Index: llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
===================================================================
--- llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
+++ llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
@@ -18,6 +18,8 @@
 //
 //===---------------------------------------------------------------------===//
 
+#include "MCTargetDesc/PPCMCTargetDesc.h"
+#include "MCTargetDesc/PPCPredicates.h"
 #include "PPC.h"
 #include "PPCInstrBuilder.h"
 #include "PPCInstrInfo.h"
@@ -31,7 +33,6 @@
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/Support/Debug.h"
-#include "MCTargetDesc/PPCPredicates.h"
 
 using namespace llvm;
 
@@ -805,6 +806,107 @@
                       combineSEXTAndSHL(MI, ToErase);
         break;
       }
+      case PPC::RLWINM:
+      case PPC::RLWINMo:
+      case PPC::RLWINM8:
+      case PPC::RLWINM8o: {
+        unsigned FoldingReg = MI.getOperand(1).getReg();
+        if (!Register::isVirtualRegister(FoldingReg))
+          break;
+
+        MachineInstr *SrcMI = MRI->getVRegDef(FoldingReg);
+        if (SrcMI->getOpcode() != PPC::RLWINM &&
+            SrcMI->getOpcode() != PPC::RLWINMo &&
+            SrcMI->getOpcode() != PPC::RLWINM8 &&
+            SrcMI->getOpcode() != PPC::RLWINM8o)
+          break;
+        assert((MI.getOperand(2).isImm() && MI.getOperand(3).isImm() &&
+                MI.getOperand(4).isImm() && SrcMI->getOperand(2).isImm() &&
+                SrcMI->getOperand(3).isImm() && SrcMI->getOperand(4).isImm()) &&
+               "Invalid PPC::RLWINM Instruction!");
+        uint64_t SHSrc = SrcMI->getOperand(2).getImm();
+        uint64_t SHMI = MI.getOperand(2).getImm();
+        uint64_t MBSrc = SrcMI->getOperand(3).getImm();
+        uint64_t MBMI = MI.getOperand(3).getImm();
+        uint64_t MESrc = SrcMI->getOperand(4).getImm();
+        uint64_t MEMI = MI.getOperand(4).getImm();
+
+        assert((MEMI < 32 && MESrc < 32 && MBMI < 32 && MBSrc < 32) &&
+               "Invalid PPC::RLWINM Instruction!");
+
+        APInt MaskSrc = APInt::getBitsSet(32, 32 - MESrc - 1, 32 - MBSrc);
+        APInt MaskMI = APInt::getBitsSet(32, 32 - MEMI - 1, 32 - MBMI);
+
+        APInt RotatedSrcMask = MaskSrc.rotl(SHMI);
+        APInt FinalMask = RotatedSrcMask & MaskMI;
+
+        // If final mask is 0, MI result should be 0 too.
+        if (FinalMask.isNullValue()) {
+          bool Is64Bit = (MI.getOpcode() == PPC::RLWINM8 ||
+                          MI.getOpcode() == PPC::RLWINM8o);
+
+          LLVM_DEBUG(dbgs() << "Replace Instr: ");
+          LLVM_DEBUG(MI.dump());
+
+          if (MI.getOpcode() == PPC::RLWINM || MI.getOpcode() == PPC::RLWINM8) {
+            // Replace MI with "LI 0"
+            MI.RemoveOperand(4);
+            MI.RemoveOperand(3);
+            MI.RemoveOperand(2);
+            MI.getOperand(1).ChangeToImmediate(0);
+            MI.setDesc(TII->get(Is64Bit ? PPC::LI8 : PPC::LI));
+          } else {
+            // Replace MI with "ANDIo reg, 0"
+            MI.RemoveOperand(4);
+            MI.RemoveOperand(3);
+            MI.getOperand(2).setImm(0);
+            MI.setDesc(TII->get(Is64Bit ? PPC::ANDIo8 : PPC::ANDIo));
+          }
+          Simplified = true;
+          NumRotatesCollapsed++;
+
+          LLVM_DEBUG(dbgs() << "With: ");
+          LLVM_DEBUG(MI.dump());
+          break;
+        }
+
+        uint32_t NewMB, NewME;
+        if (isRunOfOnes((unsigned)(FinalMask.getZExtValue()), NewMB, NewME)) {
+          // About to replace MI.getOperand(1), clear its kill flag.
+          MI.getOperand(1).setIsKill(false);
+
+          // If FoldingReg has only one use and it it not RLWINMo and RLWINM8o,
+          // safe to delete its def SrcMI. Otherwise keep it.
+          if (MRI->hasOneNonDBGUse(FoldingReg) &&
+              (SrcMI->getOpcode() == PPC::RLWINM ||
+               SrcMI->getOpcode() == PPC::RLWINM8)) {
+            ToErase = SrcMI;
+            LLVM_DEBUG(dbgs() << "Delete dead instruction: ");
+            LLVM_DEBUG(SrcMI->dump());
+          }
+
+          LLVM_DEBUG(dbgs() << "Converting Instr: ");
+          LLVM_DEBUG(MI.dump());
+
+          uint16_t NewSH = (SHSrc + SHMI) % 32;
+          MI.getOperand(2).setImm(NewSH);
+          MI.getOperand(3).setImm(NewMB);
+          MI.getOperand(4).setImm(NewME);
+          MI.getOperand(1).setReg(SrcMI->getOperand(1).getReg());
+          if (SrcMI->getOperand(1).isKill()) {
+            MI.getOperand(1).setIsKill(true);
+            SrcMI->getOperand(1).setIsKill(false);
+          }
+
+          Simplified = true;
+          NumRotatesCollapsed++;
+
+          LLVM_DEBUG(dbgs() << "To: ");
+          LLVM_DEBUG(MI.dump());
+          break;
+        }
+        break;
+      }
       }
     }
 
Index: llvm/test/CodeGen/PowerPC/fold-rlwinm.mir
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/PowerPC/fold-rlwinm.mir
@@ -0,0 +1,110 @@
+# RUN: llc -ppc-asm-full-reg-names -mtriple=powerpc64le-unknown-linux-gnu \
+# RUN:   -run-pass ppc-mi-peepholes %s -o - -verify-machineinstrs | FileCheck %s
+
+---
+name: testFoldRLWINM
+#CHECK : name : testFoldRLWINM
+tracksRegLiveness: true
+body: |
+  bb.0.entry:
+    liveins: $x3
+    %0:g8rc = COPY $x3
+    %1:gprc = COPY %0.sub_32:g8rc
+    %2:gprc = RLWINM %1:gprc, 27, 5, 31
+    ; CHECK-NOT: %2:gprc = RLWINM %1:gprc, 27, 5, 31
+    %3:gprc = RLWINM %2:gprc, 19, 0, 12
+    ; CHECK: %3:gprc = RLWINM %1, 14, 0, 12
+    BLR8 implicit $lr8, implicit $rm
+...
+---
+name: testFoldRLWINMSrcWrapped
+#CHECK : name : testFoldRLWINMSrcWrapped
+tracksRegLiveness: true
+body: |
+  bb.0.entry:
+    liveins: $x3
+    %0:g8rc = COPY $x3
+    %1:gprc = COPY %0.sub_32:g8rc
+    %2:gprc = RLWINM %1:gprc, 27, 30, 10
+    ; CHECK-NOT: %2:gprc = RLWINM %1:gprc, 27, 30 ,10 
+    %3:gprc = RLWINM %2:gprc, 19, 0, 12
+    ; CHECK: %3:gprc = RLWINM %1, 14, 11, 12
+    BLR8 implicit $lr8, implicit $rm
+...
+---
+name: testFoldRLWINMUserWrapped
+#CHECK : name : testFoldRLWINMUserWrapped
+tracksRegLiveness: true
+body: |
+  bb.0.entry:
+    liveins: $x3
+    %0:g8rc = COPY $x3
+    %1:gprc = COPY %0.sub_32:g8rc
+    %2:gprc = RLWINM %1:gprc, 10, 5, 31
+    ; CHECK-NOT: %2:gprc = RLWINM %1:gprc, 10, 5, 31
+    %3:gprc = RLWINM %2:gprc, 10, 30, 5
+    ; CHECK: %3:gprc = RLWINM %1, 20, 30, 5
+    BLR8 implicit $lr8, implicit $rm
+...
+---
+name: testFoldRLWINMMultipleUses
+#CHECK : name : testFoldRLWINMMultipleUses
+tracksRegLiveness: true
+body: |
+  bb.0.entry:
+    liveins: $x3
+    %0:g8rc = COPY $x3
+    %1:gprc = COPY %0.sub_32:g8rc
+    %2:gprc = RLWINM killed %1:gprc, 27, 5, 31
+    ; CHECK: %2:gprc = RLWINM %1, 27, 5, 31
+    %3:gprc = RLWINM %2:gprc, 19, 0, 12
+    ; CHECK: %3:gprc = RLWINM killed %1, 14, 0, 12
+    STW %3:gprc, %2:gprc, 100 
+    ; CHECK: STW %3, %2, 100
+    BLR8 implicit $lr8, implicit $rm
+...
+---
+name: testFoldRLWINMToZero
+#CHECK : name : testFoldRLWINMToZero
+tracksRegLiveness: true
+body: |
+  bb.0.entry:
+    liveins: $x3
+    %0:g8rc = COPY $x3
+    %1:gprc = COPY %0.sub_32:g8rc
+    %2:gprc = RLWINM %1:gprc, 27, 5, 10
+    ; CHECK-NOT: %2:gprc = RLWINM %1:gprc, 27, 5, 10
+    %3:gprc = RLWINM %2:gprc, 8, 5, 10
+    ; CHECK: %3:gprc = LI 0
+    BLR8 implicit $lr8, implicit $rm
+...
+---
+name: testFoldRLWINMoToZero
+#CHECK : name : testFoldRLWINMoToZero
+tracksRegLiveness: true
+body: |
+  bb.0.entry:
+    liveins: $x3
+    %0:g8rc = COPY $x3
+    %1:gprc = COPY %0.sub_32:g8rc
+    %2:gprc = RLWINM %1:gprc, 27, 5, 10
+    ; CHECK-NOT: %2:gprc = RLWINM %1:gprc, 27, 5, 10
+    %3:gprc = RLWINMo %2:gprc, 8, 5, 10, implicit-def $cr0
+    ; CHECK: %3:gprc = ANDIo %2, 0, implicit-def $cr0
+    BLR8 implicit $lr8, implicit $rm
+...
+---
+name: testFoldRLWINMInvalidMask
+#CHECK : name : testFoldRLWINMInvalidMask
+tracksRegLiveness: true
+body: |
+  bb.0.entry:
+    liveins: $x3
+    %0:g8rc = COPY $x3
+    %1:gprc = COPY %0.sub_32:g8rc
+    %2:gprc = RLWINM %1:gprc, 20, 5, 31
+    ; CHECK: %2:gprc = RLWINM %1, 20, 5, 31
+    %3:gprc = RLWINM %2:gprc, 19, 10, 20
+    ; CHECK: %3:gprc = RLWINM %2, 19, 10, 20
+    BLR8 implicit $lr8, implicit $rm
+...