[PATCH] llvm.noalias - isPointerDereferenceable should look through them

[hfinkel at anl.gov]

Hi chandlerc, reames,

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

http://reviews.llvm.org/D9384

Files:
  lib/Analysis/ValueTracking.cpp
  test/Analysis/ValueTracking/memory-dereferenceable.ll

Index: lib/Analysis/ValueTracking.cpp
===================================================================
--- lib/Analysis/ValueTracking.cpp
+++ lib/Analysis/ValueTracking.cpp
@@ -2960,12 +2960,15 @@
     return true;
   }
 
-  // For gc.relocate, look through relocations
-  if (const IntrinsicInst *I = dyn_cast<IntrinsicInst>(V))
+  if (const IntrinsicInst *I = dyn_cast<IntrinsicInst>(V)) {
     if (I->getIntrinsicID() == Intrinsic::experimental_gc_relocate) {
+      // For gc.relocate, look through relocations
       GCRelocateOperands RelocateInst(I);
       return isDereferenceablePointer(RelocateInst.derivedPtr(), DL, Visited);
+    } else if (I->getIntrinsicID() == Intrinsic::noalias) {
+      return isDereferenceablePointer(I->getOperand(0), DL, Visited);
     }
+  }
 
   if (const AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(V))
     return isDereferenceablePointer(ASC->getOperand(0), DL, Visited);
@@ -2983,7 +2986,8 @@
   Type *Ty = VTy->getPointerElementType();
   if (Ty->isSized()) {
     APInt Offset(DL.getTypeStoreSizeInBits(VTy), 0);
-    const Value *BV = V->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
+    const Value *BV = V->stripAndAccumulateInBoundsConstantOffsets(DL, Offset,
+                           /*LookThroughNoAlias*/true);
     
     if (Offset.isNonNegative())
       if (isDereferenceableFromAttribute(BV, Offset, Ty, DL))
Index: test/Analysis/ValueTracking/memory-dereferenceable.ll
===================================================================
--- test/Analysis/ValueTracking/memory-dereferenceable.ll
+++ test/Analysis/ValueTracking/memory-dereferenceable.ll
@@ -25,10 +25,17 @@
     %tok = tail call i32 (i1 ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_i1f(i1 ()* @return_i1, i32 0, i32 0, i32 0, i32 addrspace(1)* %dparam)
     %relocate = call i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32 %tok, i32 4, i32 4)
     %load4 = load i32, i32 addrspace(1)* %relocate
-    %nparam = getelementptr i32, i32 addrspace(1)* %dparam, i32 5
+    %dpa = call i32 addrspace(1)* @llvm.noalias.p1i32(i32 addrspace(1)* %dparam, metadata !1)
+    %nparam = getelementptr i32, i32 addrspace(1)* %dpa, i32 5
     %load5 = load i32, i32 addrspace(1)* %nparam
     ret void
 }
 
 declare i32 @llvm.experimental.gc.statepoint.p0f_i1f(i1 ()*, i32, i32, ...)
 declare i32 addrspace(1)* @llvm.experimental.gc.relocate.p1i32(i32, i32, i32)
+
+declare i32 addrspace(1)* @llvm.noalias.p1i32(i32 addrspace(1)*, metadata) nounwind
+
+!0 = !{!0, !"some domain"}
+!1 = !{!1, !0, !"some scope"}
+

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