[Pipeliner] Fix incorrect phi values in the epilog and kernel

The code that generates the loop definition operand for phis
in the epilog and kernel is incorrect in some cases.

In the kernel, when a phi refers to another phi, the code that
updates PhiOp2 needs to include the stage difference between
the two phis.

In the epilog, the check for using the loop definition instead
of the phi definition uses the StageDiffAdj value (the difference
between the phi stage and the loop definition stage), but the
adjustment is not needed to determine if the current stage
contains an iteration with the loop definition.

Differential Revision: https://reviews.llvm.org/D51167

llvm-svn: 340782

1 files changed, 32 insertions, 29 deletions

diff --git a/llvm/lib/CodeGen/MachinePipeliner.cpp b/llvm/lib/CodeGen/MachinePipeliner.cpp
index c8d2c492b98..a02669aa4e2 100644
--- a/llvm/lib/CodeGen/MachinePipeliner.cpp
+++ b/llvm/lib/CodeGen/MachinePipeliner.cpp
@@ -2725,7 +2725,7 @@ void SwingSchedulerDAG::generateExistingPhis(
                  VRMap[PrevStage - np + 1].count(Def))
           PhiOp2 = VRMap[PrevStage - np + 1][Def];
         // Use the loop value defined in the kernel.
-        else if ((unsigned)LoopValStage + StageDiffAdj > PrologStage + 1 &&
+        else if (static_cast<unsigned>(LoopValStage) > PrologStage + 1 &&
                  VRMap[PrevStage - StageDiffAdj - np].count(LoopVal))
           PhiOp2 = VRMap[PrevStage - StageDiffAdj - np][LoopVal];
         // Use the value defined by the Phi, unless we're generating the first
@@ -2739,35 +2739,38 @@ void SwingSchedulerDAG::generateExistingPhis(
       // references another Phi, and the other Phi is scheduled in an
       // earlier stage. We can try to reuse an existing Phi up until the last
       // stage of the current Phi.
-      if (LoopDefIsPhi && (int)(PrologStage - np) >= StageScheduled) {
-        int LVNumStages = Schedule.getStagesForPhi(LoopVal);
-        int StageDiff = (StageScheduled - LoopValStage);
-        LVNumStages -= StageDiff;
-        // Make sure the loop value Phi has been processed already.
-        if (LVNumStages > (int)np && VRMap[CurStageNum].count(LoopVal)) {
-          NewReg = PhiOp2;
-          unsigned ReuseStage = CurStageNum;
-          if (Schedule.isLoopCarried(this, *PhiInst))
-            ReuseStage -= LVNumStages;
-          // Check if the Phi to reuse has been generated yet. If not, then
-          // there is nothing to reuse.
-          if (VRMap[ReuseStage - np].count(LoopVal)) {
-            NewReg = VRMap[ReuseStage - np][LoopVal];
-
-            rewriteScheduledInstr(NewBB, Schedule, InstrMap, CurStageNum, np,
-                                  &*BBI, Def, NewReg);
-            // Update the map with the new Phi name.
-            VRMap[CurStageNum - np][Def] = NewReg;
-            PhiOp2 = NewReg;
-            if (VRMap[LastStageNum - np - 1].count(LoopVal))
-              PhiOp2 = VRMap[LastStageNum - np - 1][LoopVal];
-
-            if (IsLast && np == NumPhis - 1)
-              replaceRegUsesAfterLoop(Def, NewReg, BB, MRI, LIS);
-            continue;
+      if (LoopDefIsPhi) {
+        if (static_cast<int>(PrologStage - np) >= StageScheduled) {
+          int LVNumStages = Schedule.getStagesForPhi(LoopVal);
+          int StageDiff = (StageScheduled - LoopValStage);
+          LVNumStages -= StageDiff;
+          // Make sure the loop value Phi has been processed already.
+          if (LVNumStages > (int)np && VRMap[CurStageNum].count(LoopVal)) {
+            NewReg = PhiOp2;
+            unsigned ReuseStage = CurStageNum;
+            if (Schedule.isLoopCarried(this, *PhiInst))
+              ReuseStage -= LVNumStages;
+            // Check if the Phi to reuse has been generated yet. If not, then
+            // there is nothing to reuse.
+            if (VRMap[ReuseStage - np].count(LoopVal)) {
+              NewReg = VRMap[ReuseStage - np][LoopVal];
+
+              rewriteScheduledInstr(NewBB, Schedule, InstrMap, CurStageNum, np,
+                                    &*BBI, Def, NewReg);
+              // Update the map with the new Phi name.
+              VRMap[CurStageNum - np][Def] = NewReg;
+              PhiOp2 = NewReg;
+              if (VRMap[LastStageNum - np - 1].count(LoopVal))
+                PhiOp2 = VRMap[LastStageNum - np - 1][LoopVal];
+
+              if (IsLast && np == NumPhis - 1)
+                replaceRegUsesAfterLoop(Def, NewReg, BB, MRI, LIS);
+              continue;
+            }
           }
-        } else if (InKernel && StageDiff > 0 &&
-                   VRMap[CurStageNum - StageDiff - np].count(LoopVal))
+        }
+        if (InKernel && StageDiff > 0 &&
+            VRMap[CurStageNum - StageDiff - np].count(LoopVal))
           PhiOp2 = VRMap[CurStageNum - StageDiff - np][LoopVal];
       }