llvm.noalias - isPointerDereferenceable should look through them

[hfinkel]

Summary

This is part of the series started by D9375, and teaches isPointerDereferenceable to look through calls to llvm.noalias.

[reames]

Resigning as a reviewer to get a very stale review off my list of blocking tasks in phabricator. Please readd when desired.

[hfinkel]

Rebased.

[majnemer]

LGTM

lib/Analysis/Loads.cpp

104 ↗

(On Diff #63351)

const auto *

llvm/trunk/lib/Analysis/Loads.cpp

static bool isDereferenceableAndAlignedPointer(
   if (const GCRelocateInst *RelocateInst = dyn_cast<GCRelocateInst>(V))
     return isDereferenceableAndAlignedPointer(
         RelocateInst->getDerivedPtr(), Align, Size, DL, CtxI, DT, Visited);
 
   if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V))
     return isDereferenceableAndAlignedPointer(ASC->getOperand(0), Align, Size,
                                               DL, CtxI, DT, Visited);
 
+  if (auto CS = ImmutableCallSite(V))
+    if (const Value *RV = CS.getReturnedArgOperand())
+      return isDereferenceableAndAlignedPointer(RV, Align, Size, DL, CtxI, DT,
+                                                Visited);
+
   // If we don't know, assume the worst.
   return false;
 }
 
 bool llvm::isDereferenceableAndAlignedPointer(const Value *V, unsigned Align,
                                               const DataLayout &DL,
                                               const Instruction *CtxI,
                                               const DominatorTree *DT) {

llvm/trunk/test/Analysis/ValueTracking/memory-dereferenceable.ll

; CHECK: %dparam{{.*}}(aligned)
     %load3 = load i32, i32 addrspace(1)* %dparam
 
 ; CHECK: %relocate{{.*}}(aligned)
     %tok = tail call token (i64, i32, i1 ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_i1f(i64 0, i32 0, i1 ()* @return_i1, i32 0, i32 0, i32 0, i32 0, i32 addrspace(1)* %dparam)
     %relocate = call i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(token %tok, i32 7, i32 7)
     %load4 = load i32, i32 addrspace(1)* %relocate
 
 ; CHECK-NOT: %nparam
-    %nparam = getelementptr i32, i32 addrspace(1)* %dparam, i32 5
+    %dpa = call i32 addrspace(1)* @func1(i32 addrspace(1)* %dparam)
+    %nparam = getelementptr i32, i32 addrspace(1)* %dpa, i32 5
     %load5 = load i32, i32 addrspace(1)* %nparam
 
     ; Load from a non-dereferenceable load
 ; CHECK-NOT: %nd_load
     %nd_load = load i32*, i32** @globali32ptr
     %load6 = load i32, i32* %nd_load
 
     ; Load from a dereferenceable load

 
 if.end:
   ret void
 }
 
 declare token @llvm.experimental.gc.statepoint.p0f_i1f(i64, i32, i1 ()*, i32, i32, ...)
 declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(token, i32, i32)
 
+declare i32 addrspace(1)* @func1(i32 addrspace(1)* returned) nounwind argmemonly
+
 !0 = !{i64 4}
 !1 = !{i64 2}
 !2 = !{}