Avoid exponential recursion when coercing nested conditional expressions.

This used to coerce the nesting tree twice at each condition, once for `coerce_to()` and once for `analyse_result_type()`, both calling each other for the entire subtree.

Closes https://github.com/cython/cython/issues/5197

2 files changed, 65 insertions, 9 deletions

diff --git a/Cython/Compiler/ExprNodes.py b/Cython/Compiler/ExprNodes.py
index 746e1772b..305eae9eb 100644
--- a/Cython/Compiler/ExprNodes.py
+++ b/Cython/Compiler/ExprNodes.py
@@ -12118,30 +12118,40 @@ class CondExprNode(ExprNode):
         return self.analyse_result_type(env)
 
     def analyse_result_type(self, env):
-        self.type = PyrexTypes.independent_spanning_type(
-            self.true_val.type, self.false_val.type)
+        true_val_type = self.true_val.type
+        false_val_type = self.false_val.type
+        self.type = PyrexTypes.independent_spanning_type(true_val_type, false_val_type)
+
         if self.type.is_reference:
             self.type = PyrexTypes.CFakeReferenceType(self.type.ref_base_type)
         if self.type.is_pyobject:
             self.result_ctype = py_object_type
         elif self.true_val.is_ephemeral() or self.false_val.is_ephemeral():
             error(self.pos, "Unsafe C derivative of temporary Python reference used in conditional expression")
-        if self.true_val.type.is_pyobject or self.false_val.type.is_pyobject:
-            self.true_val = self.true_val.coerce_to(self.type, env)
-            self.false_val = self.false_val.coerce_to(self.type, env)
+
+        if true_val_type.is_pyobject or false_val_type.is_pyobject:
+            if true_val_type != self.type:
+                self.true_val = self.true_val.coerce_to(self.type, env)
+            if false_val_type != self.type:
+                self.false_val = self.false_val.coerce_to(self.type, env)
+
         if self.type.is_error:
             self.type_error()
         return self
 
     def coerce_to_integer(self, env):
-        self.true_val = self.true_val.coerce_to_integer(env)
-        self.false_val = self.false_val.coerce_to_integer(env)
+        if not self.true_val.type.is_int:
+            self.true_val = self.true_val.coerce_to_integer(env)
+        if not self.false_val.type.is_int:
+            self.false_val = self.false_val.coerce_to_integer(env)
         self.result_ctype = None
         return self.analyse_result_type(env)
 
     def coerce_to(self, dst_type, env):
-        self.true_val = self.true_val.coerce_to(dst_type, env)
-        self.false_val = self.false_val.coerce_to(dst_type, env)
+        if self.true_val.type != dst_type:
+            self.true_val = self.true_val.coerce_to(dst_type, env)
+        if self.false_val.type != dst_type:
+            self.false_val = self.false_val.coerce_to(dst_type, env)
         self.result_ctype = None
         return self.analyse_result_type(env)
 
diff --git a/tests/run/if_else_expr.pyx b/tests/run/if_else_expr.pyx
index 41657ec5a..1d5143f22 100644
--- a/tests/run/if_else_expr.pyx
+++ b/tests/run/if_else_expr.pyx
@@ -1,5 +1,6 @@
 # mode: run
 # tag: condexpr
+# ticket: 5197
 
 cimport cython
 
@@ -67,3 +68,48 @@ def test_cfunc_ptrs(double x, bint round_down):
     3.0
     """
     return (math.floor if round_down else math.ceil)(x)
+
+
+def performance_gh5197(patternsList):
+    """
+    >>> performance_gh5197([])  # do not actually run anything, just see that things work at all
+    """
+    # Coercing the types in nested conditional expressions used to slow down exponentially.
+    # See https://github.com/cython/cython/issues/5197
+    import re
+    matched=[]
+    for _ in range(len(patternsList)):
+        try:
+            matched.append(patternsList[_].split('|')[-1].split('/')[-1] + 'pattr1' if re.search('^SomeString.*EndIng$')\
+                else patternsList[_].split('|a')[-1].split('/a')[-1] + 'pattr2' if re.search('^SomeOtherString.?Number.*EndIng$')\
+                    else patternsList[_].split('|a')[-1].split('/a')[-1] + 'pattr2' if re.search('^SomeOtherString.?Number.*EndIng$')\
+                        else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                            else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                    else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                        else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                            else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                    else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                        else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                            else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                    else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                        else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                            else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                    else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                        else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                            else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                                else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                                    else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                                        # else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                                        #     else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                                        #         else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                                        #             else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                                        #                 else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                                        #                     else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                                        #                         else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1] if re.search('^SomeOtherString.?Number.*EndIng$')\
+                                                                                                                                    else patternsList[_].split('|b')[-1].split('/b')[-1] + 'pattr2' + patternsList[_].split('/')[-1].split('//')[-1]  )
+        except Exception as e:
+            matched.append('Error at Indx:%s-%s' %(_, patternsList[_]))