PGO: preserve branch-weight metadata when merging two switches where

the default target of the first switch is not the basic block the second switch
is in (PredDefault != BB).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163916 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 142f157c3c84d7a69c648effb5ed43e04ef5c2f9..2591dbf726227b5562d83727ab299f619eed6c0b 100644 (file)
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -898,18 +898,21 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
           Weights[0] *= SuccWeights[0];
         }
       } else {
-        // FIXME: preserve branch weight metadata, similarly to the 'then'
-        // above. For now, drop it.
-        PredHasWeights = false;
-        SuccHasWeights = false;
-
         // If this is not the default destination from PSI, only the edges
         // in SI that occur in PSI with a destination of BB will be
         // activated.
         std::set<ConstantInt*, ConstantIntOrdering> PTIHandled;
+        std::map<ConstantInt*, uint64_t> WeightsForHandled;
         for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
           if (PredCases[i].Dest == BB) {
             PTIHandled.insert(PredCases[i].Value);
+
+            if (PredHasWeights || SuccHasWeights) {
+              WeightsForHandled[PredCases[i].Value] = Weights[i+1];
+              std::swap(Weights[i+1], Weights.back());
+              Weights.pop_back();
+            }
+
             std::swap(PredCases[i], PredCases.back());
             PredCases.pop_back();
             --i; --e;
@@ -920,6 +923,8 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
         for (unsigned i = 0, e = BBCases.size(); i != e; ++i)
           if (PTIHandled.count(BBCases[i].Value)) {
             // If this is one we are capable of getting...
+            if (PredHasWeights || SuccHasWeights)
+              Weights.push_back(WeightsForHandled[BBCases[i].Value]);
             PredCases.push_back(BBCases[i]);
             NewSuccessors.push_back(BBCases[i].Dest);
             PTIHandled.erase(BBCases[i].Value);// This constant is taken care of
@@ -930,6 +935,8 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
         for (std::set<ConstantInt*, ConstantIntOrdering>::iterator I =
                                     PTIHandled.begin(),
                E = PTIHandled.end(); I != E; ++I) {
+          if (PredHasWeights || SuccHasWeights) 
+            Weights.push_back(WeightsForHandled[*I]); 
           PredCases.push_back(ValueEqualityComparisonCase(*I, BBDefault));
           NewSuccessors.push_back(BBDefault);
         }

diff --git a/test/Transforms/SimplifyCFG/preserve-branchweights-switch-create.ll b/test/Transforms/SimplifyCFG/preserve-branchweights-switch-create.ll
index 75f5f06daa7d615b609ef636be2361a1332cbd52..941f5ad9d5b64f2b9c5861ce380ccd2c913f3eaa 100644 (file)
--- a/test/Transforms/SimplifyCFG/preserve-branchweights-switch-create.ll
+++ b/test/Transforms/SimplifyCFG/preserve-branchweights-switch-create.ll
@@ -84,9 +84,57 @@ sw.epilog:
   ret void
 }
 
+;; test3 - Merge two switches where PredDefault != BB.
+define void @test3(i32 %M, i32 %N) nounwind uwtable {
+entry:
+  %cmp = icmp sgt i32 %M, 2
+  br i1 %cmp, label %sw1, label %sw2
+
+sw1:
+  switch i32 %N, label %sw.bb [
+    i32 2, label %sw2
+    i32 3, label %sw2
+    i32 1, label %sw.bb1
+  ], !prof !4
+; CHECK: test3
+; CHECK: switch i32 %N, label %sw.bb
+; CHECK: i32 1, label %sw.bb1
+; CHECK: i32 3, label %sw.bb4
+; CHECK: i32 2, label %sw.epilog
+; CHECK: ], !prof !3
+
+sw.bb:
+  call void @func2(i32 %N) nounwind
+  br label %sw.epilog
+
+sw.bb1:
+  call void @func4(i32 %N) nounwind
+  br label %sw.epilog
+
+sw2:
+  switch i32 %N, label %sw.epilog [
+    i32 3, label %sw.bb4
+    i32 4, label %sw.bb5
+  ], !prof !5
+
+sw.bb4:
+  call void @func6(i32 %N) nounwind
+  br label %sw.epilog
+
+sw.bb5:
+  call void @func8(i32 %N) nounwind
+  br label %sw.epilog
+
+sw.epilog:
+  ret void
+}
+
 !0 = metadata !{metadata !"branch_weights", i32 64, i32 4}
 !1 = metadata !{metadata !"branch_weights", i32 4, i32 64}
 ; CHECK: !0 = metadata !{metadata !"branch_weights", i32 256, i32 4352, i32 16}
 !2 = metadata !{metadata !"branch_weights", i32 4, i32 4, i32 8}
 !3 = metadata !{metadata !"branch_weights", i32 8, i32 8, i32 4}
 ; CHECK: !1 = metadata !{metadata !"branch_weights", i32 32, i32 48, i32 96, i32 16}
+!4 = metadata !{metadata !"branch_weights", i32 7, i32 6, i32 4, i32 3}
+!5 = metadata !{metadata !"branch_weights", i32 17, i32 13, i32 9}
+; CHECK: !3 = metadata !{metadata !"branch_weights", i32 7, i32 3, i32 4, i32 6}