MISched: Don't schedule regions with 0 instructions

I think this is correct, but may not necessarily be the correct fix
for the assertion I'm really trying to solve. If a scheduling region
was found that only has dbg_value instructions, the RegPressure
tracker would end up in an inconsistent state because it would skip
over any debug instructions and point to an instruction outside of the
scheduling region. It may still be possible for this to happen if
there are some real schedulable instructions between dbg_values, but I
haven't managed to break this.

The testcase is extremely sensitive and I'm not sure how to make it
more resistent to future scheduler changes that would avoid stressing
this situation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356926 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/MachineScheduler.cpp b/lib/CodeGen/MachineScheduler.cpp
index 66d3a281d42dbb6c5c81f347a315b65e191295ac..88f0630f014f73d2fb3ce8d20050db00164c9527 100644 (file)
--- a/lib/CodeGen/MachineScheduler.cpp
+++ b/lib/CodeGen/MachineScheduler.cpp
@@ -486,13 +486,17 @@ getSchedRegions(MachineBasicBlock *MBB,
       MachineInstr &MI = *std::prev(I);
       if (isSchedBoundary(&MI, &*MBB, MF, TII))
         break;
-      if (!MI.isDebugInstr())
+      if (!MI.isDebugInstr()) {
         // MBB::size() uses instr_iterator to count. Here we need a bundle to
         // count as a single instruction.
         ++NumRegionInstrs;
+      }
     }
 
-    Regions.push_back(SchedRegion(I, RegionEnd, NumRegionInstrs));
+    // It's possible we found a scheduling region that only has debug
+    // instructions. Don't bother scheduling these.
+    if (NumRegionInstrs != 0)
+      Regions.push_back(SchedRegion(I, RegionEnd, NumRegionInstrs));
   }
 
   if (RegionsTopDown)

diff --git a/test/CodeGen/AMDGPU/sched-assert-onlydbg-value-empty-region.mir b/test/CodeGen/AMDGPU/sched-assert-onlydbg-value-empty-region.mir
new file mode 100644 (file)
index 0000000..d60abaf
--- /dev/null
+++ b/test/CodeGen/AMDGPU/sched-assert-onlydbg-value-empty-region.mir
@@ -0,0 +1,115 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx900 -run-pass=machine-scheduler -verify-machineinstrs %s -o - | FileCheck %s
+
+# The sequence of DBG_VALUEs forms a scheduling region with 0 real
+# instructions. The RegPressure tracker would end up skipping over any
+# debug instructions, so it would point to the instruction
+# before/outside of the region, hitting this assert:
+#  assert((BotRPTracker.getPos() == RegionEnd ||
+#          (RegionEnd->isDebugInstr() &&
+#           BotRPTracker.getPos() == priorNonDebug(RegionEnd, RegionBegin))) &&
+#         "Can't find the region bottom");
+
+---
+name:            only_dbg_value_sched_region
+tracksRegLiveness: true
+machineFunctionInfo:
+  isEntryFunction: true
+  waveLimiter:     true
+body:             |
+  ; CHECK-LABEL: name: only_dbg_value_sched_region
+  ; CHECK: bb.0:
+  ; CHECK:   successors: %bb.1(0x80000000)
+  ; CHECK:   liveins: $vgpr0
+  ; CHECK:   [[COPY:%[0-9]+]]:vgpr_32 = COPY $vgpr0
+  ; CHECK:   [[DEF:%[0-9]+]]:vreg_64 = IMPLICIT_DEF
+  ; CHECK:   [[GLOBAL_LOAD_DWORDX2_:%[0-9]+]]:vreg_64 = GLOBAL_LOAD_DWORDX2 [[DEF]], 0, 0, 0, implicit $exec
+  ; CHECK:   [[GLOBAL_LOAD_DWORD:%[0-9]+]]:vgpr_32 = GLOBAL_LOAD_DWORD [[DEF]], 8, 0, 0, implicit $exec
+  ; CHECK:   undef %4.sub1:vreg_64 = V_ADD_U32_e32 [[COPY]], [[COPY]], implicit $exec
+  ; CHECK:   %4.sub0:vreg_64 = V_MOV_B32_e32 111, implicit $exec
+  ; CHECK:   [[DEF1:%[0-9]+]]:vreg_64 = IMPLICIT_DEF
+  ; CHECK:   [[DEF2:%[0-9]+]]:vreg_64 = IMPLICIT_DEF
+  ; CHECK:   [[DEF3:%[0-9]+]]:vreg_64 = IMPLICIT_DEF
+  ; CHECK:   undef %11.sub1:vreg_64 = IMPLICIT_DEF
+  ; CHECK:   [[DEF4:%[0-9]+]]:vreg_64 = IMPLICIT_DEF
+  ; CHECK:   [[DEF5:%[0-9]+]]:vreg_64 = IMPLICIT_DEF
+  ; CHECK:   [[V_MOV_B32_e32_:%[0-9]+]]:vgpr_32 = V_MOV_B32_e32 0, implicit $exec
+  ; CHECK:   [[V_MOV_B32_e32_1:%[0-9]+]]:vgpr_32 = V_MOV_B32_e32 0, implicit $exec
+  ; CHECK:   [[DEF6:%[0-9]+]]:vgpr_32 = IMPLICIT_DEF
+  ; CHECK:   [[DEF7:%[0-9]+]]:vgpr_32 = IMPLICIT_DEF
+  ; CHECK:   [[COPY1:%[0-9]+]]:vreg_64 = COPY [[GLOBAL_LOAD_DWORDX2_]]
+  ; CHECK:   undef %6.sub0:vreg_64 = V_ADD_F32_e32 [[DEF]].sub0, [[COPY1]].sub0, implicit $exec
+  ; CHECK:   dead undef %6.sub1:vreg_64 = V_ADD_F32_e32 [[DEF]].sub1, [[COPY1]].sub0, implicit $exec
+  ; CHECK:   [[GLOBAL_LOAD_DWORD1:%[0-9]+]]:vgpr_32 = GLOBAL_LOAD_DWORD [[COPY1]], 0, 0, 0, implicit $exec
+  ; CHECK:   [[DEF8:%[0-9]+]]:vgpr_32 = IMPLICIT_DEF
+  ; CHECK:   undef %19.sub0:vreg_64 = V_ADD_F32_e32 [[GLOBAL_LOAD_DWORD1]], [[GLOBAL_LOAD_DWORDX2_]].sub0, implicit $exec
+  ; CHECK:   %19.sub1:vreg_64 = V_ADD_F32_e32 [[GLOBAL_LOAD_DWORD]], [[GLOBAL_LOAD_DWORD]], implicit $exec
+  ; CHECK:   GLOBAL_STORE_DWORDX2 %19, %4, 32, 0, 0, implicit $exec
+  ; CHECK:   %11.sub0:vreg_64 = GLOBAL_LOAD_DWORD [[DEF1]], 0, 0, 0, implicit $exec
+  ; CHECK:   [[DEF2]].sub0:vreg_64 = GLOBAL_LOAD_DWORD [[DEF3]], 0, 0, 0, implicit $exec
+  ; CHECK:   dead %20:vgpr_32 = GLOBAL_LOAD_DWORD %11, 0, 0, 0, implicit $exec
+  ; CHECK:   dead %21:vgpr_32 = GLOBAL_LOAD_DWORD [[DEF4]], 0, 0, 0, implicit $exec
+  ; CHECK:   [[V_LSHLREV_B64_:%[0-9]+]]:vreg_64 = V_LSHLREV_B64 2, [[DEF2]], implicit $exec
+  ; CHECK:   dead %22:vgpr_32 = GLOBAL_LOAD_DWORD [[DEF5]], 0, 0, 0, implicit $exec
+  ; CHECK:   S_NOP 0, implicit [[DEF7]], implicit [[V_LSHLREV_B64_]].sub0, implicit [[DEF6]], implicit [[V_MOV_B32_e32_]]
+  ; CHECK:   GLOBAL_STORE_DWORD [[DEF5]], [[V_MOV_B32_e32_1]], 0, 0, 0, implicit $exec
+  ; CHECK: bb.1:
+  ; CHECK:   successors: %bb.2(0x80000000)
+  ; CHECK:   S_SETREG_IMM32_B32 0, 1
+  ; CHECK:   DBG_VALUE
+  ; CHECK:   DBG_VALUE
+  ; CHECK:   DBG_VALUE
+  ; CHECK:   S_SETREG_IMM32_B32 0, 1
+  ; CHECK: bb.2:
+  ; CHECK:   S_NOP 0, implicit [[COPY]]
+  ; CHECK:   S_NOP 0, implicit [[DEF8]]
+  ; CHECK:   S_ENDPGM 0
+  bb.0:
+    liveins: $vgpr0
+
+    %0:vgpr_32 = COPY $vgpr0
+    %1:vreg_64 = IMPLICIT_DEF
+    %2:vreg_64 = GLOBAL_LOAD_DWORDX2 %1, 0, 0, 0, implicit $exec
+    %3:vgpr_32 = GLOBAL_LOAD_DWORD %1, 8, 0, 0, implicit $exec
+    undef %4.sub1:vreg_64 = V_ADD_U32_e32 %0, %0, implicit $exec
+    %4.sub0:vreg_64 = V_MOV_B32_e32 111, implicit $exec
+    %5:vreg_64 = COPY %2
+    undef %6.sub0:vreg_64 = V_ADD_F32_e32 %1.sub0, %5.sub0, implicit $exec
+    %6.sub1:vreg_64 = V_ADD_F32_e32 %1.sub1, %5.sub0, implicit $exec
+    %7:vgpr_32 = GLOBAL_LOAD_DWORD %5, 0, 0, 0, implicit $exec
+    %8:vreg_64 = IMPLICIT_DEF
+    %9:vreg_64 = IMPLICIT_DEF
+    %10:vreg_64 = IMPLICIT_DEF
+    undef %11.sub1:vreg_64 = IMPLICIT_DEF
+    %12:vgpr_32 = IMPLICIT_DEF
+    %13:vgpr_32 = IMPLICIT_DEF
+    %14:vreg_64 = IMPLICIT_DEF
+    %15:vreg_64 = IMPLICIT_DEF
+    %16:vgpr_32 = IMPLICIT_DEF
+    %17:vgpr_32 = V_MOV_B32_e32 0, implicit $exec
+    %18:vgpr_32 = V_MOV_B32_e32 0, implicit $exec
+    undef %19.sub0:vreg_64 = V_ADD_F32_e32 %7, %2.sub0, implicit $exec
+    %19.sub1:vreg_64 = V_ADD_F32_e32 %3, %3, implicit $exec
+    GLOBAL_STORE_DWORDX2 %19, %4, 32, 0, 0, implicit $exec
+    %11.sub0:vreg_64 = GLOBAL_LOAD_DWORD %9, 0, 0, 0, implicit $exec
+    %8.sub0:vreg_64 = GLOBAL_LOAD_DWORD %10, 0, 0, 0, implicit $exec
+    %20:vgpr_32 = GLOBAL_LOAD_DWORD %11, 0, 0, 0, implicit $exec
+    %21:vgpr_32 = GLOBAL_LOAD_DWORD %14, 0, 0, 0, implicit $exec
+    %22:vgpr_32 = GLOBAL_LOAD_DWORD %15, 0, 0, 0, implicit $exec
+    %23:vreg_64 = V_LSHLREV_B64 2, %8, implicit $exec
+    S_NOP 0, implicit %13, implicit %23.sub0, implicit %12, implicit %17
+    GLOBAL_STORE_DWORD %15, %18, 0, 0, 0, implicit $exec
+
+  bb.1:
+    S_SETREG_IMM32_B32 0, 1
+    DBG_VALUE
+    DBG_VALUE
+    DBG_VALUE
+    S_SETREG_IMM32_B32 0, 1
+
+  bb.2:
+    S_NOP 0, implicit %0
+    S_NOP 0, implicit %16
+    S_ENDPGM 0
+
+...