[GuardUtils] Revert llvm::isWidenableBranch change

[aleks-tmb]

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

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

@llvm/pr-subscribers-llvm-analysis

Changes

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 & (...)) -- Full diff: https://github.com//pull/66411.diff

2 Files Affected:

• (modified) llvm/lib/Analysis/GuardUtils.cpp (+4-1)
• (modified) llvm/test/Transforms/LoopPredication/basic_widenable_branch_guards.ll (+25)

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..d68279cc7d0b937 100644
--- a/llvm/test/Transforms/LoopPredication/basic_widenable_branch_guards.ll
+++ b/llvm/test/Transforms/LoopPredication/basic_widenable_branch_guards.ll
@@ -2144,6 +2144,31 @@ exit:                                             ; preds = %guarded, %entry
   ret i32 %result
 }
 
+; TODO: Support widenable branch in the form of br((wc and cond0) and cond1)
+define i32 @hoge(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

[annamthomas]

For now we still need to check that widenable branch is in the form of: br(widenable_condition & (...))

I think it will be clearer to state why we need to do this check either in the commit message or as a statement in the test added.

[aleks-tmb]

For now we still need to check that widenable branch is in the form of: br(widenable_condition & (...))

I think it will be clearer to state why we need to do this check either in the commit message or as a statement in the test added.

Done

[annamthomas]

Thanks. LGTM.