[LoopVectorize] Change comment for isOutOfScope in collectLoopUniforms, NFC

[wmi]

Summary

Update comment for isOutOfScope.
Add a testcase for uniform value being used out of scope.

[mkuper]

LGTM with two tiny nits.

lib/Transforms/Vectorize/LoopVectorize.cpp

4949

As long as you're changing this, can we change "variables" to something more meaningful? Instructions, or perhaps values?

4952

Maybe "Global values, params and instructions outside of the current loop are"?

[wmi]

Thanks for the review.

lib/Transforms/Vectorize/LoopVectorize.cpp

4949

I change variables to instructions.

4952

Fixed.

lib/Transforms/Vectorize/LoopVectorize.cpp

for (auto &Induction : *getInductionVars()) {
     // The induction variable and its update instruction will remain scalar.
     Scalars.insert(Ind);
     Scalars.insert(IndUpdate);
   }
 }
 
 void LoopVectorizationLegality::collectLoopUniforms() {
   // We now know that the loop is vectorizable!
-  // Collect variables that will remain uniform after vectorization.
+  // Collect variables inside the loop that will remain uniform after
+  // vectorization.
 
-  // If V is not an instruction inside the current loop, it is a Value
-  // outside of the scope which we are interesting in.
+  // Global value, param or instruction outside of current loop are out of
+  // scope.
   auto isOutOfScope = [&](Value *V) -> bool {
     Instruction *I = dyn_cast<Instruction>(V);
     return (!I || !TheLoop->contains(I));
   };
 
   SetVector<Instruction *> Worklist;
   BasicBlock *Latch = TheLoop->getLoopLatch();
   // Start with the conditional branch.

test/Transforms/LoopVectorize/X86/uniform-phi.ll

for.body:
   store i32 %tmp0, i32* %tmp1, align 4
   %i.next = add nuw nsw i64 %i, 1
   %cond = icmp eq i64 %i.next, %n
   br i1 %cond, label %for.end, label %for.body
 
 for.end:
   ret void
 }
+
+; CHECK-LABEL: goo
+; Check %indvars.iv and %indvars.iv.next are uniform instructions even if they are used outside of loop.
+; CHECK-DAG: LV: Found uniform instruction:   %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+; CHECK-DAG: LV: Found uniform instruction:   %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+; CHECK-DAG: LV: Found uniform instruction:   %exitcond = icmp eq i64 %indvars.iv, 1599
+
+define i64 @goo(float* noalias nocapture %a, float* noalias nocapture readonly %b) #0 {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %arrayidx = getelementptr inbounds float, float* %b, i64 %indvars.iv
+  %tmp0 = load float, float* %arrayidx, align 4
+  %add = fadd float %tmp0, 1.000000e+00
+  %arrayidx5 = getelementptr inbounds float, float* %a, i64 %indvars.iv
+  store float %add, float* %arrayidx5, align 4
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv, 1599
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body
+  %retval = add i64 %indvars.iv, %indvars.iv.next
+  ret i64 %retval
+}
+