[Attributor] Bitcast constant to the returned value type if it has different type

[sdmitriev]

llvm/lib/Transforms/IPO/AttributorAttributes.cpp

4536

I probably should not change captured C. I will upload an updated patch.

[jdoerfert]

LGTM.

llvm/lib/Transforms/IPO/AttributorAttributes.cpp

if (C) {
           [&](Value &V, const SmallSetVector<ReturnInst *, 4> &RetInsts) {
             // We can replace the AssociatedValue with the constant.
             if (&V == C || V.getType() != C->getType() || isa<UndefValue>(V))
               return true;
 
             for (ReturnInst *RI : RetInsts) {
               if (RI->getFunction() != getAnchorScope())
                 continue;
-              LLVM_DEBUG(dbgs() << "[ValueSimplify] " << V << " -> " << *C
+              auto *RC = C;
+              if (RC->getType() != RI->getReturnValue()->getType())
+                RC = ConstantExpr::getBitCast(RC,
+                                              RI->getReturnValue()->getType());
+              LLVM_DEBUG(dbgs() << "[ValueSimplify] " << V << " -> " << *RC
                                 << " in " << *RI << " :: " << *this << "\n");
-              if (A.changeUseAfterManifest(RI->getOperandUse(0), *C))
+              if (A.changeUseAfterManifest(RI->getOperandUse(0), *RC))
                 Changed = ChangeStatus::CHANGED;
             }
             return true;
           };
       A.checkForAllReturnedValuesAndReturnInsts(PredForReturned, *this);
     }
 
     return Changed | AAValueSimplify::manifest(A);

llvm/test/Transforms/Attributor/returned_crash.ll

 ; RUN: opt -attributor -S %s | FileCheck %s
 ; RUN: opt -passes=attributor -S %s | FileCheck %s
-;
-; CHECK: define i32 addrspace(1)* @foo(i32 addrspace(4)* nofree readnone %arg)
+
+@var = internal global [1 x i32] undef
+
+; CHECK-LABEL: define i32 addrspace(1)* @foo(i32 addrspace(4)* nofree readnone %arg)
 define i32 addrspace(1)* @foo(i32 addrspace(4)* %arg) {
 entry:
   %0 = addrspacecast i32 addrspace(4)* %arg to i32 addrspace(1)*
   ret i32 addrspace(1)* %0
 }
+
+define i32* @func1() {
+  %ptr = call i32* @func1a([1 x i32]* @var)
+  ret i32* %ptr
+}
+
+; CHECK-LABEL: define internal nonnull align 4 dereferenceable(4) i32* @func1a()
+; CHECK-NEXT: ret i32* getelementptr inbounds ([1 x i32], [1 x i32]* @var, i32 0, i32 0)
+define internal i32* @func1a([1 x i32]* %arg) {
+  %ptr = getelementptr inbounds [1 x i32], [1 x i32]* %arg, i64 0, i64 0
+  ret i32* %ptr
+}