[PATCH] D75101: [OpenMP] Fix insertion point for deduplicated runtime call to honor def-use order

[Wenlei He via Phabricator via llvm-commits]

wenlei created this revision.
wenlei added reviewers: jdoerfert, JonChesterfield, hoyFB.
Herald added subscribers: llvm-commits, guansong, hiraditya.
Herald added a project: LLVM.

A recently added OpenMP optimization pass (D69930 <https://reviews.llvm.org/D69930>) tries to deduplicate omp runtime calls by merging the calls and insert a new one in entry block. However the insertion didn't honor def-use chain of parameters, so it can introduce use-before-def. This change fixed the problem by taking def-use into account for finding insertion point of the merged runtime call.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D75101

Files:
  llvm/lib/Transforms/IPO/OpenMPOpt.cpp
  llvm/test/Transforms/OpenMP/gtid.ll


Index: llvm/test/Transforms/OpenMP/gtid.ll
===================================================================
--- llvm/test/Transforms/OpenMP/gtid.ll
+++ llvm/test/Transforms/OpenMP/gtid.ll
@@ -15,7 +15,8 @@
 ; CHECK-LABEL: define {{[^@]+}}@external
 ; CHECK-SAME: (i1 [[C:%.*]])
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[C2:%.*]] = tail call i32 @__kmpc_global_thread_num(%struct.ident_t* nonnull @0)
+; CHECK-NEXT:    %tmp1 = alloca %struct.ident_t
+; CHECK-NEXT:    [[C2:%.*]] = tail call i32 @__kmpc_global_thread_num(%struct.ident_t* nonnull %tmp1)
 ; CHECK-NEXT:    br i1 [[C]], label [[T:%.*]], label [[E:%.*]]
 ; CHECK:       t:
 ; CHECK-NEXT:    call void @internal(i32 [[C2]], i32 [[C2]])
@@ -31,19 +32,20 @@
 ; CHECK-NEXT:    ret void
 ;
 entry:
+  %tmp1 = alloca %struct.ident_t, align 8
   br i1 %c, label %t, label %e
 t:
-  %c0 = tail call i32 @__kmpc_global_thread_num(%struct.ident_t* nonnull @0)
+  %c0 = tail call i32 @__kmpc_global_thread_num(%struct.ident_t* nonnull %tmp1)
   call void @internal(i32 %c0, i32 %c0)
   call void @useI32(i32 %c0)
   br label %m
 e:
-  %c1 = tail call i32 @__kmpc_global_thread_num(%struct.ident_t* nonnull @0)
+  %c1 = tail call i32 @__kmpc_global_thread_num(%struct.ident_t* nonnull %tmp1)
   call void @internal(i32 %c1, i32 %c1)
   call void @useI32(i32 %c1)
   br label %m
 m:
-  %c2 = tail call i32 @__kmpc_global_thread_num(%struct.ident_t* nonnull @0)
+  %c2 = tail call i32 @__kmpc_global_thread_num(%struct.ident_t* nonnull %tmp1)
   call void @internal(i32 0, i32 %c2)
   call void @useI32(i32 %c2)
   ret void
Index: llvm/lib/Transforms/IPO/OpenMPOpt.cpp
===================================================================
--- llvm/lib/Transforms/IPO/OpenMPOpt.cpp
+++ llvm/lib/Transforms/IPO/OpenMPOpt.cpp
@@ -219,7 +219,16 @@
     if (!ReplVal) {
       for (Use *U : Uses)
         if (CallInst *CI = getCallIfRegularCall(*U, &RFI)) {
-          CI->moveBefore(&*F.getEntryBlock().getFirstInsertionPt());
+          Value *Op0 = CI->getOperand(0);
+          Instruction *MovePt = &*F.getEntryBlock().getFirstInsertionPt();
+          if (Instruction *DefInst = dyn_cast<Instruction>(Op0)) {
+            if (DefInst->getParent() != &F.getEntryBlock())
+              break;
+            if (!DefInst->comesBefore(MovePt)) {
+              MovePt = DefInst->getNextNode();
+            }
+          }
+          CI->moveBefore(MovePt);
           ReplVal = CI;
           break;
         }


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