[PATCH] D46972: Propagate nonnull and dereferenceable throught launder

[Piotr Padlewski via Phabricator via llvm-commits]

Prazek created this revision.
Prazek added reviewers: rsmith, amharc, kuhar, xbolva00, hfinkel.
Herald added a subscriber: hiraditya.

invariant.group.launder should not stop propagation
of nonnull and dereferenceable, because e.g. we would not be
able to hoist loads speculatively.


Repository:
  rL LLVM

https://reviews.llvm.org/D46972

Files:
  llvm/lib/Analysis/Loads.cpp
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/test/Analysis/ValueTracking/deref-bitcast-of-gep.ll
  llvm/test/Analysis/ValueTracking/invariant.group.ll


Index: llvm/test/Analysis/ValueTracking/invariant.group.ll
===================================================================
--- /dev/null
+++ llvm/test/Analysis/ValueTracking/invariant.group.ll
@@ -0,0 +1,19 @@
+; RUN: opt -S -instsimplify -instcombine < %s | FileCheck %s
+
+; CHECK-LABEL: define void @checkNonnull()
+define void @checkNonnull() {
+; CHECK:   %p = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %0)
+; CHECK:   %p2 = call i8* @llvm.launder.invariant.group.p0i8(i8* nonnull %p)
+; CHECK:   call void @use(i8* nonnull %p2)
+entry:
+  %0 = alloca i8, align 8
+
+  %p = call i8* @llvm.launder.invariant.group.p0i8(i8* %0)
+  %p2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %p)
+  call void @use(i8* %p2)
+
+  ret void
+}
+
+declare i8* @llvm.launder.invariant.group.p0i8(i8*)
+declare void @use(i8*)
Index: llvm/test/Analysis/ValueTracking/deref-bitcast-of-gep.ll
===================================================================
--- llvm/test/Analysis/ValueTracking/deref-bitcast-of-gep.ll
+++ llvm/test/Analysis/ValueTracking/deref-bitcast-of-gep.ll
@@ -80,3 +80,28 @@
 leave:
   ret void
 }
+
+define void @checkLaunder(i8* align 4 dereferenceable(1024) %p) {
+; CHECK-LABEL: @checkLaunder(
+; CHECK: entry:
+; CHECK:  %l = call i8* @llvm.launder.invariant.group.p0i8(i8* %p)
+; CHECK:  %val = load i8, i8* %l
+; CHECK:  br label %loop
+; CHECK: loop:
+; CHECK:  call void @use(i32 0)
+; CHECK-NEXT:  call void @use8(i8 %val)
+
+entry:
+  %l = call i8* @llvm.launder.invariant.group.p0i8(i8* %p)
+  br label %loop
+
+loop:
+  call void @use(i32 0)
+  %val = load i8, i8* %l, !invariant.load !{}
+  call void @use8(i8 %val)
+  br label %loop
+}
+
+declare i8* @llvm.launder.invariant.group.p0i8(i8*)
+
+declare void @use8(i8)
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -1953,9 +1953,12 @@
       if (LI->getMetadata(LLVMContext::MD_nonnull))
         return true;
 
-    if (auto CS = ImmutableCallSite(V))
+    if (auto CS = ImmutableCallSite(V)) {
       if (CS.isReturnNonNull())
         return true;
+      if (CS.getIntrinsicID() == Intrinsic::ID::launder_invariant_group)
+        return isKnownNonZero(CS->getOperand(0), Depth + 1, Q);
+    }
   }
 
   // The remaining tests are all recursive, so bail out if we hit the limit.
Index: llvm/lib/Analysis/Loads.cpp
===================================================================
--- llvm/lib/Analysis/Loads.cpp
+++ llvm/lib/Analysis/Loads.cpp
@@ -107,11 +107,14 @@
     return isDereferenceableAndAlignedPointer(ASC->getOperand(0), Align, Size,
                                               DL, CtxI, DT, Visited);
 
-  if (auto CS = ImmutableCallSite(V))
+  if (auto CS = ImmutableCallSite(V)) {
     if (const Value *RV = CS.getReturnedArgOperand())
       return isDereferenceableAndAlignedPointer(RV, Align, Size, DL, CtxI, DT,
                                                 Visited);
-
+    if (CS.getIntrinsicID() == Intrinsic::launder_invariant_group)
+      return isDereferenceableAndAlignedPointer(CS->getOperand(0), Align, Size,
+                                                DL, CtxI, DT, Visited);
+  }
   // If we don't know, assume the worst.
   return false;
 }


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