[gcc/devel/rust/master] borrowck: Dump: handle infinite loops

[Thomas Schwinge via Gcc-cvs]

https://gcc.gnu.org/g:8aac66b06e352ed869b76098dd07273d813128fc

commit 8aac66b06e352ed869b76098dd07273d813128fc
Author: Jakub Dupak <d...@jakubdupak.com>
Date:   Thu Oct 19 11:04:29 2023 +0200

    borrowck: Dump: handle infinite loops
    
    gcc/rust/ChangeLog:
    
            * checks/errors/borrowck/rust-bir-dump.cc (simplify_cfg): Detech 
infinite loops.
    
    Signed-off-by: Jakub Dupak <d...@jakubdupak.com>

Diff:
---
 gcc/rust/checks/errors/borrowck/rust-bir-dump.cc | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/gcc/rust/checks/errors/borrowck/rust-bir-dump.cc 
b/gcc/rust/checks/errors/borrowck/rust-bir-dump.cc
index ba530983dade..66870ddeb565 100644
--- a/gcc/rust/checks/errors/borrowck/rust-bir-dump.cc
+++ b/gcc/rust/checks/errors/borrowck/rust-bir-dump.cc
@@ -1,5 +1,6 @@
 #include <numeric>
 #include "rust-bir-dump.h"
+#include "rust-diagnostics.h"
 
 namespace Rust {
 namespace BIR {
@@ -76,7 +77,21 @@ simplify_cfg (Function &func, std::vector<BasicBlockId> 
&bb_fold_map)
          const BasicBlock &bb = func.basic_blocks[bb_fold_map[i]];
          if (bb.statements.empty () && bb.is_goto_terminated ())
            {
-             bb_fold_map[i] = bb.successors.at (0);
+             auto dst = bb.successors.at (0);
+             if (bb_fold_map[dst] != dst)
+               {
+                 rust_error_at (
+                   UNKNOWN_LOCATION,
+                   "BIR DUMP: Cannot fold CFG, because it contains an "
+                   "infinite loop with no executable statements.");
+                 rust_inform (UNKNOWN_LOCATION,
+                              "Continuing with an unfolded CFG.");
+                 // Reverting the fold map to the original state.
+                 std::iota (bb_fold_map.begin (), bb_fold_map.end (), 0);
+                 stabilized = true;
+                 break;
+               }
+             bb_fold_map[i] = dst;
              stabilized = false;
            }
        }