test.
Needs the fast-VRP path, selected automatically when the function has more
than --param=vrp-block-limit blocks (150000). Forced here with the param.
gcc -O2 --param=vrp-block-limit=1 does not finish in 40 s
gcc -O2 0.02 s
Depth 14 / 18 / 22 measure 0.35 s / 5.4 s / >40 s: one doubling per level.
Control: change "int r = u;" to "int r = a22;" so the queried name is the
condition operand and gori_name_helper returns at its first test; 0.02 s.
*/
extern int g1 (int);
int f (int i, int j, int k)
{
int u = k & 3;
int a0 = i & 255, b0 = j & 255;
int t1 = a0 * b0; int s1 = a0 - b0;
int a1 = t1 & 255; int b1 = s1 & 255;
int t2 = a1 * b1; int s2 = a1 - b1;
int a2 = t2 & 255; int b2 = s2 & 255;
int t3 = a2 * b2; int s3 = a2 - b2;
int a3 = t3 & 255; int b3 = s3 & 255;
int t4 = a3 * b3; int s4 = a3 - b3;
int a4 = t4 & 255; int b4 = s4 & 255;
int t5 = a4 * b4; int s5 = a4 - b4;
int a5 = t5 & 255; int b5 = s5 & 255;
int t6 = a5 * b5; int s6 = a5 - b5;
int a6 = t6 & 255; int b6 = s6 & 255;
int t7 = a6 * b6; int s7 = a6 - b6;
int a7 = t7 & 255; int b7 = s7 & 255;
int t8 = a7 * b7; int s8 = a7 - b7;
int a8 = t8 & 255; int b8 = s8 & 255;
int t9 = a8 * b8; int s9 = a8 - b8;
int a9 = t9 & 255; int b9 = s9 & 255;
int t10 = a9 * b9; int s10 = a9 - b9;
int a10 = t10 & 255; int b10 = s10 & 255;
int t11 = a10 * b10; int s11 = a10 - b10;
int a11 = t11 & 255; int b11 = s11 & 255;
int t12 = a11 * b11; int s12 = a11 - b11;
int a12 = t12 & 255; int b12 = s12 & 255;
int t13 = a12 * b12; int s13 = a12 - b12;
int a13 = t13 & 255; int b13 = s13 & 255;
int t14 = a13 * b13; int s14 = a13 - b13;
int a14 = t14 & 255; int b14 = s14 & 255;
int t15 = a14 * b14; int s15 = a14 - b14;
int a15 = t15 & 255; int b15 = s15 & 255;
int t16 = a15 * b15; int s16 = a15 - b15;
int a16 = t16 & 255; int b16 = s16 & 255;
int t17 = a16 * b16; int s17 = a16 - b16;
int a17 = t17 & 255; int b17 = s17 & 255;
int t18 = a17 * b17; int s18 = a17 - b17;
int a18 = t18 & 255; int b18 = s18 & 255;
int t19 = a18 * b18; int s19 = a18 - b18;
int a19 = t19 & 255; int b19 = s19 & 255;
int t20 = a19 * b19; int s20 = a19 - b19;
int a20 = t20 & 255; int b20 = s20 & 255;
int t21 = a20 * b20; int s21 = a20 - b20;
int a21 = t21 & 255; int b21 = s21 & 255;
int t22 = a21 * b21; int s22 = a21 - b21;
int a22 = t22 & 255; int b22 = s22 & 255;
int r = u;
if (a22 < 5) r = g1 (u);
return r;
}
