[PATCH] D85188: [JumpThreading] Remove cast's constraint

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune created this revision.
aqjune added reviewers: efriedma, lebedev.ri, nikic.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.
aqjune requested review of this revision.

As discussed in D84949 <https://reviews.llvm.org/D84949>, this removes the constraint to cast since it does not
cause compile time degradation.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D85188

Files:
  llvm/lib/Transforms/Scalar/JumpThreading.cpp
  llvm/test/Transforms/JumpThreading/threadable-edge-cast.ll


Index: llvm/test/Transforms/JumpThreading/threadable-edge-cast.ll
===================================================================
--- llvm/test/Transforms/JumpThreading/threadable-edge-cast.ll
+++ llvm/test/Transforms/JumpThreading/threadable-edge-cast.ll
@@ -11,20 +11,14 @@
 ; CHECK-NEXT:    br i1 [[COND0:%.*]], label [[T1:%.*]], label [[F1:%.*]]
 ; CHECK:       T1:
 ; CHECK-NEXT:    [[V1:%.*]] = call i32 @f1()
-; CHECK-NEXT:    br label [[MERGE:%.*]]
+; CHECK-NEXT:    br label [[F2:%.*]]
 ; CHECK:       F1:
 ; CHECK-NEXT:    [[V2:%.*]] = call i32 @f2()
-; CHECK-NEXT:    br label [[MERGE]]
-; CHECK:       Merge:
+; CHECK-NEXT:    br label [[F2]]
+; CHECK:       F2:
 ; CHECK-NEXT:    [[A:%.*]] = phi i32 [ 10, [[T1]] ], [ 0, [[F1]] ]
 ; CHECK-NEXT:    [[B:%.*]] = phi i32 [ [[V1]], [[T1]] ], [ [[V2]], [[F1]] ]
 ; CHECK-NEXT:    [[AND:%.*]] = and i32 [[A]], 1
-; CHECK-NEXT:    [[COND:%.*]] = trunc i32 [[AND]] to i1
-; CHECK-NEXT:    br i1 [[COND]], label [[T2:%.*]], label [[F2:%.*]]
-; CHECK:       T2:
-; CHECK-NEXT:    call void @f3()
-; CHECK-NEXT:    ret i32 [[B]]
-; CHECK:       F2:
 ; CHECK-NEXT:    ret i32 [[B]]
 ;
   br i1 %cond0, label %T1, label %F1
@@ -57,21 +51,15 @@
 ; CHECK-NEXT:    br i1 [[COND0:%.*]], label [[T1:%.*]], label [[F1:%.*]]
 ; CHECK:       T1:
 ; CHECK-NEXT:    [[V1:%.*]] = call i32 @f1()
-; CHECK-NEXT:    br label [[MERGE:%.*]]
+; CHECK-NEXT:    br label [[F2:%.*]]
 ; CHECK:       F1:
 ; CHECK-NEXT:    [[V2:%.*]] = call i32 @f2()
-; CHECK-NEXT:    br label [[MERGE]]
-; CHECK:       Merge:
+; CHECK-NEXT:    br label [[F2]]
+; CHECK:       F2:
 ; CHECK-NEXT:    [[A:%.*]] = phi i1 [ true, [[T1]] ], [ false, [[F1]] ]
 ; CHECK-NEXT:    [[B:%.*]] = phi i32 [ [[V1]], [[T1]] ], [ [[V2]], [[F1]] ]
 ; CHECK-NEXT:    [[A2:%.*]] = xor i1 [[A]], true
 ; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[A2]], i32 10, i32 0
-; CHECK-NEXT:    [[COND:%.*]] = trunc i32 [[SEL]] to i1
-; CHECK-NEXT:    br i1 [[COND]], label [[T2:%.*]], label [[F2:%.*]]
-; CHECK:       T2:
-; CHECK-NEXT:    call void @f3()
-; CHECK-NEXT:    ret i32 [[B]]
-; CHECK:       F2:
 ; CHECK-NEXT:    ret i32 [[B]]
 ;
   br i1 %cond0, label %T1, label %F1
Index: llvm/lib/Transforms/Scalar/JumpThreading.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -674,13 +674,9 @@
     return !Result.empty();
   }
 
-  // Handle Cast instructions.  Only see through Cast when the source operand is
-  // PHI, Cmp, or Freeze to save the compilation time.
+  // Handle Cast instructions.
   if (CastInst *CI = dyn_cast<CastInst>(I)) {
     Value *Source = CI->getOperand(0);
-    if (!isa<PHINode>(Source) && !isa<CmpInst>(Source) &&
-        !isa<FreezeInst>(Source))
-      return false;
     ComputeValueKnownInPredecessorsImpl(Source, BB, Result, Preference,
                                         RecursionSet, CxtI);
     if (Result.empty())


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