Index: lib/Target/WebAssembly/WebAssemblyRegisterInfo.cpp
===================================================================
--- lib/Target/WebAssembly/WebAssemblyRegisterInfo.cpp
+++ lib/Target/WebAssembly/WebAssemblyRegisterInfo.cpp
@@ -66,7 +66,7 @@
 
   assert(MFI.getObjectSize(FrameIndex) != 0 &&
          "We assume that variable-sized objects have already been lowered, "
-         "and don't have a frame index.");
+         "and don't use FrameIndex operands.");
   unsigned FrameRegister = getFrameRegister(MF);
 
   // If this is the address operand of a load or store, make it relative to SP
Index: test/CodeGen/WebAssembly/userstack.ll
===================================================================
--- test/CodeGen/WebAssembly/userstack.ll
+++ test/CodeGen/WebAssembly/userstack.ll
@@ -178,28 +178,31 @@
  ; CHECK-NEXT: i32.load $push[[L11:.+]]=, __stack_pointer($pop[[L10]])
  ; CHECK-NEXT: i32.const $push[[L12:.+]]=, 16
  ; CHECK-NEXT: i32.sub $push[[L23:.+]]=, $pop[[L11]], $pop[[L12]]
- ; CHECK: tee_local $push[[L22:.+]]=, $[[FP_temp:.+]]=, $pop[[L23]]
- ; CHECK: i32.store $drop=, __stack_pointer($pop{{.+}}), $pop[[L22]]
+ ; CHECK-NEXT: tee_local $push[[L22:.+]]=, $[[SP:.+]]=, $pop[[L23]]
+ ; CHECK-NEXT: i32.store $drop=, __stack_pointer($pop{{.+}}), $pop[[L22]]
 
  ; Alloc and write to a static alloca
- ; Currently the store doesn't use FP directly, because it's a local that
- ; hasn't received its final allocation yet.
- ; CHECK: copy_local $push[[L21:.+]]=, $[[FP_temp]]
- ; CHECK: tee_local $push[[pushedFP:.+]]=, $[[FP:.+]]=, $pop[[L21]]
- ; CHECK: i32.const $push[[L0:.+]]=, 101
- ; CHECK: i32.store $drop=, [[static_offset:.+]]($pop[[pushedFP]]), $pop[[L0]]
+ ; CHECK: copy_local $push[[L21:.+]]=, $[[SP]]
+ ; CHECK-NEXT: tee_local $push[[pushedFP:.+]]=, $[[FP:.+]]=, $pop[[L21]]
+ ; CHECK-NEXT: i32.const $push[[L0:.+]]=, 101
+ ; CHECK-NEXT: i32.store $drop=, [[static_offset:.+]]($pop[[pushedFP]]), $pop[[L0]]
  %static = alloca i32
  store volatile i32 101, i32* %static
 
  ; Decrement SP in the body by the dynamic amount.
  ; CHECK: i32.sub
  ; CHECK: tee_local $push{{.+}}=, $[[dynamic_local:.+]]=, $pop{{.+}}
+ ; CHECK: i32.store {{.*}} __stack_pointer
  %dynamic = alloca i32, i32 %alloc
 
+ ; Ensure we don't modify the frame pointer after assigning it.
+ ; CHECK-NOT: $[[FP]]=
+
+ ; Ensure the static address doesn't change after modifying the stack pointer.
  ; CHECK: i32.const $push[[L7:.+]]=, 102
- ; CHECK: i32.store $drop=, [[static_offset]]($[[FP]]), $pop[[L7]]
- ; CHECK: i32.const $push[[L8:.+]]=, 103
- ; CHECK: i32.store $drop=, 0($[[dynamic_local]]), $pop[[L8]]
+ ; CHECK-NEXT: i32.store $drop=, [[static_offset]]($[[FP]]), $pop[[L7]]
+ ; CHECK-NEXT: i32.const $push[[L8:.+]]=, 103
+ ; CHECK-NEXT: i32.store $drop=, 0($[[dynamic_local]]), $pop[[L8]]
  store volatile i32 102, i32* %static
  store volatile i32 103, i32* %dynamic
 
@@ -208,18 +211,24 @@
  ; CHECK: tee_local $push{{.+}}=, $[[dynamic2_local:.+]]=, $pop{{.+}}
  %dynamic.2 = alloca i32, i32 %alloc
 
+ ; CHECK-NOT: $[[FP]]=
+
+ ; Ensure neither the static nor dynamic address changes after the second
+ ; modification of the stack pointer.
  ; CHECK: i32.const $push[[L9:.+]]=, 104
- ; CHECK: i32.store $drop=, [[static_offset]]($[[FP]]), $pop[[L9]]
- ; CHECK: i32.const $push[[L10:.+]]=, 105
- ; CHECK: i32.store $drop=, 0($[[dynamic_local]]), $pop[[L10]]
- ; CHECK: i32.const $push[[L11:.+]]=, 106
- ; CHECK: i32.store $drop=, 0($[[dynamic2_local]]), $pop[[L11]]
+ ; CHECK-NEXT: i32.store $drop=, [[static_offset]]($[[FP]]), $pop[[L9]]
+ ; CHECK-NEXT: i32.const $push[[L10:.+]]=, 105
+ ; CHECK-NEXT: i32.store $drop=, 0($[[dynamic_local]]), $pop[[L10]]
+ ; CHECK-NEXT: i32.const $push[[L11:.+]]=, 106
+ ; CHECK-NEXT: i32.store $drop=, 0($[[dynamic2_local]]), $pop[[L11]]
  store volatile i32 104, i32* %static
  store volatile i32 105, i32* %dynamic
  store volatile i32 106, i32* %dynamic.2
 
  ; Writeback to memory.
- ; CHECK: i32.store $drop=, __stack_pointer($pop{{.+}}), $pop{{.+}}
+ ; CHECK: i32.const $push[[L17:.+]]=, 16
+ ; CHECK-NEXT: i32.add $push[[L18:.+]]=, $[[FP]], $pop[[L17]]
+ ; CHECK-NEXT: i32.store $drop=, __stack_pointer($pop{{.+}}), $pop[[L18]]
  ret void
 }