We cannot create an OpPhi for pointers, so we have to regenerate these
instructions instead.

Fixes KhronosGroup#3030
Fixes KhronosGroup#3266

KhronosGroup/glslang@9eef54b...3ee5f2f

$ git log 9eef54b..3ee5f2f --date=short --no-merges --format='%ad %ae %s'
2020-07-22 greg Update spirv-tools known-good to most recent stable
2020-07-19 vkushwaha Add changes for SPV_EXT_shader_atomic_float_add
2020-07-14 bclayton Limit visibility of symbols for internal libraries
2020-07-20 john SPV: Update to the latest SPIR-V headers.
2020-07-14 bclayton Deprecate InitializeDll functions
2020-07-14 bclayton Simplify PoolAlloc with use of thread_local.
2020-07-14 malcolm also search global variables assignment for live variables
2020-07-20 bclayton Drop support for VS2013
2020-07-20 bclayton Start glslang 11.0.0
2020-07-20 bclayton Finalize glslang 10.15.3847
2020-07-20 bclayton build_info: Fix parsing of versions with no flavor

Created with:
  roll-dep third_party/glslang

Roll third_party/spirv-headers/ 7f2ae11..979924c (1 commit)

KhronosGroup/SPIRV-Headers@7f2ae11...979924c

$ git log 7f2ae11..979924c --date=short --no-merges --format='%ad %ae %s'
2020-07-21 alanbaker Support SPV_KHR_terminate_invocation (KhronosGroup#163)

Created with:
  roll-dep third_party/spirv-headers

Roll third_party/spirv-tools/ c10d6ce..969f028 (18 commits)

KhronosGroup/SPIRV-Tools@c10d6ce...969f028

$ git log c10d6ce..969f028 --date=short --no-merges --format='%ad %ae %s'
2020-07-23 rharrison Change DEPS rolling script to point at external/ (KhronosGroup#3584)
2020-07-23 vasniktel spirv-fuzz: Create a helper in fuzzerutil to reuse function type (KhronosGroup#3572)
2020-07-23 vasniktel spirv-fuzz: Test usages of IdIsIrrelevant fact (KhronosGroup#3578)
2020-07-23 antonikarp spirv-fuzz: adds TransformationReplaceCopyMemoryWithLoadStore (KhronosGroup#3575)
2020-07-23 antonikarp spirv-fuzz: adds TransformationReplaceCopyObjectWithStoreLoad (KhronosGroup#3567)
2020-07-22 stevenperron Start SPIRV-Tools v2020.5
2020-07-22 stevenperron Finalize SPIRV-Tools v2020.4
2020-07-22 vasniktel spirv-fuzz: Fix usages of irrelevant constants (KhronosGroup#3566)
2020-07-22 stevenperron Update CHANGES
2020-07-22 alanbaker Support SPV_KHR_terminate_invocation (KhronosGroup#3568)
2020-07-22 stevenperron Sink pointer instructions in merge return (KhronosGroup#3569)
2020-07-21 greg Preserve OpenCL.DebugInfo.100 through elim-dead-code-aggressive (KhronosGroup#3542)
2020-07-21 vasniktel spirv-fuzz: TransformationReplaceParamsWithStruct (KhronosGroup#3455)
2020-07-21 38144211+vkushwaha-nv Add changes for SPV_EXT_shader_atomic_float (KhronosGroup#3562)
2020-07-21 vasniktel spirv-fuzz: Use irrelevant constants (KhronosGroup#3565)
2020-07-21 stefanomil spirv-fuzz: Extend TransformationRecordSynonymousConstants to allow composite constants (KhronosGroup#3537)
2020-07-21 vasniktel spirv-fuzz: Add is_irrelevant parameter (KhronosGroup#3563)
2020-07-20 vasniktel spirv-fuzz: Add IdIsIrrelevant fact (KhronosGroup#3561)

Created with:
  roll-dep third_party/spirv-tools