[llvm-branch-commits] [llvm-branch] r282615 - Cherry pick r281957 (see http://llvm.org/PR30463)

[Matthias Braun via llvm-branch-commits]

Author: matze
Date: Wed Sep 28 13:17:12 2016
New Revision: 282615

URL: http://llvm.org/viewvc/llvm-project?rev=282615&view=rev
Log:
Cherry pick r281957 (see http://llvm.org/PR30463)


Added:
    llvm/branches/release_39/test/CodeGen/X86/branchfolding-undef.mir
      - copied unchanged from r281957, llvm/trunk/test/CodeGen/X86/branchfolding-undef.mir
Modified:
    llvm/branches/release_39/   (props changed)
    llvm/branches/release_39/lib/CodeGen/BranchFolding.cpp

Propchange: llvm/branches/release_39/
------------------------------------------------------------------------------
--- svn:mergeinfo (original)
+++ svn:mergeinfo Wed Sep 28 13:17:12 2016
@@ -1,3 +1,3 @@
 /llvm/branches/Apple/Pertwee:110850,110961
 /llvm/branches/type-system-rewrite:133420-134817
-/llvm/trunk:155241,275868-275870,275879,275898,275928,275935,275946,275978,275981,276015,276051,276077,276109,276119,276181,276209,276236-276237,276358,276364,276368,276389,276435,276438,276479,276510,276648,276676,276712,276740,276823,276956,276980,277093,277114,277135,277371,277399,277500,277504,277625,277691,277693,277773,278002,278086,278133,278157,278343,278370,278413,278558-278559,278562,278569,278571,278573,278575,278584,278841,278900,278938,278999,279125,279268,279369,279647
+/llvm/trunk:155241,275868-275870,275879,275898,275928,275935,275946,275978,275981,276015,276051,276077,276109,276119,276181,276209,276236-276237,276358,276364,276368,276389,276435,276438,276479,276510,276648,276676,276712,276740,276823,276956,276980,277093,277114,277135,277371,277399,277500,277504,277625,277691,277693,277773,278002,278086,278133,278157,278343,278370,278413,278558-278559,278562,278569,278571,278573,278575,278584,278841,278900,278938,278999,279125,279268,279369,279647,281957

Modified: llvm/branches/release_39/lib/CodeGen/BranchFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/branches/release_39/lib/CodeGen/BranchFolding.cpp?rev=282615&r1=282614&r2=282615&view=diff
==============================================================================
--- llvm/branches/release_39/lib/CodeGen/BranchFolding.cpp (original)
+++ llvm/branches/release_39/lib/CodeGen/BranchFolding.cpp Wed Sep 28 13:17:12 2016
@@ -776,9 +776,8 @@ bool BranchFolder::CreateCommonTailOnlyB
 }
 
 static void
-mergeMMOsFromMemoryOperations(MachineBasicBlock::iterator MBBIStartPos,
-                              MachineBasicBlock &MBBCommon) {
-  // Merge MMOs from memory operations in the common block.
+mergeOperations(MachineBasicBlock::iterator MBBIStartPos,
+                MachineBasicBlock &MBBCommon) {
   MachineBasicBlock *MBB = MBBIStartPos->getParent();
   // Note CommonTailLen does not necessarily matches the size of
   // the common BB nor all its instructions because of debug
@@ -808,8 +807,18 @@ mergeMMOsFromMemoryOperations(MachineBas
            "Reached BB end within common tail length!");
     assert(MBBICommon->isIdenticalTo(*MBBI) && "Expected matching MIIs!");
 
+    // Merge MMOs from memory operations in the common block.
     if (MBBICommon->mayLoad() || MBBICommon->mayStore())
       MBBICommon->setMemRefs(MBBICommon->mergeMemRefsWith(*MBBI));
+    // Drop undef flags if they aren't present in all merged instructions.
+    for (unsigned I = 0, E = MBBICommon->getNumOperands(); I != E; ++I) {
+      MachineOperand &MO = MBBICommon->getOperand(I);
+      if (MO.isReg() && MO.isUndef()) {
+        const MachineOperand &OtherMO = MBBI->getOperand(I);
+        if (!OtherMO.isUndef())
+          MO.setIsUndef(false);
+      }
+    }
 
     ++MBBI;
     ++MBBICommon;
@@ -928,8 +937,8 @@ bool BranchFolder::TryTailMergeBlocks(Ma
         continue;
       DEBUG(dbgs() << "BB#" << SameTails[i].getBlock()->getNumber()
                    << (i == e-1 ? "" : ", "));
-      // Merge MMOs from memory operations as needed.
-      mergeMMOsFromMemoryOperations(SameTails[i].getTailStartPos(), *MBB);
+      // Merge operations (MMOs, undef flags)
+      mergeOperations(SameTails[i].getTailStartPos(), *MBB);
       // Hack the end off BB i, making it jump to BB commonTailIndex instead.
       ReplaceTailWithBranchTo(SameTails[i].getTailStartPos(), MBB);
       // BB i is no longer a predecessor of SuccBB; remove it from the worklist.