Mesa has started to segfault to NULL pointer access during Sacha Willems' "raytracing" demo compute shader compilation.  I'm not seeing that with other cases, like happened with bug 104213.

Bisecting points this as the commit where these started:
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commit 6737b1b859aadad64e5fe04a92d196a672413e06
Author:     Jason Ekstrand <jason.ekstrand@intel.com>
AuthorDate: Tue Dec 5 22:51:53 2017 -0800
Commit:     Jason Ekstrand <jason.ekstrand@intel.com>
CommitDate: Mon Dec 11 22:28:34 2017 -0800

    spirv: Add basic type validation for OpLoad, OpStore, and OpCopyMemory
    
    Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
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The crash is due to OpStore validation:
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(gdb) break _vtn_fail
Function "_vtn_fail" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (_vtn_fail) pending.

(gdb) run
Starting program: raytracing 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Breakpoint 1, _vtn_fail (b=0x8a3b70, file=file@entry=0x7ffff6249f10 "../../../src/compiler/spirv/vtn_variables.c", line=line@entry=2009, 
    fmt=fmt@entry=0x7ffff624a7c8 "Value and pointer types of OpStore do not match") at ../../../src/compiler/spirv/spirv_to_nir.c:112

(gdb) c
Continuing.

Program received signal SIGSEGV, Segmentation fault.
anv_shader_compile_to_nir (pipeline=0x8a2e60, pipeline=0x8a2e60, spec_info=0x6bdd10, stage=MESA_SHADER_COMPUTE, entrypoint_name=0x7fffffffb3c0 "", 
    module=0x8a7dd0, mem_ctx=0x879c40) at ../../../src/intel/vulkan/anv_pipeline.c:153
153	   nir_shader *nir = entry_point->shader;
(gdb) bt
#0  anv_shader_compile_to_nir (pipeline=0x8a2e60, pipeline=0x8a2e60, spec_info=0x6bdd10, stage=MESA_SHADER_COMPUTE, entrypoint_name=0x7fffffffb3c0 "", 
    module=0x8a7dd0, mem_ctx=0x879c40) at ../../../src/intel/vulkan/anv_pipeline.c:153
#1  anv_pipeline_compile (pipeline=pipeline@entry=0x8a2e60, mem_ctx=mem_ctx@entry=0x879c40, module=module@entry=0x8a7dd0, 
    entrypoint=entrypoint@entry=0x45e14a "main", stage=stage@entry=MESA_SHADER_COMPUTE, spec_info=spec_info@entry=0x0, prog_data=0x7fffffffb3c0, 
    map=0x7fffffffb310) at ../../../src/intel/vulkan/anv_pipeline.c:395
#2  0x00007ffff5e323cc in anv_pipeline_compile_cs (pipeline=pipeline@entry=0x8a2e60, cache=cache@entry=0x8792a0, info=info@entry=0x7fffffffe4d0, 
    module=0x8a7dd0, entrypoint=0x45e14a "main", spec_info=0x0) at ../../../src/intel/vulkan/anv_pipeline.c:1019
#3  0x00007ffff5fbfe27 in compute_pipeline_create (_device=_device@entry=0x868c00, cache=cache@entry=0x8792a0, pCreateInfo=pCreateInfo@entry=0x7fffffffe4d0, 
    pAllocator=pAllocator@entry=0x0, pPipeline=pPipeline@entry=0x696890) at ../../../src/intel/vulkan/genX_pipeline.c:1770
#4  0x00007ffff5fd2916 in gen9_CreateComputePipelines (_device=0x868c00, pipelineCache=0x8792a0, count=1, pCreateInfos=<optimized out>, pAllocator=0x0, 
    pPipelines=0x696890) at ../../../src/intel/vulkan/genX_pipeline.c:1895
#5  0x00007ffff798ec65 in vkCreateComputePipelines () from VulkanTools/build/loader/libvulkan.so.1
#6  0x00000000004387c8 in VulkanExample::prepareCompute() ()
#7  0x00000000004393f9 in VulkanExample::prepare() ()
#8  0x0000000000432f92 in main ()

(gdb) info locals
device = <optimized out>
spec_entries = 0x0
spirv_options = {lower_workgroup_access_to_offsets = true, caps = {float64 = true, image_ms_array = false, tessellation = true, draw_parameters = true, 
    image_read_without_format = false, image_write_without_format = true, int64 = true, multiview = true, variable_pointers = true, storage_16bit = true}, 
  debug = {func = 0x0, private_data = 0x0}}
entry_point = <optimized out>
nir = <optimized out>
compiler = 0x6bdd10
nir_options = 0x7ffff6226000 <scalar_nir_options>
spirv = 0x8a7de8
num_spec_entries = 0

(gdb) disassemble 
Dump of assembler code for function anv_pipeline_compile:
...
   0x00007ffff5e30a50 <+256>:	callq  0x7ffff61d5170 <spirv_to_nir>
=> 0x00007ffff5e30a55 <+261>:	mov    0x18(%rax),%rbx
   0x00007ffff5e30a59 <+265>:	mov    0x20(%rsp),%rdi

(gdb) info registers rax rbx
rax            0x0	0
rbx            0x0	0
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Does this check need also relaxing?