[PATCH] D93410: [SimplifyCFG] Preserve !annotation in FoldBranchToCommonDest.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: thegameg, spatel, jdoerfert, RKSimon, lebedev.ri.
Herald added a subscriber: hiraditya.
fhahn requested review of this revision.
Herald added a project: LLVM.

When folding a branch to a common destination, preserve !annotation on
the created instruction, if the terminator of the BB that is going to be
removed has !annotation. This should ensure that !annotation is attached
to the instructions that 'replace' the original terminator.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D93410

Files:
  llvm/lib/Transforms/Utils/SimplifyCFG.cpp
  llvm/test/Transforms/SimplifyCFG/annotations.ll


Index: llvm/test/Transforms/SimplifyCFG/annotations.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/annotations.ll
+++ llvm/test/Transforms/SimplifyCFG/annotations.ll
@@ -6,8 +6,8 @@
 ; CHECK-LABEL: define {{.*}} @test_preserve_and({{.*}}
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp ult i8* [[A:%.*]], [[B:%.*]], !annotation !0
-; CHECK-NEXT:    [[C_2:%.*]] = icmp uge i8* [[C:%.*]], [[D:%.*]]
-; CHECK-NEXT:    [[OR_COND:%.*]] = and i1 [[C_1]], [[C_2]]
+; CHECK-NEXT:    [[C_2:%.*]] = icmp uge i8* [[C:%.*]], [[D:%.*]], !annotation !0
+; CHECK-NEXT:    [[OR_COND:%.*]] = and i1 [[C_1]], [[C_2]], !annotation !0
 ; CHECK-NEXT:    br i1 [[OR_COND]], label [[CONT1:%.*]], label [[TRAP:%.*]], !annotation !0
 ; CHECK:       trap: ; preds = %entry
 ; CHECK-NEXT:    call void @fn1()
@@ -39,8 +39,8 @@
 ; CHECK-LABEL: define {{.*}} @test_preserve_or({{.*}}
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp uge i8* [[A:%.*]], [[B:%.*]], !annotation !0
-; CHECK-NEXT:    [[C_2:%.*]] = icmp uge i8* [[C:%.*]], [[D:%.*]]
-; CHECK-NEXT:    [[OR_COND:%.*]] = or i1 [[C_1]], [[C_2]]
+; CHECK-NEXT:    [[C_2:%.*]] = icmp uge i8* [[C:%.*]], [[D:%.*]], !annotation !0
+; CHECK-NEXT:    [[OR_COND:%.*]] = or i1 [[C_1]], [[C_2]], !annotation !0
 ; CHECK-NEXT:    br i1 [[OR_COND]], label [[TRAP:%.*]], label [[CONT1:%.*]], !annotation !0
 ; CHECK:       trap: ; preds = %entry
 ; CHECK-NEXT:    call void @fn1()
@@ -73,9 +73,9 @@
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp ult i8* [[A:%.*]], [[B:%.*]], !annotation !0
 ; CHECK-NEXT:    [[C_2:%.*]] = xor i1 [[C_1]], true
-; CHECK-NEXT:    [[C_2_NOT:%.*]] = xor i1 [[C_2]], true
-; CHECK-NEXT:    [[C_3:%.*]] = icmp uge i8* [[C:%.*]], [[D:%.*]]
-; CHECK-NEXT:    [[OR_COND:%.*]] = or i1 [[C_2_NOT]], [[C_3]]
+; CHECK-NEXT:    [[C_2_NOT:%.*]] = xor i1 [[C_2]], true, !annotation !0
+; CHECK-NEXT:    [[C_3:%.*]] = icmp uge i8* [[C:%.*]], [[D:%.*]], !annotation !0
+; CHECK-NEXT:    [[OR_COND:%.*]] = or i1 [[C_2_NOT]], [[C_3]], !annotation !0
 ; CHECK-NEXT:    br i1 [[OR_COND]], label [[TRAP:%.*]], label [[CONT1:%.*]], !annotation !0
 ; CHECK:       trap: ; preds = %entry
 ; CHECK-NEXT:    call void @fn1()
@@ -111,7 +111,7 @@
 ; CHECK-NEXT:    [[C_1:%.*]] = icmp ult i8* [[A:%.*]], [[B:%.*]], !annotation !0
 ; CHECK-NEXT:    [[C_2:%.*]] = xor i1 [[C_1]], true
 ; CHECK-NEXT:    [[C_2_NOT:%.*]] = xor i1 [[C_2]], true
-; CHECK-NEXT:    [[C_3:%.*]] = icmp uge i8* [[C:%.*]], [[D:%.*]]
+; CHECK-NEXT:    [[C_3:%.*]] = icmp uge i8* [[C:%.*]], [[D:%.*]], !annotation !0
 ; CHECK-NEXT:    [[OR_COND:%.*]] = or i1 [[C_2_NOT]], [[C_3]]
 ; CHECK-NEXT:    br i1 [[OR_COND]], label [[TRAP:%.*]], label [[CONT1:%.*]], !annotation !0
 ; CHECK:       trap: ; preds = %entry
Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2884,11 +2884,15 @@
     Changed = true;
 
     IRBuilder<> Builder(PBI);
+    // The builder is used to create instructions to eliminate the branch in BB.
+    // If BB's terminator has !annotation metadata, add it to the new
+    // instructions.
+    Builder.CollectMetadataToCopy(BB->getTerminator(),
+                                  {LLVMContext::MD_annotation});
 
     // If we need to invert the condition in the pred block to match, do so now.
     if (InvertPredCond) {
       Value *NewCond = PBI->getCondition();
-
       if (NewCond->hasOneUse() && isa<CmpInst>(NewCond)) {
         CmpInst *CI = cast<CmpInst>(NewCond);
         CI->setPredicate(CI->getInversePredicate());
@@ -2939,8 +2943,9 @@
       // its potential value. The previous information might have been valid
       // only given the branch precondition.
       // For an analogous reason, we must also drop all the metadata whose
-      // semantics we don't understand.
-      NewBonusInst->dropUnknownNonDebugMetadata();
+      // semantics we don't understand. We *can* preserve !annotation, because
+      // it is tied to the instruction itself, not the value or position.
+      NewBonusInst->dropUnknownNonDebugMetadata(LLVMContext::MD_annotation);
 
       PredBlock->getInstList().insert(PBI->getIterator(), NewBonusInst);
       NewBonusInst->takeName(&BonusInst);


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