AMDGPU: Always set COMPUTE_PGM_RSRC2.ENABLE_TRAP_HANDLER to zero for AMDHSA as it is set by CP

[kzhuravl]

How does mesa handle it?

[t-tye]

LGTM

docs/AMDGPUUsage.rst

.. table:: compute_pgm_rsrc2 for GFX6-GFX9
      5:1     5 bits  USER_SGPR_COUNT                 The total number of SGPR
                                                      user data registers
                                                      requested. This number must
                                                      match the number of user
                                                      data registers enabled.
 
                                                      Used by CP to set up
                                                      ``COMPUTE_PGM_RSRC2.USER_SGPR``.
-     6       1 bit   ENABLE_TRAP_HANDLER             Set to 1 if code contains a
-                                                     TRAP instruction which
-                                                     requires a trap handler to
-                                                     be enabled.
-
-                                                     CP sets
-                                                     ``COMPUTE_PGM_RSRC2.TRAP_PRESENT``
-                                                     if the runtime has
-                                                     installed a trap handler
-                                                     regardless of the setting
-                                                     of this field.
+     6       1 bit   ENABLE_TRAP_HANDLER             Must be 0.
+
+                                                     This bit represents
+                                                     ``COMPUTE_PGM_RSRC2.TRAP_PRESENT``,
+                                                     which is set by the CP if
+                                                     the runtime has installed a
+                                                     trap handler.
      7       1 bit   ENABLE_SGPR_WORKGROUP_ID_X      Enable the setup of the
                                                      system SGPR register for
                                                      the work-group id in the X
                                                      dimension (see
                                                      :ref:`amdgpu-amdhsa-initial-kernel-execution-state`).
 
                                                      Used by CP to set up
                                                      ``COMPUTE_PGM_RSRC2.TGID_X_EN``.

lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp

void AMDGPUAsmPrinter::getSIProgramInfo(SIProgramInfo &ProgInfo,
   if (MFI->hasWorkItemIDZ())
     TIDIGCompCnt = 2;
   else if (MFI->hasWorkItemIDY())
     TIDIGCompCnt = 1;
 
   ProgInfo.ComputePGMRSrc2 =
       S_00B84C_SCRATCH_EN(ProgInfo.ScratchBlocks > 0) |
       S_00B84C_USER_SGPR(MFI->getNumUserSGPRs()) |
-      S_00B84C_TRAP_HANDLER(STM.isTrapHandlerEnabled()) |
+      // For AMDHSA, TRAP_HANDLER must be zero, as it is populated by the CP.
+      S_00B84C_TRAP_HANDLER(STM.isAmdHsaOS() ? 0 : STM.isTrapHandlerEnabled()) |
       S_00B84C_TGID_X_EN(MFI->hasWorkGroupIDX()) |
       S_00B84C_TGID_Y_EN(MFI->hasWorkGroupIDY()) |
       S_00B84C_TGID_Z_EN(MFI->hasWorkGroupIDZ()) |
       S_00B84C_TG_SIZE_EN(MFI->hasWorkGroupInfo()) |
       S_00B84C_TIDIG_COMP_CNT(TIDIGCompCnt) |
       S_00B84C_EXCP_EN_MSB(0) |
       // For AMDHSA, LDS_SIZE must be zero, as it is populated by the CP.
       S_00B84C_LDS_SIZE(STM.isAmdHsaOS() ? 0 : ProgInfo.LDSBlocks) |

test/CodeGen/AMDGPU/trap.ll

 ; MESA-TRAP:  .long   47180
 ; MESA-TRAP-NEXT: .long   208
 
 ; NOMESA-TRAP: .section .AMDGPU.config
 ; NOMESA-TRAP:  .long   47180
 ; NOMESA-TRAP-NEXT: .long   144
 
 ; GCN-LABEL: {{^}}hsa_trap:
-; HSA-TRAP: enable_trap_handler = 1
+; HSA-TRAP: enable_trap_handler = 0
 ; HSA-TRAP: s_mov_b64 s[0:1], s[4:5]
 ; HSA-TRAP: s_trap 2
 
 ; for llvm.trap in hsa path without ABI, direct generate s_endpgm instruction without any warning information
 ; NO-HSA-TRAP: enable_trap_handler = 0
 ; NO-HSA-TRAP: s_endpgm
 ; NO-HSA-TRAP: COMPUTE_PGM_RSRC2:TRAP_HANDLER: 0
 

 ; MESA-TRAP-NEXT: .long   208
 
 ; NOMESA-TRAP: .section .AMDGPU.config
 ; NOMESA-TRAP:  .long   47180
 ; NOMESA-TRAP-NEXT: .long   144
 
 ; GCN-WARNING: warning: <unknown>:0:0: in function hsa_debugtrap void (i32 addrspace(1)*): debugtrap handler not supported
 ; GCN-LABEL: {{^}}hsa_debugtrap:
-; HSA-TRAP: enable_trap_handler = 1
+; HSA-TRAP: enable_trap_handler = 0
 ; HSA-TRAP: s_trap 3
 ; HSA-TRAP: flat_store_dword v[0:1], v3
 
 ; for llvm.debugtrap in non-hsa path without ABI, generate a warning and a s_endpgm instruction
 ; NO-HSA-TRAP: enable_trap_handler = 0
 ; NO-HSA-TRAP: s_endpgm
 
 ; TRAP-BIT: enable_trap_handler = 1