Reinstate r146578; it doesn't appear to be the cause of some recent execution-

time regressions.  In general, it is beneficial to compile-time.

Original commit message:
Fix for bug #11429: Wrong behaviour for switches. Small improvement for code
size heuristics.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147175 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 84 insertions, 0 deletions

diff --git a/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll b/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll
new file mode 100644
index 0000000000..21c0ec3e22
--- /dev/null
+++ b/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll
@@ -0,0 +1,84 @@
+; RUN: opt -loop-unswitch -loop-unswitch-threshold 30 -disable-output -stats -info-output-file - < %s | FileCheck --check-prefix=STATS %s
+; RUN: opt -S -loop-unswitch -loop-unswitch-threshold 30 -verify-loop-info -verify-dom-info %s | FileCheck %s
+
+; STATS: 1 loop-simplify - Number of pre-header or exit blocks inserted
+; STATS: 1 loop-unswitch - Number of switches unswitched
+
+; ModuleID = '../llvm/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll'
+
+; CHECK:        %1 = icmp eq i32 %c, 1
+; CHECK-NEXT:   br i1 %1, label %.split.us, label %..split_crit_edge
+
+; CHECK:      ..split_crit_edge:                                ; preds = %0
+; CHECK-NEXT:   br label %.split
+
+; CHECK:      .split.us:                                        ; preds = %0
+; CHECK-NEXT:   br label %loop_begin.us
+
+; CHECK:      loop_begin.us:                                    ; preds = %loop_begin.backedge.us, %.split.us
+; CHECK:        switch i32 1, label %second_switch.us [
+; CHECK-NEXT:     i32 1, label %inc.us
+
+; CHECK:      inc.us:                                           ; preds = %second_switch.us, %loop_begin.us
+; CHECK-NEXT:   call void @incf() noreturn nounwind
+; CHECK-NEXT:   br label %loop_begin.backedge.us
+
+; CHECK:      second_switch.us:                                 ; preds = %loop_begin.us
+; CHECK-NEXT:   switch i32 %d, label %default.us [
+; CHECK-NEXT:     i32 1, label %inc.us
+; CHECK-NEXT:   ]
+
+; CHECK:      .split:                                           ; preds = %..split_crit_edge
+; CHECK-NEXT:   br label %loop_begin
+
+; CHECK:      loop_begin:                                       ; preds = %loop_begin.backedge, %.split
+; CHECK:        switch i32 %c, label %second_switch [
+; CHECK-NEXT:     i32 1, label %loop_begin.inc_crit_edge
+; CHECK-NEXT:   ]
+
+; CHECK:      loop_begin.inc_crit_edge:                         ; preds = %loop_begin
+; CHECK-NEXT:   br i1 true, label %us-unreachable, label %inc
+
+; CHECK:      second_switch:                                    ; preds = %loop_begin
+; CHECK-NEXT:   switch i32 %d, label %default [
+; CHECK-NEXT:     i32 1, label %inc
+; CHECK-NEXT:   ]
+
+; CHECK:      inc:                                              ; preds = %loop_begin.inc_crit_edge, %second_switch
+; CHECK-NEXT:   call void @incf() noreturn nounwind
+; CHECK-NEXT:   br label %loop_begin.backedge
+
+define i32 @test(i32* %var) {
+  %mem = alloca i32
+  store i32 2, i32* %mem
+  %c = load i32* %mem
+  %d = load i32* %mem
+
+  br label %loop_begin
+
+loop_begin:
+
+  %var_val = load i32* %var
+
+  switch i32 %c, label %second_switch [
+      i32 1, label %inc
+  ]
+
+second_switch:
+  switch i32 %d, label %default [
+      i32 1, label %inc
+  ]
+
+inc:
+  call void @incf() noreturn nounwind
+  br label %loop_begin
+
+default:  
+  br label %loop_begin
+
+loop_exit:
+  ret i32 0
+}
+
+declare void @incf() noreturn
+declare void @decf() noreturn