[DA] Improve dump to show source and sink of the dependence

Summary:
The current da printer shows the dependence without indicating
which instructions are being considered as the src vs dst. It
also silently ignores call instructions, despite the fact that
they create confused dependence edges to other memory
instructions. This patch addresses these two issues plus a
couple of minor non-functional improvements.

Authored By: bmahjour

Reviewer: dmgreen, fhahn, philip.pfaffe, chandlerc

Reviewed By: dmgreen, fhahn

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71088

llvm/lib/Analysis/DependenceAnalysis.cpp

@@ -170,25 +170,25 @@ void DependenceAnalysisWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequiredTransitive<LoopInfoWrapperPass>();
 }
 
-
 // Used to test the dependence analyzer.
-// Looks through the function, noting loads and stores.
+// Looks through the function, noting instructions that may access memory.
 // Calls depends() on every possible pair and prints out the result.
 // Ignores all other instructions.
 static void dumpExampleDependence(raw_ostream &OS, DependenceInfo *DA) {
   auto *F = DA->getFunction();
   for (inst_iterator SrcI = inst_begin(F), SrcE = inst_end(F); SrcI != SrcE;
        ++SrcI) {
-    if (isa<StoreInst>(*SrcI) || isa<LoadInst>(*SrcI)) {
+    if (SrcI->mayReadOrWriteMemory()) {
       for (inst_iterator DstI = SrcI, DstE = inst_end(F);
            DstI != DstE; ++DstI) {
-        if (isa<StoreInst>(*DstI) || isa<LoadInst>(*DstI)) {
-          OS << "da analyze - ";
+        if (DstI->mayReadOrWriteMemory()) {
+          OS << "Src:" << *SrcI << " --> Dst:" << *DstI << "\n";
+          OS << "  da analyze - ";
           if (auto D = DA->depends(&*SrcI, &*DstI, true)) {
             D->dump(OS);
             for (unsigned Level = 1; Level <= D->getLevels(); Level++) {
               if (D->isSplitable(Level)) {
-                OS << "da analyze - split level = " << Level;
+                OS << "  da analyze - split level = " << Level;
                 OS << ", iteration = " << *DA->getSplitIteration(*D, Level);
                 OS << "!\n";
               }
@@ -3413,8 +3413,7 @@ DependenceInfo::depends(Instruction *Src, Instruction *Dst,
   if (Src == Dst)
     PossiblyLoopIndependent = false;
 
-  if ((!Src->mayReadFromMemory() && !Src->mayWriteToMemory()) ||
-      (!Dst->mayReadFromMemory() && !Dst->mayWriteToMemory()))
+  if (!(Src->mayReadOrWriteMemory() && Dst->mayReadOrWriteMemory()))
     // if both instructions don't reference memory, there's no dependence
     return nullptr;
 
@@ -3786,8 +3785,6 @@ DependenceInfo::depends(Instruction *Src, Instruction *Dst,
   return std::make_unique<FullDependence>(std::move(Result));
 }
 
-
-
 //===----------------------------------------------------------------------===//
 // getSplitIteration -
 // Rather than spend rarely-used space recording the splitting iteration

llvm/test/Analysis/DependenceAnalysis/Dump.ll

@@ -0,0 +1,50 @@
+; RUN: opt < %s -disable-output "-passes=print<da>" -aa-pipeline=basic-aa 2>&1 \
+; RUN: | FileCheck %s
+
+;; Test to make sure the dump shows the src and dst
+;; instructions (including call instructions).
+;;
+;; void bar(float * restrict A);
+;; void foo(float * restrict A, int n) {
+;;   for (int i = 0; i < n; i++) {
+;;     A[i] = i;
+;;     bar(A);
+;;   }
+;; }
+
+; CHECK-LABEL: foo
+
+; CHECK: Src:  store float %conv, float* %arrayidx, align 4 --> Dst:  store float %conv, float* %arrayidx, align 4
+; CHECK-NEXT:   da analyze - none!
+; CHECK-NEXT: Src:  store float %conv, float* %arrayidx, align 4 --> Dst:  call void @bar(float* %A)
+; CHECK-NEXT:   da analyze - confused!
+; CHECK-NEXT: Src:  call void @bar(float* %A) --> Dst:  call void @bar(float* %A)
+; CHECK-NEXT:   da analyze - confused!
+
+define void @foo(float* noalias %A, i32 signext %n) {
+entry:
+  %cmp1 = icmp slt i32 0, %n
+  br i1 %cmp1, label %for.body.lr.ph, label %for.end
+
+for.body.lr.ph:                                   ; preds = %entry
+  br label %for.body
+
+for.body:                                         ; preds = %for.body.lr.ph, %for.body
+  %i.02 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.body ]
+  %conv = sitofp i32 %i.02 to float
+  %idxprom = zext i32 %i.02 to i64
+  %arrayidx = getelementptr inbounds float, float* %A, i64 %idxprom
+  store float %conv, float* %arrayidx, align 4
+  call void @bar(float* %A) #3
+  %inc = add nuw nsw i32 %i.02, 1
+  %cmp = icmp slt i32 %inc, %n
+  br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge
+
+for.cond.for.end_crit_edge:                       ; preds = %for.body
+  br label %for.end
+
+for.end:                                          ; preds = %for.cond.for.end_crit_edge, %entry
+  ret void
+}
+
+declare void @bar(float*)