Unify alloca, outgoing arg, and prolog construction

tests_lit/llvm2ice_tests/nacl-other-intrinsics.ll

 ; This tests the NaCl intrinsics not related to atomic operations.
 
 ; RUN: %if --need=target_X8632 --command %p2i --filetype=obj --disassemble \
 ; RUN:   --target x8632 -i %s --args -O2 -sandbox \
 ; RUN:   -allow-externally-defined-symbols \
 ; RUN:   | %if --need=target_X8632 --command FileCheck %s
 ; RUN: %if --need=target_X8632 --command %p2i --filetype=obj --disassemble \
 ; RUN:   --target x8632 -i %s --args -Om1 -sandbox \
 ; RUN:   -allow-externally-defined-symbols \
 ; RUN:   | %if --need=target_X8632 --command FileCheck %s
@@ skipping 522 matching lines @@
   %__10 = bitcast i8* %tmp2 to i32*
   store i32 %x, i32* %__10, align 1
 
   %__11 = bitcast i8* %tmp3 to i32*
   store i32 %x, i32* %__11, align 1
 
   call void @llvm.stackrestore(i8* %sp1)
   ret void
 }
 ; CHECK-LABEL: test_stacksave_multiple
-; At least 3 copies of esp, but probably more from having to do the allocas.
+; lea is used to copy from esp for the allocas.
+; Otherwise, only one stacksave is live.
+; CHECK: mov ebp,esp
 ; CHECK: mov {{.*}},esp
-; CHECK: mov {{.*}},esp
-; CHECK: mov {{.*}},esp
+; CHECK: lea {{.*}},[esp+0x10]
+; CHECK: lea {{.*}},[esp+0x10]
+; CHECK: call
 ; CHECK: mov esp,{{.*}}
+; CHECK: mov esp,ebp
 ; ARM32-LABEL: test_stacksave_multiple
 ; ARM32: mov {{.*}}, sp
 ; ARM32: mov {{.*}}, sp
 ; ARM32: mov {{.*}}, sp
 ; ARM32: mov sp, {{.*}}