[llvm] 884e9a8 - [SimplifyCFG] Replace condition value when threading

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-04-29T09:50:27+02:00
New Revision: 884e9a877b378f5bf03f3c85a25b7a139ef6c8d8

URL: https://github.com/llvm/llvm-project/commit/884e9a877b378f5bf03f3c85a25b7a139ef6c8d8
DIFF: https://github.com/llvm/llvm-project/commit/884e9a877b378f5bf03f3c85a25b7a139ef6c8d8.diff

LOG: [SimplifyCFG] Replace condition value when threading

Replace the condition value with the known constant value on the
threaded edge. This happens implicitly with phi threading because
we replace with the incoming value, but not for non-phi threading.

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp
    llvm/test/Transforms/SimplifyCFG/jump-threading.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index cd47a1e7e456a..e86d253b9b9f0 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -3084,6 +3084,7 @@ FoldCondBranchOnValueKnownInPredecessorImpl(BranchInst *BI, DomTreeUpdater *DTU,
     // cloned instructions outside of EdgeBB.
     BasicBlock::iterator InsertPt = EdgeBB->begin();
     DenseMap<Value *, Value *> TranslateMap; // Track translated values.
+    TranslateMap[Cond] = Pair.second;
     for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) {
       if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
         TranslateMap[PN] = PN->getIncomingValueForBlock(PredBB);

diff  --git a/llvm/test/Transforms/SimplifyCFG/jump-threading.ll b/llvm/test/Transforms/SimplifyCFG/jump-threading.ll
index c401651c1df0c..59195660a3922 100644
--- a/llvm/test/Transforms/SimplifyCFG/jump-threading.ll
+++ b/llvm/test/Transforms/SimplifyCFG/jump-threading.ll
@@ -183,12 +183,12 @@ define void @test_same_cond_extra_use(i1 %c) {
 ; CHECK-NEXT:    br i1 [[C:%.*]], label [[IF:%.*]], label [[ELSE:%.*]]
 ; CHECK:       if:
 ; CHECK-NEXT:    call void @foo()
-; CHECK-NEXT:    call void @use.i1(i1 [[C]])
+; CHECK-NEXT:    call void @use.i1(i1 true)
 ; CHECK-NEXT:    call void @foo()
 ; CHECK-NEXT:    br label [[JOIN2:%.*]]
 ; CHECK:       else:
 ; CHECK-NEXT:    call void @bar()
-; CHECK-NEXT:    call void @use.i1(i1 [[C]])
+; CHECK-NEXT:    call void @use.i1(i1 false)
 ; CHECK-NEXT:    call void @bar()
 ; CHECK-NEXT:    br label [[JOIN2]]
 ; CHECK:       join2: