Implement depth_first and inverse_depth_first range factory functions.

Also updated as many loops as I could find using df_begin/idf_begin -
strangely I found no uses of idf_begin. Is that just used out of tree?

Also a few places couldn't use df_begin because either they used the
member functions of the depth first iterators or had specific ordering
constraints (I added a comment in the latter case).

Based on a patch by Jim Grosbach. (Jim - you just had iterator_range<T>
where you needed iterator_range<idf_iterator<T>>)

llvm-svn: 206016

1 files changed, 4 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyInstructions.cpp b/llvm/lib/Transforms/Utils/SimplifyInstructions.cpp
index bbd65f17528..6762527cf76 100644
--- a/llvm/lib/Transforms/Utils/SimplifyInstructions.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyInstructions.cpp
@@ -55,9 +55,10 @@ namespace {
       bool Changed = false;
 
       do {
-        for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
-             DE = df_end(&F.getEntryBlock()); DI != DE; ++DI)
-          for (BasicBlock::iterator BI = DI->begin(), BE = DI->end(); BI != BE;) {
+        for (BasicBlock *BB : depth_first(&F.getEntryBlock()))
+          // Here be subtlety: the iterator must be incremented before the loop
+          // body (not sure why), so a range-for loop won't work here.
+          for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
             Instruction *I = BI++;
             // The first time through the loop ToSimplify is empty and we try to
             // simplify all instructions.  On later iterations ToSimplify is not