[llvm] b341c44 - [SimpleLoopUnswitch] Check if freeze is needed for partial unswitching.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2022-04-22T21:24:55+01:00
New Revision: b341c440102d1182953f7a23be2c457d1fda8b6d

URL: https://github.com/llvm/llvm-project/commit/b341c440102d1182953f7a23be2c457d1fda8b6d
DIFF: https://github.com/llvm/llvm-project/commit/b341c440102d1182953f7a23be2c457d1fda8b6d.diff

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

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.

Reviewed By: aeubanks, efriedma

Differential Revision: https://reviews.llvm.org/D124259

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
index cf19357f87ff8..7a29dbdc8be63 100644
--- a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
@@ -2313,9 +2313,13 @@ static void unswitchNontrivialInvariants(
     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) {

diff  --git a/llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-freeze.ll b/llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-freeze.ll
index 8ccc9d429e635..7b8cf5fd85778 100644
--- a/llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-freeze.ll
+++ b/llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch-freeze.ll
@@ -2333,8 +2333,7 @@ define i32 @test_partial_unswitch_all_conds_guaranteed_non_poison(i1 noundef %c.
 ; 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: