AMDGPU: AMDGPUUsage.rst minor corrections

[t-tye]

Summary

• Correct formating of table entry.
• Assembler support for GFX9.

[kzhuravl]

LGTM.

[t-tye]

• Correct targets that support XNACK.

llvm/trunk/docs/AMDGPUUsage.rst

then       Flat Scratch Init          2      This is 2 SGPRs:
                                                     FLAT_SCRATCH_LO which is
                                                     SGPRn-3 on GFX7 and SGPRn-5
                                                     on GFX8. FLAT_SCRATCH_LO is
                                                     used as the FLAT SCRATCH
                                                     SIZE in flat memory
                                                     instructions. Having CP load
                                                     it once avoids loading it at
                                                     the beginning of every
-                                                    wavefront. GFX9 This is the
+                                                    wavefront.
+                                                  GFX9
+                                                    This is the
                                                     64 bit base address of the
                                                     per SPI scratch backing
                                                     memory managed by SPI for
                                                     the queue executing the
                                                     kernel dispatch. CP obtains
                                                     this from the runtime (and
                                                     divides it if there are
                                                     multiple Shader Arrays each
                                                     with its own SPI). The value
                                                     of Scratch Wave Offset must
                                                     be added by the kernel
                                                     machine code and the result
                                                     moved to the FLAT_SCRATCH
                                                     SGPR which is SGPRn-6 and
                                                     SGPRn-5. It is used as the
                                                     FLAT SCRATCH BASE in flat
-                                                    memory instructions. then
-                                                    Private Segment Size 1 The
-                                                    32 bit byte size of a
-                                                    (enable_sgpr_private single
-                                                    work-item's
-                                                    scratch_segment_size) memory
-                                                    allocation. This is the
-                                                    value from the kernel
-                                                    dispatch packet Private
-                                                    Segment Byte Size rounded up
-                                                    by CP to a multiple of
-                                                    DWORD.
+                                                    memory instructions.
+     then       Private Segment Size       1      The 32 bit byte size of a
 
                                                   Having CP load it once avoids
                                                   loading it at the beginning of
                                                   every wavefront.
 
                                                   This is not used for
                                                   GFX7-GFX8 since it is the same
                                                   value as the second SGPR of
1. The low word of Flat Scratch Init is 32 bit byte offset from
      FLAT_SCRATCH_LO is in units of 256 bytes, the offset must be right shifted
      by 8 before moving into FLAT_SCRATCH_LO.
   2. The second word of Flat Scratch Init is 32 bit byte size of a single
      work-items scratch memory usage. This is directly loaded from the kernel
      dispatch packet Private Segment Byte Size and rounded up to a multiple of
      DWORD. Having CP load it once avoids loading it at the beginning of every
      wavefront. The prolog must move it to FLAT_SCRATCH_LO for use as FLAT SCRATCH
      SIZE.
+
 GFX9
   The Flat Scratch Init is the 64 bit address of the base of scratch backing
   memory being managed by SPI for the queue executing the kernel dispatch. The
   prolog must add the value of Scratch Wave Offset and moved to the FLAT_SCRATCH
   pair for use as the flat scratch base in flat memory instructions.
 
 .. _amdgpu-amdhsa-memory-model:
 

 
 .. TODO
    Specify what affect this has.
 
 Assembler
 ---------
 
 AMDGPU backend has LLVM-MC based assembler which is currently in development.
-It supports AMDGCN GFX6-GFX8.
+It supports AMDGCN GFX6-GFX9.
 
 This section describes general syntax for instructions and operands. For more
 information about instructions, their semantics and supported combinations of
 operands, refer to one of instruction set architecture manuals
 [AMD-GCN-GFX6]_, [AMD-GCN-GFX7]_, [AMD-GCN-GFX8]_ and [AMD-GCN-GFX9]_.
 
 An instruction has the following syntax (register operands are normally
 comma-separated while extra operands are space-separated):