diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index 0228282..437de38 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -738,6 +738,7 @@
   bool MadeChange = false;
 
   std::vector<TargetLowering::AsmOperandInfo> TargetConstraints = TLI->ParseConstraints(CS);
+  unsigned ArgNo = 0;
   for (unsigned i = 0, e = TargetConstraints.size(); i != e; ++i) {
     TargetLowering::AsmOperandInfo &OpInfo = TargetConstraints[i];
     
@@ -746,9 +747,10 @@
 
     if (OpInfo.ConstraintType == TargetLowering::C_Memory &&
         OpInfo.isIndirect) {
-      Value *OpVal = OpInfo.CallOperandVal;
+      Value *OpVal = const_cast<Value *>(CS.getArgument(ArgNo++));
       MadeChange |= OptimizeMemoryInst(I, OpVal, OpVal->getType(), SunkAddrs);
-    }
+    } else if (OpInfo.Type == InlineAsm::isInput)
+      ArgNo++;
   }
 
   return MadeChange;
diff --git a/test/CodeGen/X86/2010-09-16-asmcrash.ll b/test/CodeGen/X86/2010-09-16-asmcrash.ll
new file mode 100644
index 0000000..9bbd691
--- /dev/null
+++ b/test/CodeGen/X86/2010-09-16-asmcrash.ll
@@ -0,0 +1,56 @@
+; RUN: llc < %s -mtriple=x86_64-unknown-freebsd8.1 -o /dev/null
+; This formerly crashed, PR 8154.
+
+module asm ".weak sem_close"
+module asm ".equ sem_close, _sem_close"
+module asm ".weak sem_destroy"
+module asm ".equ sem_destroy, _sem_destroy"
+module asm ".weak sem_getvalue"
+module asm ".equ sem_getvalue, _sem_getvalue"
+module asm ".weak sem_init"
+module asm ".equ sem_init, _sem_init"
+module asm ".weak sem_open"
+module asm ".equ sem_open, _sem_open"
+module asm ".weak sem_post"
+module asm ".equ sem_post, _sem_post"
+module asm ".weak sem_timedwait"
+module asm ".equ sem_timedwait, _sem_timedwait"
+module asm ".weak sem_trywait"
+module asm ".equ sem_trywait, _sem_trywait"
+module asm ".weak sem_unlink"
+module asm ".equ sem_unlink, _sem_unlink"
+module asm ".weak sem_wait"
+module asm ".equ sem_wait, _sem_wait"
+
+%struct._sem = type { i32, %struct._usem }
+%struct._usem = type { i32, i32, i32 }
+
+define void @_sem_timedwait(%struct._sem* noalias %sem) nounwind ssp {
+entry:
+  br i1 undef, label %while.cond.preheader, label %sem_check_validity.exit
+
+while.cond.preheader:                             ; preds = %entry
+  %tmp4 = getelementptr inbounds %struct._sem* %sem, i64 0, i32 1, i32 1
+  br label %while.cond
+
+sem_check_validity.exit:                          ; preds = %entry
+  ret void
+
+while.cond:                                       ; preds = %while.body, %while.cond.preheader
+  br i1 undef, label %while.body, label %while.end
+
+while.body:                                       ; preds = %while.cond
+  %0 = call i8 asm sideeffect "\09lock ; \09\09\09cmpxchgl $2,$1 ;\09       sete\09$0 ;\09\091:\09\09\09\09# atomic_cmpset_int", "={ax},=*m,r,{ax},*m,~{memory},~{dirflag},~{fpsr},~{flags}"(i32* %tmp4, i32 undef, i32 undef, i32* %tmp4) nounwind, !srcloc !0
+  br i1 undef, label %while.cond, label %return
+
+while.end:                                        ; preds = %while.cond
+  br i1 undef, label %if.end18, label %return
+
+if.end18:                                         ; preds = %while.end
+  unreachable
+
+return:                                           ; preds = %while.end, %while.body
+  ret void
+}
+
+!0 = metadata !{i32 158484}