[NewGVN] add context instruction for SimplifyQuery

NewGVN will find operator from other context. ValueTracking currently doesn't have a way to run completely without context instruction.
So it will use operator itself as conext instruction.
If the operator in another branch will never be executed but it has an assume, it may caused value tracking use the assume to do wrong simpilfy.

It would be better to make these simplification queries not use context at all, but that would require some API changes.
For now we just use the orignial instruction as context instruction to fix the issue.

Fix llvm#56039

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D127942

Author: bcl5980

llvm/lib/Transforms/Scalar/NewGVN.cpp

@@ -1074,6 +1074,9 @@ const Expression *NewGVN::createBinaryExpression(unsigned Opcode, Type *T,
                                                  Value *Arg1, Value *Arg2,
                                                  Instruction *I) const {
   auto *E = new (ExpressionAllocator) BasicExpression(2);
+  // TODO: we need to remove context instruction after Value Tracking
+  // can run without context instruction
+  const SimplifyQuery Q = SQ.getWithInstruction(I);
 
   E->setType(T);
   E->setOpcode(Opcode);
@@ -1089,7 +1092,7 @@ const Expression *NewGVN::createBinaryExpression(unsigned Opcode, Type *T,
   E->op_push_back(lookupOperandLeader(Arg1));
   E->op_push_back(lookupOperandLeader(Arg2));
 
-  Value *V = simplifyBinOp(Opcode, E->getOperand(0), E->getOperand(1), SQ);
+  Value *V = simplifyBinOp(Opcode, E->getOperand(0), E->getOperand(1), Q);
   if (auto Simplified = checkExprResults(E, I, V)) {
     addAdditionalUsers(Simplified, I);
     return Simplified.Expr;
@@ -1145,6 +1148,9 @@ NewGVN::ExprResult NewGVN::checkExprResults(Expression *E, Instruction *I,
 
 NewGVN::ExprResult NewGVN::createExpression(Instruction *I) const {
   auto *E = new (ExpressionAllocator) BasicExpression(I->getNumOperands());
+  // TODO: we need to remove context instruction after Value Tracking
+  // can run without context instruction
+  const SimplifyQuery Q = SQ.getWithInstruction(I);
 
   bool AllConstant = setBasicExpressionInfo(I, E);
 
@@ -1173,7 +1179,7 @@ NewGVN::ExprResult NewGVN::createExpression(Instruction *I) const {
     assert((E->getOperand(0)->getType() == I->getOperand(0)->getType() &&
             E->getOperand(1)->getType() == I->getOperand(1)->getType()));
     Value *V =
-        simplifyCmpInst(Predicate, E->getOperand(0), E->getOperand(1), SQ);
+        simplifyCmpInst(Predicate, E->getOperand(0), E->getOperand(1), Q);
     if (auto Simplified = checkExprResults(E, I, V))
       return Simplified;
   } else if (isa<SelectInst>(I)) {
@@ -1182,25 +1188,25 @@ NewGVN::ExprResult NewGVN::createExpression(Instruction *I) const {
       assert(E->getOperand(1)->getType() == I->getOperand(1)->getType() &&
              E->getOperand(2)->getType() == I->getOperand(2)->getType());
       Value *V = simplifySelectInst(E->getOperand(0), E->getOperand(1),
-                                    E->getOperand(2), SQ);
+                                    E->getOperand(2), Q);
       if (auto Simplified = checkExprResults(E, I, V))
         return Simplified;
     }
   } else if (I->isBinaryOp()) {
     Value *V =
-        simplifyBinOp(E->getOpcode(), E->getOperand(0), E->getOperand(1), SQ);
+        simplifyBinOp(E->getOpcode(), E->getOperand(0), E->getOperand(1), Q);
     if (auto Simplified = checkExprResults(E, I, V))
       return Simplified;
   } else if (auto *CI = dyn_cast<CastInst>(I)) {
     Value *V =
-        simplifyCastInst(CI->getOpcode(), E->getOperand(0), CI->getType(), SQ);
+        simplifyCastInst(CI->getOpcode(), E->getOperand(0), CI->getType(), Q);
     if (auto Simplified = checkExprResults(E, I, V))
       return Simplified;
   } else if (auto *GEPI = dyn_cast<GetElementPtrInst>(I)) {
     Value *V =
         simplifyGEPInst(GEPI->getSourceElementType(), *E->op_begin(),
                         makeArrayRef(std::next(E->op_begin()), E->op_end()),
-                        GEPI->isInBounds(), SQ);
+                        GEPI->isInBounds(), Q);
     if (auto Simplified = checkExprResults(E, I, V))
       return Simplified;
   } else if (AllConstant) {

llvm/test/Transforms/NewGVN/sq-ctxi.ll

@@ -0,0 +1,46 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes=newgvn -S | FileCheck %s
+
+; github issue #56039
+define i8 @src(i8* %a, i8* %b, i1 %c) {
+; CHECK-LABEL: @src(
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[BB1:%.*]], label [[BB2:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[LB1:%.*]] = load i8, i8* [[B:%.*]], align 1
+; CHECK-NEXT:    [[TOBOOL3_NOT_I:%.*]] = icmp eq i8 [[LB1]], 0
+; CHECK-NEXT:    br i1 [[TOBOOL3_NOT_I]], label [[BB4:%.*]], label [[BB3:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[LB2:%.*]] = load i8, i8* [[B]], align 1
+; CHECK-NEXT:    [[CMP_NOT_I:%.*]] = icmp ult i8 0, [[LB2]]
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[CMP_NOT_I]])
+; CHECK-NEXT:    br label [[BB3]]
+; CHECK:       bb3:
+; CHECK-NEXT:    [[LA:%.*]] = load i8, i8* [[A:%.*]], align 1
+; CHECK-NEXT:    br label [[BB4]]
+; CHECK:       bb4:
+; CHECK-NEXT:    ret i8 0
+;
+  br i1 %c, label %bb1, label %bb2
+
+bb1:
+  %lb1 = load i8, i8* %b
+  %tobool3.not.i = icmp eq i8 %lb1, 0
+  br i1 %tobool3.not.i, label %bb4, label %bb3
+
+bb2:
+  %lb2 = load i8, i8* %b
+  %cmp.not.i = icmp ult i8 0, %lb2
+  tail call void @llvm.assume(i1 %cmp.not.i)
+  br label %bb3
+
+bb3:
+  %p = phi i8 [ %lb1, %bb1 ], [ %lb2, %bb2 ]
+  %la = load i8, i8* %a
+  %xor = xor i8 %la, %p
+  br label %bb4
+
+bb4:
+  ret i8 0
+}
+
+declare void @llvm.assume(i1)