[InstCombine] Add tests for freeze of recurrence with invoke start (NFC)

Author: nikic

llvm/test/Transforms/InstCombine/freeze.ll

@@ -740,8 +740,8 @@ exit:                                             ; preds = %loop
   ret void
 }
 
-define void @fold_phi_neg_flags(i32 %init, i32 %n) {
-; CHECK-LABEL: @fold_phi_neg_flags(
+define void @fold_phi_drop_flags(i32 %init, i32 %n) {
+; CHECK-LABEL: @fold_phi_drop_flags(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
@@ -917,6 +917,80 @@ exit:
   ret void
 }
 
+define void @fold_phi_invoke_start_value(i32 %n) personality i8* undef {
+; CHECK-LABEL: @fold_phi_invoke_start_value(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[INIT:%.*]] = invoke i32 @get_i32()
+; CHECK-NEXT:    to label [[LOOP:%.*]] unwind label [[UNWIND:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[INIT]], [[ENTRY:%.*]] ], [ [[I_NEXT:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[I_FR:%.*]] = freeze i32 [[I]]
+; CHECK-NEXT:    [[I_NEXT]] = add nuw nsw i32 [[I_FR]], 1
+; CHECK-NEXT:    [[COND:%.*]] = icmp eq i32 [[I_NEXT]], [[N:%.*]]
+; CHECK-NEXT:    br i1 [[COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       unwind:
+; CHECK-NEXT:    [[TMP0:%.*]] = landingpad i8
+; CHECK-NEXT:    cleanup
+; CHECK-NEXT:    unreachable
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %init = invoke i32 @get_i32()
+  to label %loop unwind label %unwind
+
+loop:
+  %i = phi i32 [ %init, %entry ], [ %i.next, %loop ]
+  %i.fr = freeze i32 %i
+  %i.next = add nsw nuw i32 %i.fr, 1
+  %cond = icmp eq i32 %i.next, %n
+  br i1 %cond, label %loop, label %exit
+
+unwind:
+  landingpad i8 cleanup
+  unreachable
+
+exit:
+  ret void
+}
+
+define void @fold_phi_invoke_noundef_start_value(i32 %n) personality i8* undef {
+; CHECK-LABEL: @fold_phi_invoke_noundef_start_value(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[INIT:%.*]] = invoke noundef i32 @get_i32()
+; CHECK-NEXT:    to label [[LOOP:%.*]] unwind label [[UNWIND:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[INIT]], [[ENTRY:%.*]] ], [ [[I_NEXT:%.*]], [[LOOP]] ]
+; CHECK-NEXT:    [[I_FR:%.*]] = freeze i32 [[I]]
+; CHECK-NEXT:    [[I_NEXT]] = add nuw nsw i32 [[I_FR]], 1
+; CHECK-NEXT:    [[COND:%.*]] = icmp eq i32 [[I_NEXT]], [[N:%.*]]
+; CHECK-NEXT:    br i1 [[COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       unwind:
+; CHECK-NEXT:    [[TMP0:%.*]] = landingpad i8
+; CHECK-NEXT:    cleanup
+; CHECK-NEXT:    unreachable
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %init = invoke noundef i32 @get_i32()
+  to label %loop unwind label %unwind
+
+loop:
+  %i = phi i32 [ %init, %entry ], [ %i.next, %loop ]
+  %i.fr = freeze i32 %i
+  %i.next = add nsw nuw i32 %i.fr, 1
+  %cond = icmp eq i32 %i.next, %n
+  br i1 %cond, label %loop, label %exit
+
+unwind:
+  landingpad i8 cleanup
+  unreachable
+
+exit:
+  ret void
+}
+
 define i8* @freeze_load_noundef(i8** %ptr) {
 ; CHECK-LABEL: @freeze_load_noundef(
 ; CHECK-NEXT:    [[P:%.*]] = load i8*, i8** [[PTR:%.*]], align 8, !noundef !0