[PATCH] D22378: Make processInstruction from LCSSA.cpp externally available.

[Michael Zolotukhin via llvm-commits]

mzolotukhin created this revision.
mzolotukhin added reviewers: chandlerc, sanjoy, hfinkel.
mzolotukhin added a subscriber: llvm-commits.

When a pass tries to keep LCSSA form it's often convenient to be able to update
LCSSA for one instruction rather than for the entire loop. This patch makes the
processInstruction from LCSSA externally available under a name
formLCSSAForInstruction. The API is almost unchanged, and I'm open to
suggestions how to make it better. Currently for instance we have a couple of
arguments whose purpose might be not obvious for the routine user.

https://reviews.llvm.org/D22378

Files:
  include/llvm/Transforms/Utils/LoopUtils.h
  lib/Transforms/Utils/LCSSA.cpp

Index: lib/Transforms/Utils/LCSSA.cpp
===================================================================
--- lib/Transforms/Utils/LCSSA.cpp
+++ lib/Transforms/Utils/LCSSA.cpp
@@ -60,9 +60,10 @@
 /// Given an instruction in the loop, check to see if it has any uses that are
 /// outside the current loop.  If so, insert LCSSA PHI nodes and rewrite the
 /// uses.
-static bool processInstruction(Loop &L, Instruction &Inst, DominatorTree &DT,
-                               const SmallVectorImpl<BasicBlock *> &ExitBlocks,
-                               PredIteratorCache &PredCache, LoopInfo *LI) {
+bool llvm::formLCSSAForInstruction(
+    Loop &L, Instruction &Inst, DominatorTree &DT, LoopInfo &LI,
+    const SmallVectorImpl<BasicBlock *> &ExitBlocks,
+    PredIteratorCache &PredCache) {
   SmallVector<Use *, 16> UsesToRewrite;
 
   // Tokens cannot be used in PHI nodes, so we skip over them.
@@ -145,7 +146,7 @@
     // have uses outside of L2. Remember all PHIs in such situation as to
     // revisit than later on. FIXME: Remove this if indirectbr support into
     // LoopSimplify gets improved.
-    if (auto *OtherLoop = LI->getLoopFor(ExitBB))
+    if (auto *OtherLoop = LI.getLoopFor(ExitBB))
       if (!L.contains(OtherLoop))
         PostProcessPHIs.push_back(PN);
   }
@@ -181,16 +182,16 @@
       continue;
 
     BasicBlock *PHIBB = I->getParent();
-    Loop *OtherLoop = LI->getLoopFor(PHIBB);
+    Loop *OtherLoop = LI.getLoopFor(PHIBB);
     SmallVector<BasicBlock *, 8> EBs;
     OtherLoop->getExitBlocks(EBs);
     if (EBs.empty())
       continue;
 
     // Recurse and re-process each PHI instruction. FIXME: we should really
     // convert this entire thing to a worklist approach where we process a
     // vector of instructions...
-    processInstruction(*OtherLoop, *I, DT, EBs, PredCache, LI);
+    formLCSSAForInstruction(*OtherLoop, *I, DT, LI, EBs, PredCache);
   }
 
   // Remove PHI nodes that did not have any uses rewritten.
@@ -243,7 +244,7 @@
            !isa<PHINode>(I.user_back())))
         continue;
 
-      Changed |= processInstruction(L, I, DT, ExitBlocks, PredCache, LI);
+      Changed |= formLCSSAForInstruction(L, I, DT, *LI, ExitBlocks, PredCache);
     }
   }
 
Index: include/llvm/Transforms/Utils/LoopUtils.h
===================================================================
--- include/llvm/Transforms/Utils/LoopUtils.h
+++ include/llvm/Transforms/Utils/LoopUtils.h
@@ -323,6 +323,25 @@
 BasicBlock *InsertPreheaderForLoop(Loop *L, DominatorTree *DT, LoopInfo *LI,
                                    bool PreserveLCSSA);
 
+/// \brief Ensures LCSSA form for instruction Inst in the scope of loop L.
+///
+/// For the given instruction in the loop which have uses outside of the loop,
+/// an LCSSA PHI node is inserted and the uses outside the loop are rewritten to
+/// use this node.
+///
+/// LoopInfo and DominatorTree are required and preserved.
+/// ExitBlocks is a vector containing exit blocks of the loop L.
+/// PredCache should be a valid PredIteratorCache object.
+///
+/// ExitBlocks and PredCache are used to avoid redundant recomputations for
+/// every call of this routine.
+///
+/// Returns true if any modifications are made.
+bool formLCSSAForInstruction(Loop &L, Instruction &Inst, DominatorTree &DT,
+                             LoopInfo &LI,
+                             const SmallVectorImpl<BasicBlock *> &ExitBlocks,
+                             PredIteratorCache &PredCache);
+
 /// \brief Put loop into LCSSA form.
 ///
 /// Looks at all instructions in the loop which have uses outside of the


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D22378.64029.patch
Type: text/x-patch
Size: 3594 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20160714/e782ccea/attachment.bin>