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

[Aleksandr Popov via llvm-commits]

https://github.com/aleks-tmb updated https://github.com/llvm/llvm-project/pull/66411

>From 4f499699fce5009a4c826ef91dafce2054350ccb Mon Sep 17 00:00:00 2001
From: Aleksander Popov <apopov at azul.com>
Date: Thu, 14 Sep 2023 20:19:29 +0200
Subject: [PATCH] [GuardUtils] Revert llvm::isWidenableBranch change

In the d6e7c162e1df3736d8e2b3610a831b7cfa5be99b 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: https://github.com/llvm/llvm-project/issues/66418
---
 llvm/lib/Analysis/GuardUtils.cpp              |  5 +++-
 .../basic_widenable_branch_guards.ll          | 26 +++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Analysis/GuardUtils.cpp b/llvm/lib/Analysis/GuardUtils.cpp
index 83734b7eac0c823..b872286fb939618 100644
--- a/llvm/lib/Analysis/GuardUtils.cpp
+++ b/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) {
diff --git a/llvm/test/Transforms/LoopPredication/basic_widenable_branch_guards.ll b/llvm/test/Transforms/LoopPredication/basic_widenable_branch_guards.ll
index cad4fcec5c81abb..4d60914ebe2c473 100644
--- a/llvm/test/Transforms/LoopPredication/basic_widenable_branch_guards.ll
+++ b/llvm/test/Transforms/LoopPredication/basic_widenable_branch_guards.ll
@@ -2144,6 +2144,32 @@ 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) {
+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