[PATCH] D108506: [InstCombine] Fold Int2Ptr/PtrToInt if the ptr is dereferenceable using API

[Krishna Kariya via Phabricator via llvm-commits]

Krishnakariya created this revision.
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Split from D107822 <https://reviews.llvm.org/D107822>.
In this patch, we remove the roundtrip cast if p is dereferenceable. 
We check whether p is dereferenceable using the "isDereferenceableAndAlignedPointer" API.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D108506

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
  llvm/test/Transforms/InstCombine/load-int2ptr-fold.ll


Index: llvm/test/Transforms/InstCombine/load-int2ptr-fold.ll
===================================================================
--- llvm/test/Transforms/InstCombine/load-int2ptr-fold.ll
+++ llvm/test/Transforms/InstCombine/load-int2ptr-fold.ll
@@ -10,13 +10,13 @@
 ; CHECK-LABEL: @test_dereferenceable(
 ; CHECK-NEXT:    br i1 [[CMP:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
 ; CHECK:       if.then:
+; CHECK-NEXT:    [[X_I:%.*]] = ptrtoint i8* [[X:%.*]] to i64
+; CHECK-NEXT:    [[X_P:%.*]] = inttoptr i64 [[X_I]] to i8*
 ; CHECK-NEXT:    br label [[CALL:%.*]]
 ; CHECK:       if.else:
 ; CHECK-NEXT:    br label [[CALL]]
 ; CHECK:       call:
-; CHECK-NEXT:    [[PHI_1_IN_IN:%.*]] = phi i8* [ [[Z:%.*]], [[IF_ELSE]] ], [ [[X:%.*]], [[IF_THEN]] ]
-; CHECK-NEXT:    [[PHI_1_IN:%.*]] = ptrtoint i8* [[PHI_1_IN_IN]] to i64
-; CHECK-NEXT:    [[PHI_1:%.*]] = inttoptr i64 [[PHI_1_IN]] to i8*
+; CHECK-NEXT:    [[PHI_1:%.*]] = phi i8* [ [[Z:%.*]], [[IF_ELSE]] ], [ [[X_P]], [[IF_THEN]] ]
 ; CHECK-NEXT:    tail call void @foo(i8* [[PHI_1]], i8* [[PHI_1]])
 ; CHECK-NEXT:    ret void
 ;
@@ -46,9 +46,7 @@
 ; CHECK:       if.else:
 ; CHECK-NEXT:    br label [[CALL]]
 ; CHECK:       call:
-; CHECK-NEXT:    [[PHI_1_IN_IN:%.*]] = phi i8* [ [[Z:%.*]], [[IF_ELSE]] ], [ [[X:%.*]], [[IF_THEN]] ]
-; CHECK-NEXT:    [[PHI_1_IN:%.*]] = ptrtoint i8* [[PHI_1_IN_IN]] to i64
-; CHECK-NEXT:    [[PHI_1:%.*]] = inttoptr i64 [[PHI_1_IN]] to i8*
+; CHECK-NEXT:    [[PHI_1:%.*]] = phi i8* [ [[Z:%.*]], [[IF_ELSE]] ], [ [[X:%.*]], [[IF_THEN]] ]
 ; CHECK-NEXT:    tail call void @foo(i8* nonnull [[PHI_1]], i8* nonnull [[PHI_1]])
 ; CHECK-NEXT:    ret void
 ;
Index: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -13,6 +13,7 @@
 #include "InstCombineInternal.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/Loads.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/DataLayout.h"
@@ -336,7 +337,14 @@
       return new ShuffleVectorInst(CastX, UndefValue::get(DestTy), Mask);
     }
   }
-
+  // Replace Int2Ptr/Ptr2Int RoundTrip Cast with bitcast if the pointer
+  // is dereferenceable.
+  Value *Ptr = isIntToPtrRoundTripCast(&CI);
+  if (Ptr) {
+    if (isDereferenceableAndAlignedPointer(Ptr, Align(1), APInt(64, 1), DL)) {
+      return new BitCastInst(Ptr, CI.getDestTy());
+    }
+  }
   return nullptr;
 }
 


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