[SimpleLoopUnswitch] Add freeze if branch execs for partial unswitching.

We cannot skip the freezing the condition if the unswitched branch
executes, if the condition is a chain of ANDs/ORs. For example, if if we
have an AND %c1, %c2 with  %c1 == undef and %c2 == 0, there would be no
branch on undef in the original code, but a branch on undef if we
unswitch %c1.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D124603

Author: fhahn

llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp

@@ -2321,9 +2321,9 @@ static void unswitchNontrivialInvariants(
       buildPartialInvariantUnswitchConditionalBranch(
           *SplitBB, Invariants, Direction, *ClonedPH, *LoopPH, L, MSSAU);
     else {
-      buildPartialUnswitchConditionalBranch(*SplitBB, Invariants, Direction,
-                                            *ClonedPH, *LoopPH, InsertFreeze,
-                                            BI, &AC, DT);
+      buildPartialUnswitchConditionalBranch(
+          *SplitBB, Invariants, Direction, *ClonedPH, *LoopPH,
+          FreezeLoopUnswitchCond, BI, &AC, DT);
     }
     DTUpdates.push_back({DominatorTree::Insert, SplitBB, ClonedPH});
 

llvm/test/Transforms/SimpleLoopUnswitch/nontrivial-unswitch.ll

@@ -2717,7 +2717,8 @@ define i32 @test25(i1* %ptr, i1 %cond) {
 entry:
   br label %loop_begin
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    br i1 %cond, label %entry.split.us, label %entry.split
+; CHECK-NEXT:    [[FROZEN:%.+]] = freeze i1 %cond
+; CHECK-NEXT:    br i1 [[FROZEN]], label %entry.split.us, label %entry.split
 
 loop_begin:
   %v1 = load i1, i1* %ptr
@@ -2790,7 +2791,9 @@ define i32 @test26(i1* %ptr1, i1* %ptr2, i1* %ptr3, i1 %cond1, i1 %cond2, i1 %co
 entry:
   br label %loop_begin
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    %[[INV_AND:.*]] = and i1 %cond3, %cond1
+; CHECK-NEXT:    [[C3_FR:%.+]] = freeze i1 %cond3
+; CHECK-NEXT:    [[C1_FR:%.+]] = freeze i1 %cond1
+; CHECK-NEXT:    %[[INV_AND:.*]] = and i1 [[C3_FR]], [[C1_FR]]
 ; CHECK-NEXT:    br i1 %[[INV_AND]], label %entry.split, label %entry.split.us
 
 loop_begin:
@@ -2871,7 +2874,9 @@ define i32 @test27(i1* %ptr1, i1* %ptr2, i1* %ptr3, i1 %cond1, i1 %cond2, i1 %co
 entry:
   br label %loop_begin
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    %[[INV_OR:.*]] = or i1 %cond3, %cond1
+; CHECK-NEXT:    [[C3_FR:%.+]] = freeze i1 %cond3
+; CHECK-NEXT:    [[C1_FR:%.+]] = freeze i1 %cond1
+; CHECK-NEXT:    %[[INV_OR:.*]] = or i1 [[C3_FR]], [[C1_FR]]
 ; CHECK-NEXT:    br i1 %[[INV_OR]], label %entry.split.us, label %entry.split
 
 loop_begin:
@@ -4231,7 +4236,9 @@ define i32 @test32(i1* %ptr1, i1* %ptr2, i1* %ptr3, i1 %cond1, i1 %cond2) {
 entry:
   br label %loop_begin
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    %[[INV_AND:.*]] = and i1 %cond2, %cond1
+; CHECK-NEXT:    [[C2_FR:%.+]] = freeze i1 %cond2
+; CHECK-NEXT:    [[C1_FR:%.+]] = freeze i1 %cond1
+; CHECK-NEXT:    %[[INV_AND:.*]] = and i1 [[C2_FR]], [[C1_FR]]
 ; CHECK-NEXT:    br i1 %[[INV_AND]], label %entry.split, label %entry.split.us
 
 loop_begin:
@@ -4309,7 +4316,9 @@ define i32 @test33(i1* %ptr1, i1* %ptr2, i1* %ptr3, i1 %cond1, i1 %cond2) {
 entry:
   br label %loop_begin
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    %[[INV_OR:.*]] = or i1 %cond2, %cond1
+; CHECK-NEXT:    [[C2_FR:%.+]] = freeze i1 %cond2
+; CHECK-NEXT:    [[C1_FR:%.+]] = freeze i1 %cond1
+; CHECK-NEXT:    %[[INV_OR:.*]] = or i1 [[C2_FR]], [[C1_FR]]
 ; CHECK-NEXT:    br i1 %[[INV_OR]], label %entry.split.us, label %entry.split
 
 loop_begin: