LoopVersioningLICM: Respect convergent

[Meinersbur]

LGTM

lib/Transforms/Scalar/LoopVersioningLICM.cpp

356–358

Could you update the function's comment?

[arsenm]

r362031

lib/Transforms/Scalar/LoopVersioningLICM.cpp

if (!HasMayAlias) {
     return false;
   }
   return true;
 }
 
 /// Check loop instructions safe for Loop versioning.
 /// It returns true if it's safe else returns false.
 /// Consider following:
 /// 1) Check all load store in loop body are non atomic & non volatile.
 /// 2) Check function call safety, by ensuring its not accessing memory.
 /// 3) Loop body shouldn't have any may throw instruction.
 bool LoopVersioningLICM::instructionSafeForVersioning(Instruction *I) {
   assert(I != nullptr && "Null instruction found!");
   // Check function call safety
-  if (auto *Call = dyn_cast<CallBase>(I))
+  if (auto *Call = dyn_cast<CallBase>(I)) {
+    if (Call->isConvergent() || Call->cannotDuplicate()) {
+      LLVM_DEBUG(dbgs() << "    Convergent call site found.\n");
+      return false;
+    }
+
     if (!AA->doesNotAccessMemory(Call)) {
       LLVM_DEBUG(dbgs() << "    Unsafe call site found.\n");
       return false;
     }
+  }
+
   // Avoid loops with possiblity of throw
   if (I->mayThrow()) {
     LLVM_DEBUG(dbgs() << "    May throw instruction found in loop body\n");
     return false;
   }
   // If current instruction is load instructions
   // make sure it's a simple load (non atomic & non volatile)
   if (I->mayReadFromMemory()) {

test/Transforms/LoopVersioningLICM/convergent.ll

+; RUN: opt -S -loop-versioning-licm -licm-versioning-invariant-threshold=0 %s | FileCheck %s
+
+; Make sure the convergent attribute is respected, and no condition is
+; introduced
+
+; CHECK-LABEL: @test_convergent(
+; CHECK: call void @llvm.convergent()
+; CHECK-NOT: call void @llvm.convergent()
+define i32 @test_convergent(i32* nocapture %var1, i32* nocapture readnone %var2, i32* nocapture %var3, i32 %itr) #1 {
+entry:
+  %cmp14 = icmp eq i32 %itr, 0
+  br i1 %cmp14, label %for.end13, label %for.cond1.preheader
+
+for.cond1.preheader:                              ; preds = %entry, %for.inc11
+  %j.016 = phi i32 [ %j.1.lcssa, %for.inc11 ], [ 0, %entry ]
+  %i.015 = phi i32 [ %inc12, %for.inc11 ], [ 0, %entry ]
+  %cmp212 = icmp ult i32 %j.016, %itr
+  br i1 %cmp212, label %for.body3.lr.ph, label %for.inc11
+
+for.body3.lr.ph:                                  ; preds = %for.cond1.preheader
+  %add = add i32 %i.015, %itr
+  %idxprom6 = zext i32 %i.015 to i64
+  %arrayidx7 = getelementptr inbounds i32, i32* %var3, i64 %idxprom6
+  br label %for.body3
+
+for.body3:                                        ; preds = %for.body3, %for.body3.lr.ph
+  %j.113 = phi i32 [ %j.016, %for.body3.lr.ph ], [ %inc, %for.body3 ]
+  %idxprom = zext i32 %j.113 to i64
+  %arrayidx = getelementptr inbounds i32, i32* %var1, i64 %idxprom
+  store i32 %add, i32* %arrayidx, align 4
+  %load.arrayidx7 = load i32, i32* %arrayidx7, align 4
+  call void @llvm.convergent()
+  %add8 = add nsw i32 %load.arrayidx7, %add
+  store i32 %add8, i32* %arrayidx7, align 4
+  %inc = add nuw i32 %j.113, 1
+  %cmp2 = icmp ult i32 %inc, %itr
+  br i1 %cmp2, label %for.body3, label %for.inc11
+
+for.inc11:                                        ; preds = %for.body3, %for.cond1.preheader
+  %j.1.lcssa = phi i32 [ %j.016, %for.cond1.preheader ], [ %itr, %for.body3 ]
+  %inc12 = add nuw i32 %i.015, 1
+  %cmp = icmp ult i32 %inc12, %itr
+  br i1 %cmp, label %for.cond1.preheader, label %for.end13
+
+for.end13:                                        ; preds = %for.inc11, %entry
+  ret i32 0
+}
+
+; CHECK-LABEL: @test_noduplicate(
+; CHECK: call void @llvm.noduplicate()
+; CHECK-NOT: call void @llvm.noduplicate()
+define i32 @test_noduplicate(i32* nocapture %var1, i32* nocapture readnone %var2, i32* nocapture %var3, i32 %itr) #2 {
+entry:
+  %cmp14 = icmp eq i32 %itr, 0
+  br i1 %cmp14, label %for.end13, label %for.cond1.preheader
+
+for.cond1.preheader:                              ; preds = %entry, %for.inc11
+  %j.016 = phi i32 [ %j.1.lcssa, %for.inc11 ], [ 0, %entry ]
+  %i.015 = phi i32 [ %inc12, %for.inc11 ], [ 0, %entry ]
+  %cmp212 = icmp ult i32 %j.016, %itr
+  br i1 %cmp212, label %for.body3.lr.ph, label %for.inc11
+
+for.body3.lr.ph:                                  ; preds = %for.cond1.preheader
+  %add = add i32 %i.015, %itr
+  %idxprom6 = zext i32 %i.015 to i64
+  %arrayidx7 = getelementptr inbounds i32, i32* %var3, i64 %idxprom6
+  br label %for.body3
+
+for.body3:                                        ; preds = %for.body3, %for.body3.lr.ph
+  %j.113 = phi i32 [ %j.016, %for.body3.lr.ph ], [ %inc, %for.body3 ]
+  %idxprom = zext i32 %j.113 to i64
+  %arrayidx = getelementptr inbounds i32, i32* %var1, i64 %idxprom
+  store i32 %add, i32* %arrayidx, align 4
+  %load.arrayidx7 = load i32, i32* %arrayidx7, align 4
+  call void @llvm.noduplicate()
+  %add8 = add nsw i32 %load.arrayidx7, %add
+  store i32 %add8, i32* %arrayidx7, align 4
+  %inc = add nuw i32 %j.113, 1
+  %cmp2 = icmp ult i32 %inc, %itr
+  br i1 %cmp2, label %for.body3, label %for.inc11
+
+for.inc11:                                        ; preds = %for.body3, %for.cond1.preheader
+  %j.1.lcssa = phi i32 [ %j.016, %for.cond1.preheader ], [ %itr, %for.body3 ]
+  %inc12 = add nuw i32 %i.015, 1
+  %cmp = icmp ult i32 %inc12, %itr
+  br i1 %cmp, label %for.cond1.preheader, label %for.end13
+
+for.end13:                                        ; preds = %for.inc11, %entry
+  ret i32 0
+}
+
+declare void @llvm.convergent() #1
+declare void @llvm.noduplicate() #2
+
+attributes #0 = { norecurse nounwind }
+attributes #1 = { norecurse nounwind readnone convergent }
+attributes #2 = { norecurse nounwind readnone noduplicate }