[PATCH] D124259: [SimpleLoopUnswitch] Check if freeze is needed for partial unswitching.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: asbirlea, nikic, aeubanks, aqjune, efriedma.
Herald added a subscriber: hiraditya.
Herald added a project: All.
fhahn requested review of this revision.
Herald added a project: LLVM.

We only need to insert a Freeze instruction if any of the conditions
may be poison. Similar checks are already done in the other places
SimpleLoopUnswitch creates Freeze instruction.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D124259

Files:
  llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
  llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-freeze.ll


Index: llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-freeze.ll
===================================================================
--- llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-freeze.ll
+++ llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-freeze.ll
@@ -2333,8 +2333,7 @@
 ; CHECK-LABEL: @test_partial_unswitch_all_conds_guaranteed_non_poison(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[TMP0:%.*]] = and i1 [[C_1:%.*]], [[C_2:%.*]]
-; CHECK-NEXT:    [[DOTFR:%.*]] = freeze i1 [[TMP0]]
-; CHECK-NEXT:    br i1 [[DOTFR]], label [[ENTRY_SPLIT:%.*]], label [[ENTRY_SPLIT_US:%.*]]
+; CHECK-NEXT:    br i1 [[TMP0]], label [[ENTRY_SPLIT:%.*]], label [[ENTRY_SPLIT_US:%.*]]
 ; CHECK:       entry.split.us:
 ; CHECK-NEXT:    br label [[LOOP_US:%.*]]
 ; CHECK:       loop.us:
Index: llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
+++ llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
@@ -2313,9 +2313,13 @@
     if (PartiallyInvariant)
       buildPartialInvariantUnswitchConditionalBranch(
           *SplitBB, Invariants, Direction, *ClonedPH, *LoopPH, L, MSSAU);
-    else
-      buildPartialUnswitchConditionalBranch(*SplitBB, Invariants, Direction,
-                                            *ClonedPH, *LoopPH, InsertFreeze);
+    else {
+      buildPartialUnswitchConditionalBranch(
+          *SplitBB, Invariants, Direction, *ClonedPH, *LoopPH,
+          InsertFreeze && any_of(Invariants, [&](Value *C) {
+            return !isGuaranteedNotToBeUndefOrPoison(C, &AC, BI, &DT);
+          }));
+    }
     DTUpdates.push_back({DominatorTree::Insert, SplitBB, ClonedPH});
 
     if (MSSAU) {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D124259.424465.patch
Type: text/x-patch
Size: 1761 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220422/af6ef610/attachment.bin>