Increase efficiency of sign_extend_inreg by using subregisters for truncation. As the README suggests sign_extend_subreg is selected to (sext(trunc)).

llvm-svn: 41010
diff --git a/llvm/test/CodeGen/X86/shl_elim.ll b/llvm/test/CodeGen/X86/shl_elim.ll
index 3c447f7..d3616f4 100644
--- a/llvm/test/CodeGen/X86/shl_elim.ll
+++ b/llvm/test/CodeGen/X86/shl_elim.ll
@@ -1,6 +1,6 @@
 ; RUN: llvm-as < %s | llc -march=x86 | grep {movl	8(.esp), %eax}
-; RUN: llvm-as < %s | llc -march=x86 | grep {shll	.15, .eax}
-; RUN: llvm-as < %s | llc -march=x86 | grep {sarl	.16, .eax}
+; RUN: llvm-as < %s | llc -march=x86 | grep {shrl	.eax}
+; RUN: llvm-as < %s | llc -march=x86 | grep {movswl	.ax, .eax}
 
 define i32 @test1(i64 %a) {
         %tmp29 = lshr i64 %a, 24                ; <i64> [#uses=1]