[PATCH] D81822: [DA] propagate loop live-out values that get used in a branch

[Sameer Sahasrabuddhe via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rGd3963b3a5f4f: [DA] propagate loop live-out values that get used in a branch (authored by sameerds).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D81822/new/

https://reviews.llvm.org/D81822

Files:
  llvm/lib/Analysis/DivergenceAnalysis.cpp
  llvm/test/Analysis/DivergenceAnalysis/AMDGPU/propagate-loop-live-out.ll


Index: llvm/test/Analysis/DivergenceAnalysis/AMDGPU/propagate-loop-live-out.ll
===================================================================
--- /dev/null
+++ llvm/test/Analysis/DivergenceAnalysis/AMDGPU/propagate-loop-live-out.ll
@@ -0,0 +1,48 @@
+; RUN: opt -mtriple amdgcn-unknown-amdhsa -analyze -divergence -use-gpu-divergence-analysis %s | FileCheck %s
+
+; CHECK: bb6:
+; CHECK: DIVERGENT:       %.126.i355.i = phi i1 [ false, %bb5 ], [ true, %bb4 ]
+; CHECK: DIVERGENT:       br i1 %.126.i355.i, label %bb7, label %bb8
+
+; Function Attrs: nounwind readnone speculatable
+declare i32 @llvm.amdgcn.workitem.id.x() #0
+
+define protected amdgpu_kernel void @_Z23krnl_GPUITSFitterKerneli() {
+bb0:
+  %i4 = call i32 @llvm.amdgcn.workitem.id.x()
+  %i5 = icmp eq i32 %i4, -1
+  br label %bb1
+
+bb1:                                              ; preds = %bb3, %bb0
+  %lsr.iv = phi i32 [ %i1, %bb3 ], [ 7, %bb0 ]
+  br i1 %i5, label %bb2, label %bb3
+
+bb2:                                              ; preds = %bb1
+  %lsr.iv.next = add nsw i32 %lsr.iv, -1
+  %i14 = icmp eq i32 %lsr.iv.next, 0
+  br label %bb3
+
+bb3:                                              ; preds = %bb2, %bb1
+  %i1 = phi i32 [ %lsr.iv.next, %bb2 ], [ 0, %bb1 ]
+  %i2 = phi i1 [ false, %bb2 ], [ true, %bb1 ]
+  %i3 = phi i1 [ %i14, %bb2 ], [ true, %bb1 ]
+  br i1 %i3, label %bb4, label %bb1
+
+bb4:                                              ; preds = %bb3
+  br i1 %i2, label %bb5, label %bb6
+
+bb5:                                              ; preds = %bb4
+  br label %bb6
+
+bb6:                                              ; preds = %bb5, %bb4
+  %.126.i355.i = phi i1 [ false, %bb5 ], [ true, %bb4 ]
+  br i1 %.126.i355.i, label %bb7, label %bb8
+
+bb7:                                              ; preds = %bb6
+  br label %bb8
+
+bb8:                                              ; preds = %bb7, %bb6
+  ret void
+}
+
+attributes #0 = { nounwind readnone speculatable }
Index: llvm/lib/Analysis/DivergenceAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/DivergenceAnalysis.cpp
+++ llvm/lib/Analysis/DivergenceAnalysis.cpp
@@ -184,6 +184,17 @@
   return (!RegionLoop && BB.getParent() == &F) || RegionLoop->contains(&BB);
 }
 
+static bool usesLiveOut(const Instruction &I, const Loop *DivLoop) {
+  for (auto &Op : I.operands()) {
+    auto *OpInst = dyn_cast<Instruction>(&Op);
+    if (!OpInst)
+      continue;
+    if (DivLoop->contains(OpInst->getParent()))
+      return true;
+  }
+  return false;
+}
+
 // marks all users of loop-carried values of the loop headed by LoopHeader as
 // divergent
 void DivergenceAnalysis::taintLoopLiveOuts(const BasicBlock &LoopHeader) {
@@ -227,16 +238,14 @@
         continue;
       if (isDivergent(I))
         continue;
+      if (!usesLiveOut(I, DivLoop))
+        continue;
 
-      for (auto &Op : I.operands()) {
-        auto *OpInst = dyn_cast<Instruction>(&Op);
-        if (!OpInst)
-          continue;
-        if (DivLoop->contains(OpInst->getParent())) {
-          markDivergent(I);
-          pushUsers(I);
-          break;
-        }
+      markDivergent(I);
+      if (I.isTerminator()) {
+        propagateBranchDivergence(I);
+      } else {
+        pushUsers(I);
       }
     }
 


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