[PATCH] D84598: [JumpThreading] Add a basic support for freeze instruction

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune updated this revision to Diff 280726.
aqjune added a comment.

Temporarily hide the negative test because its output was a bit strange


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D84598/new/

https://reviews.llvm.org/D84598

Files:
  llvm/lib/Transforms/Scalar/JumpThreading.cpp
  llvm/test/Transforms/JumpThreading/freeze.ll


Index: llvm/test/Transforms/JumpThreading/freeze.ll
===================================================================
--- llvm/test/Transforms/JumpThreading/freeze.ll
+++ llvm/test/Transforms/JumpThreading/freeze.ll
@@ -7,23 +7,14 @@
 
 define i32 @test1(i1 %cond) {
 ; CHECK-LABEL: @test1(
-; CHECK-NEXT:    br i1 [[COND:%.*]], label [[T1:%.*]], label [[F1:%.*]]
-; CHECK:       T1:
-; CHECK-NEXT:    [[V1:%.*]] = call i32 @f1()
-; CHECK-NEXT:    br label [[MERGE:%.*]]
-; CHECK:       F1:
-; CHECK-NEXT:    [[V2:%.*]] = call i32 @f2()
-; CHECK-NEXT:    br label [[MERGE]]
-; CHECK:       Merge:
-; CHECK-NEXT:    [[A:%.*]] = phi i1 [ true, [[T1]] ], [ false, [[F1]] ]
-; CHECK-NEXT:    [[B:%.*]] = phi i32 [ [[V1]], [[T1]] ], [ [[V2]], [[F1]] ]
-; CHECK-NEXT:    [[A_FR:%.*]] = freeze i1 [[A]]
-; CHECK-NEXT:    br i1 [[A_FR]], label [[T2:%.*]], label [[F2:%.*]]
+; CHECK-NEXT:    br i1 [[COND:%.*]], label [[T2:%.*]], label [[F2:%.*]]
 ; CHECK:       T2:
+; CHECK-NEXT:    [[V1:%.*]] = call i32 @f1()
 ; CHECK-NEXT:    call void @f3()
-; CHECK-NEXT:    ret i32 [[B]]
+; CHECK-NEXT:    ret i32 [[V1]]
 ; CHECK:       F2:
-; CHECK-NEXT:    ret i32 [[B]]
+; CHECK-NEXT:    [[V2:%.*]] = call i32 @f2()
+; CHECK-NEXT:    ret i32 [[V2]]
 ;
   br i1 %cond, label %T1, label %F1
 
@@ -51,23 +42,20 @@
 
 define i32 @test2(i1 %cond, i1 %cond2) {
 ; CHECK-LABEL: @test2(
-; CHECK-NEXT:    br i1 [[COND:%.*]], label [[T1:%.*]], label [[F1:%.*]]
-; CHECK:       T1:
+; CHECK-NEXT:    br i1 [[COND:%.*]], label [[MERGE_THREAD:%.*]], label [[MERGE:%.*]]
+; CHECK:       Merge.thread:
 ; CHECK-NEXT:    [[V1:%.*]] = call i32 @f1()
-; CHECK-NEXT:    br label [[MERGE:%.*]]
-; CHECK:       F1:
-; CHECK-NEXT:    [[V2:%.*]] = call i32 @f2()
-; CHECK-NEXT:    br label [[MERGE]]
+; CHECK-NEXT:    br label [[T2:%.*]]
 ; CHECK:       Merge:
-; CHECK-NEXT:    [[A:%.*]] = phi i1 [ true, [[T1]] ], [ [[COND2:%.*]], [[F1]] ]
-; CHECK-NEXT:    [[B:%.*]] = phi i32 [ [[V1]], [[T1]] ], [ [[V2]], [[F1]] ]
-; CHECK-NEXT:    [[A_FR:%.*]] = freeze i1 [[A]]
-; CHECK-NEXT:    br i1 [[A_FR]], label [[T2:%.*]], label [[F2:%.*]]
+; CHECK-NEXT:    [[V2:%.*]] = call i32 @f2()
+; CHECK-NEXT:    [[A_FR:%.*]] = freeze i1 [[COND2:%.*]]
+; CHECK-NEXT:    br i1 [[A_FR]], label [[T2]], label [[F2:%.*]]
 ; CHECK:       T2:
+; CHECK-NEXT:    [[B4:%.*]] = phi i32 [ [[V1]], [[MERGE_THREAD]] ], [ [[V2]], [[MERGE]] ]
 ; CHECK-NEXT:    call void @f3()
-; CHECK-NEXT:    ret i32 [[B]]
+; CHECK-NEXT:    ret i32 [[B4]]
 ; CHECK:       F2:
-; CHECK-NEXT:    ret i32 [[B]]
+; CHECK-NEXT:    ret i32 [[V2]]
 ;
   br i1 %cond, label %T1, label %F1
 
Index: llvm/lib/Transforms/Scalar/JumpThreading.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -692,6 +692,24 @@
     return true;
   }
 
+  // Handle Freeze instructions, in a manner similar to Cast.
+  if (FreezeInst *FI = dyn_cast<FreezeInst>(I)) {
+    Value *Source = FI->getOperand(0);
+    if (!isa<PHINode>(Source) && !isa<CmpInst>(Source))
+      return false;
+    ComputeValueKnownInPredecessorsImpl(Source, BB, Result, Preference,
+                                        RecursionSet, CxtI);
+
+    for (unsigned i = 0; i < Result.size(); ++i) {
+      if (!isGuaranteedNotToBeUndefOrPoison(Result[i].first)) {
+        Result.erase(Result.begin() + i);
+        i--;
+      }
+    }
+
+    return !Result.empty();
+  }
+
   // Handle some boolean conditions.
   if (I->getType()->getPrimitiveSizeInBits() == 1) {
     assert(Preference == WantInteger && "One-bit non-integer type?");


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