[GlobalOpt] Fix the assert for null check of global value

[scui]

Summary

This is to fix the reported assert - https://bugs.llvm.org/show_bug.cgi?id=51608.

[asbirlea]

Thanks you for the fix!
The unreduced reproducer no longer asserts with it.

llvm/lib/Transforms/IPO/GlobalOpt.cpp

if (isa<LoadInst>(U)) {
       // If we've already seen this phi node, ignore it, it has already been
       // checked.
       if (PHIs.insert(PN).second && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
         return false;
     } else if (isa<ICmpInst>(U) &&
                !ICmpInst::isSigned(cast<ICmpInst>(U)->getPredicate()) &&
                isa<LoadInst>(U->getOperand(0)) &&
                isa<ConstantPointerNull>(U->getOperand(1))) {
-      assert(isa<GlobalValue>(
-                 cast<LoadInst>(U->getOperand(0))->getPointerOperand()) &&
+      assert(isa<GlobalValue>(cast<LoadInst>(U->getOperand(0))
+                                  ->getPointerOperand()
+                                  ->stripPointerCasts()) &&
              "Should be GlobalVariable");
       // This and only this kind of non-signed ICmpInst is to be replaced with
       // the comparing of the value of the created global init bool later in
       // optimizeGlobalAddressOfMalloc for the global variable.
     } else {
       //cerr << "NONTRAPPING USE: " << *U;
       return false;
     }

llvm/test/Transforms/GlobalOpt/null-check-global-value.ll

+; RUN: opt -globalopt -S < %s | FileCheck %s
+
+%sometype = type { i8* }
+
+@map = internal unnamed_addr global %sometype* null, align 8
+
+define void @Init() {
+; CHECK-LABEL: @Init(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    store i1 true, i1* @map.init, align 1
+; CHECK-NEXT:    ret void
+;
+entry:
+  %call = tail call noalias nonnull dereferenceable(48) i8* @_Znwm(i64 48)
+  store i8* %call, i8** bitcast (%sometype** @map to i8**), align 8
+  ret void
+}
+
+define void @Usage() {
+; CHECK-LABEL: @Usage(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[MAP_INIT_VAL:%.*]] = load i1, i1* @map.init, align 1
+; CHECK-NEXT:    [[NOTINIT:%.*]] = xor i1 [[MAP_INIT_VAL]], true
+; CHECK-NEXT:    unreachable
+;
+entry:
+  %0 = load i8*, i8** bitcast (%sometype** @map to i8**), align 8
+  %.not = icmp eq i8* %0, null
+  unreachable
+}
+
+declare i8* @_Znwm(i64)