llvm.noalias - don't interfere with llvm.assume

[hfinkel]

Summary

This is part of the series started by D9375, and adds llvm.noalias to the list of intrinsics ignored when searching for relevant assumptions (it can be ignored because it can't trap, etc.).

[reames]

LGTM. Two entirely optional comments, no further review needed.

lib/Analysis/ValueTracking.cpp

393

If you're touching this code anyways, please update the name to something more clear?

398

Is it time to common these two lists?

[hfinkel]

lib/Analysis/ValueTracking.cpp

393

Suggestions for a better name?

398

Yes. I'll do that in a separate patch.

[hfinkel]

Rebased.

[majnemer]

LGTM

[hfinkel]

Rebased

[hfinkel]

Rebased.

lib/Analysis/ValueTracking.cpp

if (!FoundNEUse) {
         }
     }
   }
 
   return false;
 }
 
 // Is this an intrinsic that cannot be speculated but also cannot trap?
 static bool isAssumeLikeIntrinsic(const Instruction *I) {
   if (const CallInst *CI = dyn_cast<CallInst>(I))
     if (Function *F = CI->getCalledFunction())
       switch (F->getIntrinsicID()) {
       default: break;
       // FIXME: This list is repeated from NoTTI::getIntrinsicCost.
       case Intrinsic::assume:
       case Intrinsic::dbg_declare:
       case Intrinsic::dbg_value:
       case Intrinsic::invariant_start:
       case Intrinsic::invariant_end:
       case Intrinsic::lifetime_start:
       case Intrinsic::lifetime_end:
+      case Intrinsic::noalias:
       case Intrinsic::objectsize:
       case Intrinsic::ptr_annotation:
       case Intrinsic::var_annotation:
         return true;
       }
 
   return false;
 }

test/Transforms/InstCombine/assume.ll

entry:
   %rval = icmp eq i32* %load, null
   ret i1 %rval
 
 ; CHECK-LABEL: @nonnull4
 ; CHECK-NOT: !nonnull
 ; CHECK: call void @llvm.assume
 }
 
+define i1 @nonnull5(i32** %a) {
+entry:
+  %load = load i32*, i32** %a
+  ;; This call cannot actually trap, and so should not disrupt the assume.
+  %v = call i32* @llvm.noalias.p0i32(i32* %load, metadata !1)
+  %cmp = icmp ne i32* %load, null
+  tail call void @llvm.assume(i1 %cmp)
+  %q = bitcast i32** %a to i32*
+  %rval = icmp eq i32* %v, %q
+  ret i1 %rval
+
+; CHECK-LABEL: @nonnull5
+; CHECK: !nonnull
+; CHECK-NOT: call void @llvm.assume
+}
 
+declare i32* @llvm.noalias.p0i32(i32*, metadata) nounwind
 
+!0 = !{!0, !"some domain"}
+!1 = !{!1, !0, !"some scope"}
 
 attributes #0 = { nounwind uwtable }
 attributes #1 = { nounwind }