[llvm] r365428 - [MachinePipeliner] Fix Phi refers to Phi in same stage in 1st epilogue

[Jinsong Ji via llvm-commits]

Author: jsji
Date: Mon Jul  8 19:27:35 2019
New Revision: 365428

URL: http://llvm.org/viewvc/llvm-project?rev=365428&view=rev
Log:
[MachinePipeliner] Fix Phi refers to Phi in same stage in 1st epilogue

Summary:
This is exposed by functional testing on PowerPC.
In some pipelined loops, Phi refer to phi did not get value defined by
the Phi, hence getting wrong value later.

As the comment mentioned, we should "use the value defined by the Phi,
unless we're generating the firstepilog and the Phi refers to a Phi
 in a different stage.", so Phi refering to same stage Phi should use
the value defined by the Phi here.

Reviewers: bcahoon, hfinkel

Reviewed By: hfinkel

Subscribers: MaskRay, wuzish, nemanjai, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64035

Modified:
    llvm/trunk/lib/CodeGen/MachinePipeliner.cpp
    llvm/trunk/test/CodeGen/PowerPC/sms-phi.ll

Modified: llvm/trunk/lib/CodeGen/MachinePipeliner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachinePipeliner.cpp?rev=365428&r1=365427&r2=365428&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachinePipeliner.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachinePipeliner.cpp Mon Jul  8 19:27:35 2019
@@ -2430,7 +2430,7 @@ void SwingSchedulerDAG::generateExisting
         // Use the value defined by the Phi, unless we're generating the first
         // epilog and the Phi refers to a Phi in a different stage.
         else if (VRMap[PrevStage - np].count(Def) &&
-                 (!LoopDefIsPhi || PrevStage != LastStageNum))
+                 (!LoopDefIsPhi || (PrevStage != LastStageNum) || (LoopValStage == StageScheduled)))
           PhiOp2 = VRMap[PrevStage - np][Def];
       }
 

Modified: llvm/trunk/test/CodeGen/PowerPC/sms-phi.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/sms-phi.ll?rev=365428&r1=365427&r2=365428&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/sms-phi.ll (original)
+++ llvm/trunk/test/CodeGen/PowerPC/sms-phi.ll Mon Jul  8 19:27:35 2019
@@ -8,7 +8,7 @@ define dso_local void @sha512() #0 {
 ;CHECK: epilog:
 ;CHECK:        %23:g8rc_and_g8rc_nox0 = PHI %5:g8rc_and_g8rc_nox0, %bb.3, %18:g8rc_and_g8rc_nox0, %bb.4
 ;CHECK-NEXT:   %24:g8rc = PHI %6:g8rc, %bb.3, %16:g8rc, %bb.4
-;CHECK-NEXT:   %25:g8rc = PHI %6:g8rc, %bb.3, %16:g8rc, %bb.4
+;CHECK-NEXT:   %25:g8rc = PHI %6:g8rc, %bb.3, %19:g8rc, %bb.4
   br label %1
 
 1:                                                ; preds = %1, %0