[PATCH] D107822: [InstCombine] Fold Int2Ptr/PtrToInt if the ptr is dereferenceable

[Krishna Kariya via Phabricator via llvm-commits]

Krishnakariya updated this revision to Diff 367951.
Krishnakariya marked an inline comment as done.
Krishnakariya added a comment.

Updated diff


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D107822/new/

https://reviews.llvm.org/D107822

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
@@ -75,18 +75,14 @@
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i8 [[XVAL]], [[YVAL]]
 ; CHECK-NEXT:    br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
 ; CHECK:       if.then:
-; CHECK-NEXT:    [[Y_I:%.*]] = ptrtoint i8* [[Y]] to i64
-; CHECK-NEXT:    [[Y_P:%.*]] = inttoptr i64 [[Y_I]] to i8*
-; 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:    [[Z_I:%.*]] = ptrtoint i8* [[Z:%.*]] to i64
 ; CHECK-NEXT:    [[Z_P:%.*]] = inttoptr i64 [[Z_I]] to i8*
 ; CHECK-NEXT:    br label [[CALL]]
 ; CHECK:       call:
-; CHECK-NEXT:    [[PHI_1:%.*]] = phi i8* [ [[Z_P]], [[IF_ELSE]] ], [ [[Y_P]], [[IF_THEN]] ]
-; CHECK-NEXT:    [[PHI_2:%.*]] = phi i8* [ [[Z_P]], [[IF_ELSE]] ], [ [[X_P]], [[IF_THEN]] ]
+; CHECK-NEXT:    [[PHI_1:%.*]] = phi i8* [ [[Z_P]], [[IF_ELSE]] ], [ [[Y]], [[IF_THEN]] ]
+; CHECK-NEXT:    [[PHI_2:%.*]] = phi i8* [ [[Z_P]], [[IF_ELSE]] ], [ [[X]], [[IF_THEN]] ]
 ; CHECK-NEXT:    tail call void @foo(i8* [[PHI_1]], i8* [[PHI_2]])
 ; CHECK-NEXT:    ret void
 ;
@@ -124,9 +120,7 @@
 ; CHECK-NEXT:    [[YVAL:%.*]] = load i8, i8* [[Y:%.*]], align 1
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
 ; CHECK:       for.body:
-; CHECK-NEXT:    [[PHI:%.*]] = phi i8* [ [[X_P:%.*]], [[FOR_BODY]] ], [ [[Y]], [[FOR_BODY_PREHEADER]] ]
-; CHECK-NEXT:    [[X_I:%.*]] = ptrtoint i8* [[X]] to i64
-; CHECK-NEXT:    [[X_P]] = inttoptr i64 [[X_I]] to i8*
+; CHECK-NEXT:    [[PHI:%.*]] = phi i8* [ [[X]], [[FOR_BODY]] ], [ [[Y]], [[FOR_BODY_PREHEADER]] ]
 ; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i8 [[XVAL]], [[YVAL]]
 ; CHECK-NEXT:    br i1 [[CMP1]], label [[FOR_BODY]], label [[FOR_END]]
 ; CHECK:       for.end:
Index: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -344,6 +344,34 @@
     if (isDereferenceableAndAlignedPointer(Ptr, Align(1), APInt(64, 1), DL)) {
       return new BitCastInst(Ptr, CI.getDestTy());
     }
+    // Vector to find out all target users of roundtrip (int2ptr/ptr2int) cast
+    // which are dominated by load/store instruction of same address as of
+    // roundtripcast.
+    SmallVector<User *> TargetUsers;
+    Instruction *I;
+    for (auto *CU : CI.users()) {
+      if (!(I = dyn_cast<Instruction>(CU)))
+        continue;
+      int NumIterations = 0;
+      for (auto *U : Ptr->users()) {
+        if (NumIterations == 10)
+          goto DoneWithUsers;
+        NumIterations++;
+        if ((isa<LoadInst>(U) || isa<StoreInst>(U)) &&
+            DT.dominates(cast<Instruction>(U), I)) {
+          TargetUsers.push_back(CU);
+          break;
+        }
+      }
+    }
+  DoneWithUsers:
+    if (!TargetUsers.empty()) {
+      Value *BitCast = Builder.CreateBitCast(Ptr, CI.getDestTy());
+      for (auto *U : TargetUsers) {
+        U->replaceUsesOfWith(&CI, BitCast);
+      }
+      return &CI;
+    }
   }
   return nullptr;
 }


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