[gcc(refs/users/marxin/heads/PR96979-switch-clusters-speed)] Revert "switch lowering: limit number of cluster attemps"

[gcc(refs/users/marxin/heads/PR96979-switch-clusters-speed)] Revert "switch lowering: limit number of cluster attemps"

[Martin Liska]

https://gcc.gnu.org/g:e1956c0019d8df4a022ea17bc76f9e62fac182c7

commit e1956c0019d8df4a022ea17bc76f9e62fac182c7
Author: Martin Liska <mliska@suse.cz>
Date:   Thu Sep 24 13:34:58 2020 +0200

    Revert "switch lowering: limit number of cluster attemps"
    
    This reverts commit c6df6039e9180c580945266302ec14047d358364.

Diff:
---
 gcc/doc/invoke.texi                     |  4 ---
 gcc/params.opt                          |  4 ---
 gcc/testsuite/g++.dg/tree-ssa/pr96979.C | 50 ---------------------------------
 gcc/tree-switch-conversion.c            | 17 -----------
 4 files changed, 75 deletions(-)

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 75203ba2420..08f1102030c 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -13471,10 +13471,6 @@ The smallest number of different values for which it is best to use a
 jump-table instead of a tree of conditional branches.  If the value is
 0, use the default for the machine.
 
-@item max-switch-clustering-attempts
-The maximum number of clustering attempts used
-in bit-test and jump-table switch expansion.
-
 @item jump-table-max-growth-ratio-for-size
 The maximum code size growth ratio when expanding
 into a jump table (in percent).  The parameter is used when
diff --git a/gcc/params.opt b/gcc/params.opt
index 5f2e11d6c57..dcf5e020f01 100644
--- a/gcc/params.opt
+++ b/gcc/params.opt
@@ -82,10 +82,6 @@ The maximum length of a constant string for a builtin string cmp call eligible f
 Common Joined UInteger Var(param_case_values_threshold) Param Optimization
 The smallest number of different values for which it is best to use a jump-table instead of a tree of conditional branches, if 0, use the default for the machine.
 
--param=max-switch-clustering-attempts=
-Common Joined UInteger Var(param_max_switch_clustering_attempts) Param Optimization Init(10000)
-The maximum number of clustering attempts used in bit-test and jump-table switch expansion.
-
 -param=comdat-sharing-probability=
 Common Joined UInteger Var(param_comdat_sharing_probability) Init(20) Param Optimization
 Probability that COMDAT function will be shared with different compilation unit.
diff --git a/gcc/testsuite/g++.dg/tree-ssa/pr96979.C b/gcc/testsuite/g++.dg/tree-ssa/pr96979.C
deleted file mode 100644
index 85c703a140d..00000000000
--- a/gcc/testsuite/g++.dg/tree-ssa/pr96979.C
+++ /dev/null
@@ -1,50 +0,0 @@
-/* PR tree-optimization/96979 */
-/* { dg-do compile } */
-/* { dg-options "-std=c++17 -O2 -fdump-tree-switchlower1" } */
-
-using u64 = unsigned long long;
-
-constexpr inline u64
-foo (const char *str) noexcept
-{
-  u64 value = 0xcbf29ce484222325ULL;
-  for (u64 i = 0; str[i]; i++)
-    value = (value ^ u64(str[i])) * 0x100000001b3ULL;
-  return value;
-}
-
-struct V
-{
-  enum W
-  {
-#define A(n) n,
-#define B(n) A(n##0) A(n##1) A(n##2) A(n##3) A(n##4) A(n##5) A(n##6) A(n##7) A(n##8) A(n##9)
-#define C(n) B(n##0) B(n##1) B(n##2) B(n##3) B(n##4) B(n##5) B(n##6) B(n##7) B(n##8) B(n##9)
-#define D(n) C(n##0) C(n##1) C(n##2) C(n##3) C(n##4) C(n##5) C(n##6) C(n##7) C(n##8) C(n##9)
-#define E D(foo1) D(foo2) D(foo3)
-    E
-    last
-  };
-
-  constexpr static W
-  bar (const u64 h) noexcept
-  {
-    switch (h)
-      {
-#undef A
-#define F(n) #n
-#define A(n) case foo (F(n)): return n;
-        E
-      }
-    return last;
-  }
-};
-
-int
-baz (const char *s)
-{
-  const u64 h = foo (s);
-  return V::bar (h);
-}
-
-/* { dg-final { scan-tree-dump-times ";; Bail out: --param=max-switch-clustering-attempts reached" 2 "switchlower1" } } */
diff --git a/gcc/tree-switch-conversion.c b/gcc/tree-switch-conversion.c
index e6a2c7a6a84..186411ff3c4 100644
--- a/gcc/tree-switch-conversion.c
+++ b/gcc/tree-switch-conversion.c
@@ -1183,7 +1183,6 @@ jump_table_cluster::find_jump_tables (vec<cluster *> &clusters)
 
   min.quick_push (min_cluster_item (0, 0, 0));
 
-  HOST_WIDE_INT attempts = 0;
   for (unsigned i = 1; i <= l; i++)
     {
       /* Set minimal # of clusters with i-th item to infinite.  */
@@ -1195,14 +1194,6 @@ jump_table_cluster::find_jump_tables (vec<cluster *> &clusters)
 	  if (i - j < case_values_threshold ())
 	    s += i - j;
 
-	  if (attempts++ == param_max_switch_clustering_attempts)
-	    {
-	      if (dump_file)
-		fprintf (dump_file, ";; Bail out: "
-			 "--param=max-switch-clustering-attempts reached\n");
-	      return clusters.copy ();
-	    }
-
 	  /* Prefer clusters with smaller number of numbers covered.  */
 	  if ((min[j].m_count + 1 < min[i].m_count
 	       || (min[j].m_count + 1 == min[i].m_count
@@ -1317,7 +1308,6 @@ bit_test_cluster::find_bit_tests (vec<cluster *> &clusters)
 
   min.quick_push (min_cluster_item (0, 0, 0));
 
-  HOST_WIDE_INT attempts = 0;
   for (unsigned i = 1; i <= l; i++)
     {
       /* Set minimal # of clusters with i-th item to infinite.  */
@@ -1325,13 +1315,6 @@ bit_test_cluster::find_bit_tests (vec<cluster *> &clusters)
 
       for (unsigned j = 0; j < i; j++)
 	{
-	  if (attempts++ == param_max_switch_clustering_attempts)
-	    {
-	      if (dump_file)
-		fprintf (dump_file, ";; Bail out: "
-			 "--param=max-switch-clustering-attempts reached\n");
-	      return clusters.copy ();
-	    }
 	  if (min[j].m_count + 1 < min[i].m_count
 	      && can_be_handled (clusters, j, i - 1))
 	    min[i] = min_cluster_item (min[j].m_count + 1, j, INT_MAX);