[GVN] Add missing ICF update

[aeubanks]

Summary

performScalarPREInsertion() inserts instructions into blocks that we
need to tell ImplicitControlFlowTracking about, otherwise the ICF cache
may be invalid.

Fixes PR49193.

[nikic]

LGTM

llvm/lib/Transforms/Scalar/GVN.cpp

bool GVN::performScalarPREInsertion(Instruction *Instr, BasicBlock *Pred,
   // are not value numbered precisely.
   if (!success)
     return false;
 
   Instr->insertBefore(Pred->getTerminator());
   Instr->setName(Instr->getName() + ".pre");
   Instr->setDebugLoc(Instr->getDebugLoc());
 
+  ICF->insertInstructionTo(Instr, Pred);
+
   unsigned Num = VN.lookupOrAdd(Instr);
   VN.add(Instr, Num);
 
   // Update the availability map to include the new instruction.
   addToLeaderTable(Num, Instr, Pred);
   return true;
 }
 

llvm/test/Transforms/GVN/pr49193.ll

+; RUN: opt -passes=gvn -S < %s | FileCheck %s
+
+@a = external local_unnamed_addr global i32, align 4
+@b = external local_unnamed_addr global i32, align 4
+
+; Function Attrs: nounwind readnone
+declare i32* @j() local_unnamed_addr #0
+
+; CHECK: define {{.*}}@k()
+
+define i64 @k() local_unnamed_addr {
+bb:
+  br i1 undef, label %bb10.preheader, label %bb3
+
+bb10.preheader:                                   ; preds = %bb
+  br label %bb13
+
+bb3:                                              ; preds = %bb
+  %i4 = load i32, i32* @a, align 4
+  %i5.not = icmp eq i32 %i4, 0
+  br label %bb7
+
+bb7:                                              ; preds = %bb3
+  %i8 = tail call i32* @j()
+  br label %bb37
+
+bb13:                                             ; preds = %bb34, %bb10.preheader
+  br i1 undef, label %bb30thread-pre-split, label %bb16
+
+bb16:                                             ; preds = %bb13
+  %i17 = tail call i32* @j()
+  br i1 undef, label %bb22thread-pre-split, label %bb37.loopexit
+
+bb22thread-pre-split:                             ; preds = %bb16
+  br label %bb27
+
+bb27:                                             ; preds = %bb22thread-pre-split
+  br i1 undef, label %bb30thread-pre-split, label %bb37.loopexit
+
+bb30thread-pre-split:                             ; preds = %bb27, %bb13
+  %i31.pr = load i32, i32* @a, align 4
+  %i32.not2 = icmp eq i32 %i31.pr, 0
+  br label %bb34
+
+bb34:                                             ; preds = %bb30thread-pre-split
+  br i1 undef, label %bb37.loopexit, label %bb13
+
+bb37.loopexit:                                    ; preds = %bb34, %bb27, %bb16
+  br label %bb37
+
+bb37:                                             ; preds = %bb37.loopexit, %bb7
+  %i38 = load i32, i32* @a, align 4
+  store i32 %i38, i32* @b, align 4
+  %i39 = tail call i32* @j()
+  unreachable
+}
+
+attributes #0 = { nounwind readnone }