[llvm] r365216 - ScheduleDAG: Fix incorrectly killing registers in bundles

[Matt Arsenault via llvm-commits]

Author: arsenm
Date: Fri Jul  5 08:32:28 2019
New Revision: 365216

URL: http://llvm.org/viewvc/llvm-project?rev=365216&view=rev
Log:
ScheduleDAG: Fix incorrectly killing registers in bundles

When looking for uses/defs to add kill flags, the iterator was double
incremented, skipping the first instruction in the bundle. The use
register in the first bundle instruction was then incorrectly killed.
The "First" instruction should be the BUNDLE itself as the proper
reverse iterator endpoint.

Added:
    llvm/trunk/test/CodeGen/AMDGPU/post-ra-sched-kill-bundle-use-inst.mir
Modified:
    llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp

Modified: llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp?rev=365216&r1=365215&r2=365216&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp (original)
+++ llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp Fri Jul  5 08:32:28 2019
@@ -1104,22 +1104,21 @@ void ScheduleDAGInstrs::fixupKills(Machi
     if (!MI.isBundled()) {
       toggleKills(MRI, LiveRegs, MI, true);
     } else {
-      MachineBasicBlock::instr_iterator First = MI.getIterator();
-      if (MI.isBundle()) {
+      MachineBasicBlock::instr_iterator Bundle = MI.getIterator();
+      if (MI.isBundle())
         toggleKills(MRI, LiveRegs, MI, false);
-        ++First;
-      }
+
       // Some targets make the (questionable) assumtion that the instructions
       // inside the bundle are ordered and consequently only the last use of
       // a register inside the bundle can kill it.
-      MachineBasicBlock::instr_iterator I = std::next(First);
+      MachineBasicBlock::instr_iterator I = std::next(Bundle);
       while (I->isBundledWithSucc())
         ++I;
       do {
         if (!I->isDebugInstr())
           toggleKills(MRI, LiveRegs, *I, true);
         --I;
-      } while(I != First);
+      } while (I != Bundle);
     }
   }
 }

Added: llvm/trunk/test/CodeGen/AMDGPU/post-ra-sched-kill-bundle-use-inst.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AMDGPU/post-ra-sched-kill-bundle-use-inst.mir?rev=365216&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AMDGPU/post-ra-sched-kill-bundle-use-inst.mir (added)
+++ llvm/trunk/test/CodeGen/AMDGPU/post-ra-sched-kill-bundle-use-inst.mir Fri Jul  5 08:32:28 2019
@@ -0,0 +1,42 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=amdgcn-mesa-mesa3d -mcpu=gfx900 -run-pass=post-RA-sched -verify-machineinstrs -o -  %s | FileCheck %s
+
+# The scheduler was not inspecting the first instruction in the bundle
+# when adding kill flags, so it would incorrectly mark the first use
+# of $vgpr0 as killed.
+
+---
+name: kill_flag_use_first_bundle_inst
+tracksRegLiveness: true
+machineFunctionInfo:
+  isEntryFunction: true
+body:             |
+  bb.0:
+    liveins: $sgpr4_sgpr5, $sgpr7
+
+    ; CHECK-LABEL: name: kill_flag_use_first_bundle_inst
+    ; CHECK: liveins: $sgpr4_sgpr5, $sgpr7
+    ; CHECK: renamable $sgpr0 = S_LOAD_DWORD_IMM killed renamable $sgpr4_sgpr5, 0, 0, 0
+    ; CHECK: $m0 = S_MOV_B32 -1
+    ; CHECK: $vgpr0 = V_MOV_B32_e32 killed $sgpr0, implicit $exec, implicit $exec
+    ; CHECK: BUNDLE implicit $vgpr0, implicit $m0, implicit $exec {
+    ; CHECK:   DS_GWS_INIT $vgpr0, 8, -1, implicit $m0, implicit $exec
+    ; CHECK:   S_WAITCNT 0
+    ; CHECK: }
+    ; CHECK: BUNDLE implicit killed $vgpr0, implicit $m0, implicit $exec {
+    ; CHECK:   DS_GWS_BARRIER killed $vgpr0, 8, -1, implicit $m0, implicit $exec
+    ; CHECK:   S_WAITCNT 0
+    ; CHECK: }
+    renamable $sgpr0 = S_LOAD_DWORD_IMM killed renamable $sgpr4_sgpr5, 0, 0, 0
+    $m0 = S_MOV_B32 -1
+    $vgpr0 = V_MOV_B32_e32 $sgpr0, implicit $exec, implicit $exec
+    BUNDLE implicit $vgpr0, implicit $m0, implicit $exec {
+      DS_GWS_INIT $vgpr0, 8, -1, implicit $m0, implicit $exec
+      S_WAITCNT 0
+    }
+    BUNDLE implicit killed $vgpr0, implicit $m0, implicit $exec {
+      DS_GWS_BARRIER $vgpr0, 8, -1, implicit $m0, implicit $exec
+      S_WAITCNT 0
+    }
+
+...