[llvm] r310013 - [AMDGPU] Add missing hazard for DPP-after-EXEC-write

[Connor Abbott via llvm-commits]

Author: cwabbott
Date: Thu Aug  3 18:09:43 2017
New Revision: 310013

URL: http://llvm.org/viewvc/llvm-project?rev=310013&view=rev
Log:
[AMDGPU] Add missing hazard for DPP-after-EXEC-write

Summary:
Following the docs, we need at least 5 wait states between an EXEC write
and an instruction that uses DPP.

Reviewers: tstellar, arsenm

Subscribers: kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D34849

Modified:
    llvm/trunk/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
    llvm/trunk/test/CodeGen/AMDGPU/inserted-wait-states.mir

Modified: llvm/trunk/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AMDGPU/GCNHazardRecognizer.cpp?rev=310013&r1=310012&r2=310013&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AMDGPU/GCNHazardRecognizer.cpp (original)
+++ llvm/trunk/lib/Target/AMDGPU/GCNHazardRecognizer.cpp Thu Aug  3 18:09:43 2017
@@ -367,10 +367,13 @@ int GCNHazardRecognizer::checkVMEMHazard
 
 int GCNHazardRecognizer::checkDPPHazards(MachineInstr *DPP) {
   const SIRegisterInfo *TRI = ST.getRegisterInfo();
+  const SIInstrInfo *TII = ST.getInstrInfo();
 
-  // Check for DPP VGPR read after VALU VGPR write.
+  // Check for DPP VGPR read after VALU VGPR write and EXEC write.
   int DppVgprWaitStates = 2;
+  int DppExecWaitStates = 5;
   int WaitStatesNeeded = 0;
+  auto IsHazardDefFn = [TII] (MachineInstr *MI) { return TII->isVALU(*MI); };
 
   for (const MachineOperand &Use : DPP->uses()) {
     if (!Use.isReg() || !TRI->isVGPR(MF.getRegInfo(), Use.getReg()))
@@ -380,6 +383,10 @@ int GCNHazardRecognizer::checkDPPHazards
     WaitStatesNeeded = std::max(WaitStatesNeeded, WaitStatesNeededForUse);
   }
 
+  WaitStatesNeeded = std::max(
+      WaitStatesNeeded,
+      DppExecWaitStates - getWaitStatesSinceDef(AMDGPU::EXEC, IsHazardDefFn));
+
   return WaitStatesNeeded;
 }
 

Modified: llvm/trunk/test/CodeGen/AMDGPU/inserted-wait-states.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AMDGPU/inserted-wait-states.mir?rev=310013&r1=310012&r2=310013&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AMDGPU/inserted-wait-states.mir (original)
+++ llvm/trunk/test/CodeGen/AMDGPU/inserted-wait-states.mir Thu Aug  3 18:09:43 2017
@@ -13,6 +13,7 @@
   define amdgpu_kernel void @s_mov_fed_b32() { ret void }
   define amdgpu_kernel void @s_movrel() { ret void }
   define amdgpu_kernel void @v_interp() { ret void }
+  define amdgpu_kernel void @dpp() { ret void }
 
   define amdgpu_kernel void @mov_fed_hazard_crash_on_dbg_value(i32 addrspace(1)* %A) {
   entry:
@@ -477,6 +478,40 @@ body: |
     %vgpr0 = V_INTERP_MOV_F32 0, 0, 0, implicit %m0, implicit %exec
     S_ENDPGM
 ...
+
+...
+---
+
+# GCN-LABEL: name: dpp
+
+# VI-LABEL: bb.0:
+# VI: V_MOV_B32_e32
+# VI-NEXT: S_NOP 0
+# VI-NEXT: S_NOP 0
+# VI-NEXT: V_MOV_B32_dpp
+
+# VI-LABEL: bb.1:
+# VI: V_CMPX_EQ_I32_e32
+# VI-NEXT: S_NOP 0
+# VI-NEXT: S_NOP 0
+# VI-NEXT: S_NOP 0
+# VI-NEXT: S_NOP 0
+# VI-NEXT: S_NOP 0
+# VI-NEXT: V_MOV_B32_dpp
+
+name: dpp
+
+body: |
+  bb.0:
+    %vgpr0 = V_MOV_B32_e32 0, implicit %exec
+    %vgpr1 = V_MOV_B32_dpp %vgpr0, 0, 15, 15, 0, implicit %exec
+    S_BRANCH %bb.1
+
+  bb.1:
+    implicit %exec, implicit %vcc = V_CMPX_EQ_I32_e32 %vgpr0, %vgpr1, implicit %exec
+    %vgpr3 = V_MOV_B32_dpp %vgpr0, 0, 15, 15, 0, implicit %exec
+    S_ENDPGM
+...
 ---
 name:            mov_fed_hazard_crash_on_dbg_value
 alignment:       0