[GuardUtils] Revert llvm::isWidenableBranch change (#66411)

In the d6e7c16 was introduced util to
to extract widenable conditions from branch. That util was applied in
the llvm::isWidenableBranch to check if branch is widenable. So we
consider branch is widenable if it has widenable condition anywhere in
the condition tree. But that will be true when we finish GuardWidening
reworking from branch widening to widenable conditions widening.
For now we still need to check that widenable branch is in the form of:
`br(widenable_condition & (...))`,
because that form is assumed by LoopPredication and GuardWidening
algorithms.

Fixes: #66418

Co-authored-by: Aleksander Popov <apopov@azul.com>

llvm/lib/Analysis/GuardUtils.cpp

@@ -24,7 +24,10 @@ bool llvm::isWidenableCondition(const Value *V) {
 }
 
 bool llvm::isWidenableBranch(const User *U) {
-  return extractWidenableCondition(U) != nullptr;
+  Value *Condition, *WidenableCondition;
+  BasicBlock *GuardedBB, *DeoptBB;
+  return parseWidenableBranch(U, Condition, WidenableCondition, GuardedBB,
+                              DeoptBB);
 }
 
 bool llvm::isGuardAsWidenableBranch(const User *U) {

llvm/test/Transforms/LoopPredication/basic_widenable_branch_guards.ll

@@ -2144,6 +2144,56 @@ exit:                                             ; preds = %guarded, %entry
   ret i32 %result
 }
 
+; TODO: Support widenable branch in the form of br((wc and cond0) and cond1)
+; At present LoopPredication assumes the form of br(wc && (...)) only.
+define i32 @wc_deep_in_expression_tree(i1 %cond0, i1 %cond1, i32 %limit) {
+; CHECK-LABEL: @wc_deep_in_expression_tree(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[WC:%.*]] = call i1 @llvm.experimental.widenable.condition()
+; CHECK-NEXT:    [[AND0:%.*]] = and i1 [[WC]], [[COND0:%.*]]
+; CHECK-NEXT:    [[AND1:%.*]] = and i1 [[AND0]], [[COND1:%.*]]
+; CHECK-NEXT:    br i1 [[AND1]], label [[LOOP_PREHEADER:%.*]], label [[DEOPT:%.*]]
+; CHECK:       loop.preheader:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[IV_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    [[GUARD_COND:%.*]] = icmp sgt i32 [[IV]], 100
+; CHECK-NEXT:    br i1 [[GUARD_COND]], label [[DEOPT_LOOPEXIT:%.*]], label [[GUARDED]]
+; CHECK:       guarded:
+; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 1
+; CHECK-NEXT:    [[EXIT_COND:%.*]] = icmp ult i32 [[IV]], [[LIMIT:%.*]]
+; CHECK-NEXT:    br i1 [[EXIT_COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       deopt.loopexit:
+; CHECK-NEXT:    br label [[DEOPT]]
+; CHECK:       deopt:
+; CHECK-NEXT:    [[DEOPTCALL:%.*]] = call i32 (...) @llvm.experimental.deoptimize.i32(i32 9) [ "deopt"() ]
+; CHECK-NEXT:    ret i32 [[DEOPTCALL]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  %wc = call i1 @llvm.experimental.widenable.condition()
+  %and0 = and i1 %wc, %cond0
+  %and1 = and i1 %and0, %cond1
+  br i1 %and1, label %loop, label %deopt
+
+loop:
+  %iv = phi i32 [ %iv.next, %guarded ], [ 0, %entry ]
+  %guard.cond = icmp sgt i32 %iv, 100
+  br i1 %guard.cond, label %deopt, label %guarded
+
+guarded:
+  %iv.next = add i32 %iv, 1
+  %exit.cond = icmp ult i32 %iv, %limit
+  br i1 %exit.cond, label %loop, label %exit
+
+deopt:
+  %deoptcall = call i32 (...) @llvm.experimental.deoptimize.i32(i32 9) [ "deopt"() ]
+  ret i32 %deoptcall
+exit:
+  ret i32 0
+}
+
 declare i32 @llvm.experimental.deoptimize.i32(...)
 
 ; Function Attrs: inaccessiblememonly nounwind