[llvm] cfc9298 - [CHR] Fix up phi nodes with unreachable predecessors (PR64594)

Nikita Popov via llvm-commits llvm-commits at lists.llvm.org
Fri Aug 11 00:38:09 PDT 2023


Author: Nikita Popov
Date: 2023-08-11T09:38:01+02:00
New Revision: cfc9298dc588c626a52193260da28a630e103916

URL: https://github.com/llvm/llvm-project/commit/cfc9298dc588c626a52193260da28a630e103916
DIFF: https://github.com/llvm/llvm-project/commit/cfc9298dc588c626a52193260da28a630e103916.diff

LOG: [CHR] Fix up phi nodes with unreachable predecessors (PR64594)

If a block in the CHR region has an unreachable predecessor, then
there will be no edge from that predecessor to the newly cloned
block. However, a phi node entry for it will be left behind. Make
sure that these incoming blocks get dropped as well.

Fixes https://github.com/llvm/llvm-project/issues/64594.

Differential Revision: https://reviews.llvm.org/D157621

Added: 
    llvm/test/Transforms/PGOProfile/chr-dead-pred.ll

Modified: 
    llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp b/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp
index 3e3be536defc5d..478e45b95cbdd5 100644
--- a/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp
+++ b/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp
@@ -1777,6 +1777,21 @@ void CHR::cloneScopeBlocks(CHRScope *Scope,
       BasicBlock *NewBB = CloneBasicBlock(BB, VMap, ".nonchr", &F);
       NewBlocks.push_back(NewBB);
       VMap[BB] = NewBB;
+
+      // Unreachable predecessors will not be cloned and will not have an edge
+      // to the cloned block. As such, also remove them from any phi nodes.
+      // To avoid iterator invalidation, first collect the dead predecessors
+      // from the first phi node, and then perform the actual removal.
+      SmallVector<BasicBlock *> DeadPreds;
+      for (PHINode &PN : NewBB->phis()) {
+        for (BasicBlock *Pred : PN.blocks())
+          if (!DT.isReachableFromEntry(Pred))
+            DeadPreds.push_back(Pred);
+        break;
+      }
+      for (PHINode &PN : make_early_inc_range(NewBB->phis()))
+        for (BasicBlock *Pred : DeadPreds)
+          PN.removeIncomingValue(Pred);
     }
 
   // Place the cloned blocks right after the original blocks (right before the

diff  --git a/llvm/test/Transforms/PGOProfile/chr-dead-pred.ll b/llvm/test/Transforms/PGOProfile/chr-dead-pred.ll
new file mode 100644
index 00000000000000..bdbf0640035d41
--- /dev/null
+++ b/llvm/test/Transforms/PGOProfile/chr-dead-pred.ll
@@ -0,0 +1,106 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -S -passes='require<profile-summary>,chr' < %s | FileCheck %s
+
+define void @test(i1 %c, i1 %c2) !prof !29 {
+; CHECK-LABEL: define void @test
+; CHECK-SAME: (i1 [[C:%.*]], i1 [[C2:%.*]]) !prof [[PROF29:![0-9]+]] {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = xor i1 true, [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = freeze i1 [[TMP0]]
+; CHECK-NEXT:    [[TMP2:%.*]] = select i1 true, i1 [[TMP1]], i1 false
+; CHECK-NEXT:    [[TMP3:%.*]] = xor i1 true, [[C2]]
+; CHECK-NEXT:    [[TMP4:%.*]] = freeze i1 [[TMP3]]
+; CHECK-NEXT:    [[TMP5:%.*]] = select i1 [[TMP2]], i1 [[TMP4]], i1 false
+; CHECK-NEXT:    br i1 [[TMP5]], label [[ENTRY_SPLIT:%.*]], label [[ENTRY_SPLIT_NONCHR:%.*]], !prof [[PROF30:![0-9]+]]
+; CHECK:       entry.split:
+; CHECK-NEXT:    switch i8 0, label [[BB1:%.*]] [
+; CHECK-NEXT:    i8 1, label [[BB2:%.*]]
+; CHECK-NEXT:    i8 2, label [[BB3:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 false, i32 0, i32 1, !prof [[PROF31:![0-9]+]]
+; CHECK-NEXT:    br label [[EXIT:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[SELECT3:%.*]] = select i1 false, i32 0, i32 1, !prof [[PROF32:![0-9]+]]
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       dead:
+; CHECK-NEXT:    br label [[BB3]]
+; CHECK:       bb3:
+; CHECK-NEXT:    [[PHI:%.*]] = phi i64 [ 0, [[DEAD:%.*]] ], [ 1, [[ENTRY_SPLIT]] ]
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       entry.split.nonchr:
+; CHECK-NEXT:    switch i8 0, label [[BB1_NONCHR:%.*]] [
+; CHECK-NEXT:    i8 1, label [[BB2_NONCHR:%.*]]
+; CHECK-NEXT:    i8 2, label [[BB3_NONCHR:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       bb1.nonchr:
+; CHECK-NEXT:    [[SELECT_NONCHR:%.*]] = select i1 [[C]], i32 0, i32 1, !prof [[PROF31]]
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       bb2.nonchr:
+; CHECK-NEXT:    [[SELECT3_NONCHR:%.*]] = select i1 [[C2]], i32 0, i32 1, !prof [[PROF32]]
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       bb3.nonchr:
+; CHECK-NEXT:    [[PHI_NONCHR:%.*]] = phi i64 [ 1, [[ENTRY_SPLIT_NONCHR]] ]
+; CHECK-NEXT:    br label [[EXIT]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+;
+entry:
+  switch i8 0, label %bb1 [
+  i8 1, label %bb2
+  i8 2, label %bb3
+  ]
+
+bb1:                                              ; preds = %entry
+  %select = select i1 %c, i32 0, i32 1, !prof !30
+  br label %exit
+
+bb2:                                              ; preds = %entry
+  %select3 = select i1 %c2, i32 0, i32 1, !prof !31
+  br label %exit
+
+dead:                                             ; No predecessors!
+  br label %bb3
+
+bb3:                                              ; preds = %dead, %entry
+  %phi = phi i64 [ 0, %dead ], [ 1, %entry ]
+  br label %exit
+
+exit:                                             ; preds = %bb3, %bb2, %bb1
+  ret void
+}
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"ProfileSummary", !1}
+!1 = !{!2, !3, !4, !5, !6, !7, !8, !9, !10, !11}
+!2 = !{!"ProfileFormat", !"InstrProf"}
+!3 = !{!"TotalCount", i64 597326977313}
+!4 = !{!"MaxCount", i64 12561793713}
+!5 = !{!"MaxInternalCount", i64 2509052618}
+!6 = !{!"MaxFunctionCount", i64 12561793713}
+!7 = !{!"NumCounts", i64 1694881}
+!8 = !{!"NumFunctions", i64 129214}
+!9 = !{!"IsPartialProfile", i64 0}
+!10 = !{!"PartialProfileRatio", double 0.000000e+00}
+!11 = !{!"DetailedSummary", !12}
+!12 = !{!13, !14, !15, !16, !17, !18, !19, !20, !21, !22, !23, !24, !25, !26, !27, !28}
+!13 = !{i32 10000, i64 12561793713, i32 1}
+!14 = !{i32 100000, i64 1733566697, i32 20}
+!15 = !{i32 200000, i64 820928443, i32 71}
+!16 = !{i32 300000, i64 404967336, i32 182}
+!17 = !{i32 400000, i64 233162193, i32 376}
+!18 = !{i32 500000, i64 120552435, i32 741}
+!19 = !{i32 600000, i64 69388652, i32 1402}
+!20 = !{i32 700000, i64 33926336, i32 2643}
+!21 = !{i32 800000, i64 15635940, i32 5288}
+!22 = !{i32 900000, i64 5547105, i32 11637}
+!23 = !{i32 950000, i64 2224405, i32 20074}
+!24 = !{i32 990000, i64 359838, i32 44778}
+!25 = !{i32 999000, i64 37485, i32 81744}
+!26 = !{i32 999900, i64 3465, i32 119656}
+!27 = !{i32 999990, i64 529, i32 155440}
+!28 = !{i32 999999, i64 70, i32 178344}
+!29 = !{!"function_entry_count", i64 33781183}
+!30 = !{!"branch_weights", i32 0, i32 9263770}
+!31 = !{!"branch_weights", i32 0, i32 634318}


        


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