From a58da1a2ff039dd3bb4c43db3919995cf4a74cc7 Mon Sep 17 00:00:00 2001
From: Alexey Bataev <a.bataev@hotmail.com>
Date: Fri, 27 Dec 2019 09:44:43 -0500
Subject: [OPENMP50]Codegen for lastprivate conditional list items.

Added codegen support for lastprivate conditional. According to the
standard, if  when the conditional modifier appears on the clause, if an
assignment to a list item is encountered in the construct then the
original list item is assigned the value that is assigned to the new
list item in the sequentially last iteration or lexically last section
in which such an assignment is encountered.
We look for the assignment operations and check if the left side
references lastprivate conditional variable. Then the next code is
emitted:
if (last_iv_a <= iv) {
  last_iv_a = iv;
  last_a = lp_a;
}

At the end the implicit barrier is generated to wait for the end of all
threads and then in the check for the last iteration the private copy is
assigned the last value.

if (last_iter) {
  lp_a = last_a; // <--- new code
  a = lp_a;      // <--- store of private value to the original  variable.
}
---
 clang/lib/CodeGen/CGStmtOpenMP.cpp | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

(limited to 'clang/lib/CodeGen/CGStmtOpenMP.cpp')

diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index a38a79b6454..cac0e7d4ed6 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -1045,6 +1045,18 @@ void CodeGenFunction::EmitOMPLastprivateClauseFinal(
   llvm::BasicBlock *ThenBB = nullptr;
   llvm::BasicBlock *DoneBB = nullptr;
   if (IsLastIterCond) {
+    // Emit implicit barrier if at least one lastprivate conditional is found
+    // and this is not a simd mode.
+    if (!getLangOpts().OpenMPSimd &&
+        llvm::any_of(D.getClausesOfKind<OMPLastprivateClause>(),
+                     [](const OMPLastprivateClause *C) {
+                       return C->getKind() == OMPC_LASTPRIVATE_conditional;
+                     })) {
+      CGM.getOpenMPRuntime().emitBarrierCall(*this, D.getBeginLoc(),
+                                             OMPD_unknown,
+                                             /*EmitChecks=*/false,
+                                             /*ForceSimpleCall=*/true);
+    }
     ThenBB = createBasicBlock(".omp.lastprivate.then");
     DoneBB = createBasicBlock(".omp.lastprivate.done");
     Builder.CreateCondBr(IsLastIterCond, ThenBB, DoneBB);
@@ -1083,14 +1095,19 @@ void CodeGenFunction::EmitOMPLastprivateClauseFinal(
             cast<VarDecl>(cast<DeclRefExpr>(*ISrcRef)->getDecl());
         const auto *DestVD =
             cast<VarDecl>(cast<DeclRefExpr>(*IDestRef)->getDecl());
-        // Get the address of the original variable.
-        Address OriginalAddr = GetAddrOfLocalVar(DestVD);
         // Get the address of the private variable.
         Address PrivateAddr = GetAddrOfLocalVar(PrivateVD);
         if (const auto *RefTy = PrivateVD->getType()->getAs<ReferenceType>())
           PrivateAddr =
               Address(Builder.CreateLoad(PrivateAddr),
                       getNaturalTypeAlignment(RefTy->getPointeeType()));
+        // Store the last value to the private copy in the last iteration.
+        if (C->getKind() == OMPC_LASTPRIVATE_conditional)
+          CGM.getOpenMPRuntime().emitLastprivateConditionalFinalUpdate(
+              *this, MakeAddrLValue(PrivateAddr, (*IRef)->getType()), PrivateVD,
+              (*IRef)->getExprLoc());
+        // Get the address of the original variable.
+        Address OriginalAddr = GetAddrOfLocalVar(DestVD);
         EmitOMPCopy(Type, OriginalAddr, PrivateAddr, DestVD, SrcVD, AssignOp);
       }
       ++IRef;
@@ -1974,6 +1991,8 @@ static void emitOMPSimdRegion(CodeGenFunction &CGF, const OMPLoopDirective &S,
     CGF.EmitOMPLinearClause(S, LoopScope);
     CGF.EmitOMPPrivateClause(S, LoopScope);
     CGF.EmitOMPReductionClauseInit(S, LoopScope);
+    CGOpenMPRuntime::LastprivateConditionalRAII LPCRegion(
+        CGF, S, CGF.EmitLValue(S.getIterationVariable()));
     bool HasLastprivateClause = CGF.EmitOMPLastprivateClauseInit(S, LoopScope);
     (void)LoopScope.Privatize();
     if (isOpenMPTargetExecutionDirective(S.getDirectiveKind()))
@@ -2546,6 +2565,8 @@ bool CodeGenFunction::EmitOMPWorksharingLoop(
             /*ForceSimpleCall=*/true);
       }
       EmitOMPPrivateClause(S, LoopScope);
+      CGOpenMPRuntime::LastprivateConditionalRAII LPCRegion(
+          *this, S, EmitLValue(S.getIterationVariable()));
       HasLastprivateClause = EmitOMPLastprivateClauseInit(S, LoopScope);
       EmitOMPReductionClauseInit(S, LoopScope);
       EmitOMPPrivateLoopCounters(S, LoopScope);
@@ -2856,6 +2877,7 @@ void CodeGenFunction::EmitSections(const OMPExecutableDirective &S) {
           /*ForceSimpleCall=*/true);
     }
     CGF.EmitOMPPrivateClause(S, LoopScope);
+    CGOpenMPRuntime::LastprivateConditionalRAII LPCRegion(CGF, S, IV);
     HasLastprivates = CGF.EmitOMPLastprivateClauseInit(S, LoopScope);
     CGF.EmitOMPReductionClauseInit(S, LoopScope);
     (void)LoopScope.Privatize();
-- 
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