AMDGPU: Add Vega12 and Vega20

Changes by
  Matt Arsenault
  Konstantin Zhuravlyov

llvm-svn: 331215
diff --git a/llvm/docs/AMDGPUUsage.rst b/llvm/docs/AMDGPUUsage.rst
index 886c378..7d358df 100644
--- a/llvm/docs/AMDGPUUsage.rst
+++ b/llvm/docs/AMDGPUUsage.rst
@@ -200,6 +200,16 @@
                                                                       - Radeon Instinct MI25
      ``gfx902``                  ``amdgcn``   APU   - xnack           - Ryzen 3 2200G
                                                       [on]            - Ryzen 5 2400G
+     ``gfx904``                  ``amdgcn``   dGPU  - xnack           *TBA*
+                                                      [off]
+                                                                      .. TODO
+                                                                         Add product
+                                                                         names.
+     ``gfx906``                  ``amdgcn``   dGPU  - xnack           *TBA*
+                                                      [off]
+                                                                      .. TODO
+                                                                         Add product
+                                                                         names.
      =========== =============== ============ ===== ========= ======= ==================
 
 .. _amdgpu-target-features:
@@ -547,8 +557,8 @@
      ``EF_AMDGPU_MACH_AMDGCN_GFX810``  0x02b      ``gfx810``
      ``EF_AMDGPU_MACH_AMDGCN_GFX900``  0x02c      ``gfx900``
      ``EF_AMDGPU_MACH_AMDGCN_GFX902``  0x02d      ``gfx902``
-     *reserved*                        0x02e      Reserved.
-     *reserved*                        0x02f      Reserved.
+     ``EF_AMDGPU_MACH_AMDGCN_GFX904``  0x02e      ``gfx904``
+     ``EF_AMDGPU_MACH_AMDGCN_GFX906``  0x02f      ``gfx906``
      *reserved*                        0x030      Reserved.
      ================================= ========== =============================
 
@@ -765,7 +775,7 @@
      ``R_AMDGPU_ABS32_HI``      Static, 2      ``word32``  (S + A) >> 32
                                 Dynamic
      ``R_AMDGPU_ABS64``         Static, 3      ``word64``  S + A
-                                Dynamic 
+                                Dynamic
      ``R_AMDGPU_REL32``         Static  4      ``word32``  S + A - P
      ``R_AMDGPU_REL64``         Static  5      ``word64``  S + A - P
      ``R_AMDGPU_ABS32``         Static, 6      ``word32``  S + A
@@ -784,7 +794,7 @@
 
 There is no current OS loader support for 32 bit programs and so
 ``R_AMDGPU_ABS32`` is not used.
-     
+
 .. _amdgpu-dwarf:
 
 DWARF