[CVP] Make select fold use-site specific (PR63756)

We may be able to replace the select with one of its select arms
at some but not all uses.

For uses in phi nodes this was already handled in the getValueOnEdge()
fold (which we can't drop entirely because it also handles an additional
case).

Fixes #63756.

llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp

@@ -95,22 +95,32 @@ STATISTIC(NumUDivURemsNarrowedExpanded,
           "Number of bound udiv's/urem's expanded");
 
 static bool processSelect(SelectInst *S, LazyValueInfo *LVI) {
-  if (S->getType()->isVectorTy()) return false;
-  if (isa<Constant>(S->getCondition())) return false;
+  if (S->getType()->isVectorTy() || isa<Constant>(S->getCondition()))
+    return false;
 
-  Constant *C = LVI->getConstant(S->getCondition(), S);
-  if (!C) return false;
+  bool Changed = false;
+  for (Use &U : make_early_inc_range(S->uses())) {
+    auto *I = cast<Instruction>(U.getUser());
+    Constant *C;
+    if (auto *PN = dyn_cast<PHINode>(I))
+      C = LVI->getConstantOnEdge(S->getCondition(), PN->getIncomingBlock(U),
+                                 I->getParent(), I);
+    else
+      C = LVI->getConstant(S->getCondition(), I);
 
-  ConstantInt *CI = dyn_cast<ConstantInt>(C);
-  if (!CI) return false;
+    auto *CI = dyn_cast_or_null<ConstantInt>(C);
+    if (!CI)
+      continue;
 
-  Value *ReplaceWith = CI->isOne() ? S->getTrueValue() : S->getFalseValue();
-  S->replaceAllUsesWith(ReplaceWith);
-  S->eraseFromParent();
+    U.set(CI->isOne() ? S->getTrueValue() : S->getFalseValue());
+    Changed = true;
+    ++NumSelects;
+  }
 
-  ++NumSelects;
+  if (Changed && S->use_empty())
+    S->eraseFromParent();
 
-  return true;
+  return Changed;
 }
 
 /// Try to simplify a phi with constant incoming values that match the edge

llvm/test/Transforms/CorrelatedValuePropagation/select.ll

@@ -7,7 +7,6 @@ define i8 @simple_phi(i1 %c, i8 %a, i8 %b) {
 ; CHECK-LABEL: define i8 @simple_phi
 ; CHECK-SAME: (i1 [[C:%.*]], i8 [[A:%.*]], i8 [[B:%.*]]) {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[C]], i8 [[A]], i8 [[B]]
 ; CHECK-NEXT:    br i1 [[C]], label [[THEN:%.*]], label [[ELSE:%.*]]
 ; CHECK:       then:
 ; CHECK-NEXT:    ret i8 [[A]]
@@ -36,7 +35,6 @@ define i8 @phi_other_edge(i1 %c, i8 %a, i8 %b, i32 %sw) {
 ; CHECK-NEXT:    i32 1, label [[ELSE:%.*]]
 ; CHECK-NEXT:    ]
 ; CHECK:       test:
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[C]], i8 [[A]], i8 [[B]]
 ; CHECK-NEXT:    br i1 [[C]], label [[THEN]], label [[ELSE]]
 ; CHECK:       then:
 ; CHECK-NEXT:    [[PHI1:%.*]] = phi i8 [ [[A]], [[TEST]] ], [ 1, [[ENTRY:%.*]] ]
@@ -96,12 +94,11 @@ define i8 @simple_non_phi(i1 %c, i8 %a, i8 %b) {
 ; CHECK-LABEL: define i8 @simple_non_phi
 ; CHECK-SAME: (i1 [[C:%.*]], i8 [[A:%.*]], i8 [[B:%.*]]) {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[S:%.*]] = select i1 [[C]], i8 [[A]], i8 [[B]]
 ; CHECK-NEXT:    br i1 [[C]], label [[THEN:%.*]], label [[ELSE:%.*]]
 ; CHECK:       then:
-; CHECK-NEXT:    ret i8 [[S]]
+; CHECK-NEXT:    ret i8 [[A]]
 ; CHECK:       else:
-; CHECK-NEXT:    ret i8 [[S]]
+; CHECK-NEXT:    ret i8 [[B]]
 ;
 entry:
   %s = select i1 %c, i8 %a, i8 %b
@@ -123,10 +120,10 @@ define void @simple_multiple_uses(i1 %c, i8 %a, i8 %b) {
 ; CHECK-NEXT:    call void @use(i8 [[S]], i8 [[S]])
 ; CHECK-NEXT:    br i1 [[C]], label [[THEN:%.*]], label [[ELSE:%.*]]
 ; CHECK:       then:
-; CHECK-NEXT:    call void @use(i8 [[S]], i8 [[S]])
+; CHECK-NEXT:    call void @use(i8 [[A]], i8 [[A]])
 ; CHECK-NEXT:    ret void
 ; CHECK:       else:
-; CHECK-NEXT:    call void @use(i8 [[S]], i8 [[S]])
+; CHECK-NEXT:    call void @use(i8 [[B]], i8 [[B]])
 ; CHECK-NEXT:    ret void
 ;
 entry: