[gcc r15-1622] Add param for bb limit to invoke fast_vrp.

[Andrew Macleod]

https://gcc.gnu.org/g:1ea95cc5e099d554764b82df8e972129e9d20885

commit r15-1622-g1ea95cc5e099d554764b82df8e972129e9d20885
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Mon Jun 17 11:38:46 2024 -0400

    Add param for bb limit to invoke fast_vrp.
    
    If the basic block count is too high, simply use fast_vrp for all
    VRP passes.
    
            * doc/invoke.texi (vrp-block-limit): Document.
            * params.opt (param=vrp-block-limit): New.
            * tree-vrp.cc (fvrp_folder::execute): Invoke fast_vrp if block
            count exceeds limit.

Diff:
---
 gcc/doc/invoke.texi |  3 +++
 gcc/params.opt      |  4 ++++
 gcc/tree-vrp.cc     | 14 ++++++++++++--
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 23d90db2925..729dbc1691e 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -16849,6 +16849,9 @@ this parameter.  The default value of this parameter is 50.
 @item vect-induction-float
 Enable loop vectorization of floating point inductions.
 
+@item vrp-block-limit
+Maximum number of basic blocks before VRP switches to a lower memory algorithm.
+
 @item vrp-sparse-threshold
 Maximum number of basic blocks before VRP uses a sparse bitmap cache.
 
diff --git a/gcc/params.opt b/gcc/params.opt
index d34ef545bf0..c17ba17b91b 100644
--- a/gcc/params.opt
+++ b/gcc/params.opt
@@ -1198,6 +1198,10 @@ The maximum factor which the loop vectorizer applies to the cost of statements i
 Common Joined UInteger Var(param_vect_induction_float) Init(1) IntegerRange(0, 1) Param Optimization
 Enable loop vectorization of floating point inductions.
 
+-param=vrp-block-limit=
+Common Joined UInteger Var(param_vrp_block_limit) Init(150000) Optimization Param
+Maximum number of basic blocks before VRP switches to a fast model with less memory requirements.
+
 -param=vrp-sparse-threshold=
 Common Joined UInteger Var(param_vrp_sparse_threshold) Init(3000) Optimization Param
 Maximum number of basic blocks before VRP uses a sparse bitmap cache.
diff --git a/gcc/tree-vrp.cc b/gcc/tree-vrp.cc
index 26979b706e5..e184e9af51e 100644
--- a/gcc/tree-vrp.cc
+++ b/gcc/tree-vrp.cc
@@ -60,6 +60,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "ipa-cp.h"
 #include "ipa-prop.h"
 #include "attribs.h"
+#include "diagnostic-core.h"
 
 // This class is utilized by VRP and ranger to remove __builtin_unreachable
 // calls, and reflect any resulting global ranges.
@@ -1331,9 +1332,18 @@ public:
   unsigned int execute (function *fun) final override
     {
       // Check for fast vrp.
-      if (&data == &pass_data_fast_vrp)
+      bool use_fvrp = (&data == &pass_data_fast_vrp);
+      if (!use_fvrp && last_basic_block_for_fn (fun) > param_vrp_block_limit)
+	{
+	  use_fvrp = true;
+	  warning (OPT_Wdisabled_optimization,
+		   "Using fast VRP algorithm. %d basic blocks"
+		   " exceeds %<--param=vrp-block-limit=%d%> limit",
+		   n_basic_blocks_for_fn (fun),
+		   param_vrp_block_limit);
+	}
+      if (use_fvrp)
 	return execute_fast_vrp (fun, final_p);
-
       return execute_ranger_vrp (fun, final_p);
     }