Index: lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3456,8 +3456,13 @@
       SDValue IdxN = getValue(Idx);
 
       // If the index is smaller or larger than intptr_t, truncate or extend
-      // it.
-      IdxN = DAG.getSExtOrTrunc(IdxN, getCurSDLoc(), N.getValueType());
+      // it. Prefer a zext vs a sext if we can.
+      bool KnownZero, KnownOne;
+      ComputeSignBit(const_cast<Value*>(Idx), KnownZero, KnownOne, DL);
+      if (KnownZero)
+        IdxN = DAG.getZExtOrTrunc(IdxN, getCurSDLoc(), N.getValueType());
+      else
+        IdxN = DAG.getSExtOrTrunc(IdxN, getCurSDLoc(), N.getValueType());
 
       // If this is a multiply by a power of two, turn it into a shl
       // immediately.  This is a very common case.
Index: test/CodeGen/X86/gep-sext.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/gep-sext.ll
@@ -0,0 +1,49 @@
+; RUN: llc < %s 2>&1 | FileCheck %s
+
+target datalayout = "e-p:32:32"
+target triple = "x86_64-linux-unknown"
+
+
+declare void @use(i32)
+
+; Sign extension is manditory for the gep argument
+define void @test(i32* %p, i32 %index) {
+; CHECK-LABEL: test:
+; CHECK: movslq %esi, %rax
+; CHECK: movl (%rdi,%rax,4), %edi
+  %addr = getelementptr i32* %p, i32 %index
+  %val = load i32* %addr
+  call void @use(i32 %val)
+  ret void
+}
+
+; Zero extension is manditory since the high bits of %esi
+; aren't specified
+define void @test2(i32* %p, i32 %index) {
+; CHECK-LABEL: test2
+; CHECK: movl %esi, %eax
+; CHECK: movl (%rdi,%rax,4), %edi
+  %i = zext i32 %index to i64
+  %addr = getelementptr i32* %p, i64 %i
+  %val = load i32* %addr
+  call void @use(i32 %val)
+  ret void
+}
+define void @test3(i32* %p, i32 %index) {
+; CHECK-LABEL: test3
+; CHECK-NOT: movslq
+; CHECK: movl 352(%rdi), %eax
+; CHECK: movl 160(%rdi,%rax,4), %edi
+  %addr_begin = getelementptr i32* %p, i64 40
+  %addr_fixed = getelementptr i32* %addr_begin, i64 48
+  %val_fixed = load i32* %addr_fixed, !range !0
+  %addr = getelementptr i32* %addr_begin, i32 %val_fixed
+  %val = load i32* %addr
+  call void @use(i32 %val)
+  ret void
+}
+;;  !range !0
+!0 = !{i32 0, i32 2147483647}
+
+
+