[PATCH 09/27] [noalias] [CodeGen] Support lowering of noalias intrinsics

[jeroen.dobbelaere]

Summary

This is part of the series started by D68484.

Note: this is a stable point and tests should run fine with the patches applied up to this point.
Note: D68496 has been incorporated.

[lebedev.ri]

Looks ok.

[jeroen.dobbelaere]

Rebased

[jeroen.dobbelaere]

Rebased to c06b7e2ab5167ad031745a706204abed1aefd823 (July 14, 2020)

[jeroen.dobbelaere]

Rebased to 9fb46a452d4e5666828c95610ceac8dcd9e4ce16 (September 7, 2020)

[jeroen.dobbelaere]

Rebased to f8dbd61074176bae92ec360a093ac7bc498c9321.

llvm/lib/CodeGen/IntrinsicLowering.cpp

case Intrinsic::ptr_annotation:
     CI->replaceAllUsesWith(CI->getOperand(0));
     break;
 
   case Intrinsic::assume:
   case Intrinsic::experimental_noalias_scope_decl:
   case Intrinsic::var_annotation:
     break;   // Strip out these intrinsics
 
+  case Intrinsic::noalias_decl:
+  case Intrinsic::noalias:
+  case Intrinsic::provenance_noalias:
+  case Intrinsic::noalias_arg_guard:
+  case Intrinsic::noalias_copy_guard:
+    // Just forward the value
+    CI->replaceAllUsesWith(CI->getOperand(0));
+    break;
+
   case Intrinsic::memcpy: {
     Type *IntPtr = DL.getIntPtrType(Context);
     Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
                                         /* isSigned */ false);
     Value *Ops[3];
     Ops[0] = CI->getArgOperand(0);
     Ops[1] = CI->getArgOperand(1);
     Ops[2] = Size;

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

#include "llvm/IR/VPIntrinsics.def"
   case Intrinsic::objectsize:
     llvm_unreachable("llvm.objectsize.* should have been lowered already");
 
   case Intrinsic::is_constant:
     llvm_unreachable("llvm.is.constant.* should have been lowered already");
 
   case Intrinsic::annotation:
   case Intrinsic::ptr_annotation:
+  case Intrinsic::noalias:
   case Intrinsic::launder_invariant_group:
   case Intrinsic::strip_invariant_group:
+  case Intrinsic::provenance_noalias:
+  case Intrinsic::noalias_arg_guard:
+  case Intrinsic::noalias_copy_guard:
     // Drop the intrinsic, but forward the value
     setValue(&I, getValue(I.getOperand(0)));
     return;
 
+  case Intrinsic::noalias_decl:
+    // Generate a dummy value - it will never be used and should get optimized
+    // away
+    setValue(&I, DAG.getUNDEF(TLI.getPointerTy(DAG.getDataLayout())));
+    return;
+
   case Intrinsic::assume:
   case Intrinsic::experimental_noalias_scope_decl:
   case Intrinsic::var_annotation:
   case Intrinsic::sideeffect:
     // Discard annotate attributes, noalias scope declarations, assumptions, and
     // artificial side-effects.
     return;
 

llvm/test/CodeGen/Generic/noalias.ll

+; RUN: llc < %s
+
+define i32* @test(i32* %p) {
+  %p.decl = tail call i8* @llvm.noalias.decl.p0i8.p0p0i32.i32(i32** null, i32 0, metadata !0)
+  %v = call i32* @llvm.noalias.p0i32.p0i8.p0p0i32.i32(i32* %p, i8* %p.decl, i32** null, i32 0, metadata !0)
+  ret i32* %v
+}
+
+declare i8* @llvm.noalias.decl.p0i8.p0p0i32.i32(i32**, i32, metadata) argmemonly nounwind
+declare i32* @llvm.noalias.p0i32.p0i8.p0p0i32.i32(i32*, i8*, i32**, i32, metadata) argmemonly nounwind speculatable
+
+!0 = !{!0, !"some domain"}
+!1 = !{!1, !0, !"some scope"}

llvm/test/CodeGen/Generic/provenance.noalias.ll

+; RUN: llc < %s
+
+define i32* @test(i32* %p) {
+  %p.decl = tail call i8* @llvm.noalias.decl.p0i8.p0p0i32.i32(i32** null, i32 0, metadata !0)
+  %p.provenance = tail call i32* @llvm.provenance.noalias.p0i32.p0i8.p0p0i32.p0p0i32.i32(i32* %p, i8* %p.decl, i32** null, i32** undef, i32 0, metadata !0)
+  %p.guard = call i32* @llvm.noalias.arg.guard.p0i32.p0i32(i32* %p, i32* %p.provenance)
+  ret i32* %p.guard
+}
+
+declare i8* @llvm.noalias.decl.p0i8.p0p0i32.i32(i32**, i32, metadata) argmemonly nounwind
+declare i32* @llvm.provenance.noalias.p0i32.p0i8.p0p0i32.p0p0i32.i32(i32*, i8*, i32**, i32**, i32, metadata)  argmemonly nounwind speculatable
+declare i32* @llvm.noalias.arg.guard.p0i32.p0i32(i32*, i32*) nounwind readnone
+
+!0 = !{!0, !"some domain"}
+!1 = !{!1, !0, !"some scope"}