Index: lib/Target/PowerPC/PPCFastISel.cpp
===================================================================
--- lib/Target/PowerPC/PPCFastISel.cpp
+++ lib/Target/PowerPC/PPCFastISel.cpp
@@ -675,8 +675,18 @@
       case PPC::STFS: Opc = PPC::STFSX; break;
       case PPC::STFD: Opc = IsVSFRC ? PPC::STXSDX : PPC::STFDX; break;
     }
-    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Opc))
-      .addReg(SrcReg).addReg(Addr.Base.Reg).addReg(IndexReg);
+
+    auto MIB = BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Opc))
+        .addReg(SrcReg);
+
+    // If we have an index register defined we use it in the store inst,
+    // otherwise we use X0 as base as it makes the vector instructions to
+    // use zero in the computation of the effective address regardless the
+    // content of the register.
+    if (IndexReg)
+      MIB.addReg(Addr.Base.Reg).addReg(IndexReg);
+    else
+      MIB.addReg(PPC::ZERO8).addReg(Addr.Base.Reg);
   }
 
   return true;
Index: test/CodeGen/PowerPC/fast-isel-load-store-vsx.ll
===================================================================
--- /dev/null
+++ test/CodeGen/PowerPC/fast-isel-load-store-vsx.ll
@@ -0,0 +1,33 @@
+;; There are some known limitations in the VSX support during FastIsel 
+;; (see fast-isel-load-store.ll header). Nevertheless, we are adding some 
+;; regressions here for bugs we fix in the meantime
+; RUN: llc < %s -O0 -fast-isel -mattr=+vsx -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 | FileCheck %s --check-prefix=ELF64VSX
+
+;; The semantics of VSX stores for when R0 is used is different depending on
+;; whether it is used as base or offset. If used as base, the effective
+;; address computation will use zero regardless the content of R0. If used as
+;; offset, the content will be used in the effective address. We observed that
+;; for some constructors, the initialization values were being stored without
+;; any offset register being specified which was causing R0 to be used as offset
+;; in regions where it contained the value in the link register. This regression
+;; verifies that R0 is used as base in these situations.
+
+%SomeStruct = type { double }
+
+; ELF64VSX-LABEL: SomeStructCtor
+define linkonce_odr void @SomeStructCtor(%SomeStruct* %this, double %V) unnamed_addr align 2 {
+entry:
+  %this.addr = alloca %SomeStruct*, align 8
+  %V.addr = alloca double, align 8
+  store %SomeStruct* %this, %SomeStruct** %this.addr, align 8
+; ELF64VSX: stxsdx {{[0-9][0-9]?}}, 0, {{[1-9][0-9]?}}
+  store double %V, double* %V.addr, align 8
+  %this1 = load %SomeStruct*, %SomeStruct** %this.addr
+  %Val = getelementptr inbounds %SomeStruct, %SomeStruct* %this1, i32 0, i32 0
+; ELF64VSX: stxsdx {{[0-9][0-9]?}}, 0, {{[1-9][0-9]?}}
+  %0 = load double, double* %V.addr, align 8
+  store double %0, double* %Val, align 8
+  ret void
+ } 
+
+