[llvm-branch-commits] [llvm] 700cf7d - [VNCoercion] Disallow coercion between different ni addrspaces

[Valentin Churavy via llvm-branch-commits]

Author: Valentin Churavy
Date: 2020-12-07T20:19:48-05:00
New Revision: 700cf7dcc927c0ffddc0a1acbfde490f673ffb4a

URL: https://github.com/llvm/llvm-project/commit/700cf7dcc927c0ffddc0a1acbfde490f673ffb4a
DIFF: https://github.com/llvm/llvm-project/commit/700cf7dcc927c0ffddc0a1acbfde490f673ffb4a.diff

LOG: [VNCoercion] Disallow coercion between different ni addrspaces

I'm not sure if it would be legal by the IR reference to introduce
an addrspacecast here, since the IR reference is a bit vague on
the exact semantics, but at least for our usage of it (and I
suspect for many other's usage) it is not. For us, addrspacecasts
between non-integral address spaces carry frontend information that the
optimizer cannot deduce afterwards in a generic way (though we
have frontend specific passes in our pipline that do propagate
these). In any case, I'm sure nobody is using it this way at
the moment, since it would have introduced inttoptrs, which
are definitely illegal.

Fixes PR38375

Co-authored-by: Keno Fischer <keno at alumni.harvard.edu>

Reviewed By: reames

Differential Revision: https://reviews.llvm.org/D50010

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/VNCoercion.cpp
    llvm/test/Transforms/GVN/non-integral-pointers.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/VNCoercion.cpp b/llvm/lib/Transforms/Utils/VNCoercion.cpp
index 3adb9d40b4ff..61cd8595a73b 100644
--- a/llvm/lib/Transforms/Utils/VNCoercion.cpp
+++ b/llvm/lib/Transforms/Utils/VNCoercion.cpp
@@ -37,23 +37,27 @@ bool canCoerceMustAliasedValueToLoad(Value *StoredVal, Type *LoadTy,
   if (StoreSize < DL.getTypeSizeInBits(LoadTy).getFixedSize())
     return false;
 
+  bool StoredNI = DL.isNonIntegralPointerType(StoredTy->getScalarType());
+  bool LoadNI = DL.isNonIntegralPointerType(LoadTy->getScalarType());
   // Don't coerce non-integral pointers to integers or vice versa.
-  if (DL.isNonIntegralPointerType(StoredVal->getType()->getScalarType()) !=
-      DL.isNonIntegralPointerType(LoadTy->getScalarType())) {
+  if (StoredNI != LoadNI) {
     // As a special case, allow coercion of memset used to initialize
     // an array w/null.  Despite non-integral pointers not generally having a
     // specific bit pattern, we do assume null is zero.
     if (auto *CI = dyn_cast<Constant>(StoredVal))
       return CI->isNullValue();
     return false;
+  } else if (StoredNI && LoadNI &&
+             StoredTy->getPointerAddressSpace() !=
+                 LoadTy->getPointerAddressSpace()) {
+    return false;
   }
 
 
   // The implementation below uses inttoptr for vectors of unequal size; we
   // can't allow this for non integral pointers. We could teach it to extract
   // exact subvectors if desired. 
-  if (DL.isNonIntegralPointerType(StoredTy->getScalarType()) &&
-      StoreSize != DL.getTypeSizeInBits(LoadTy).getFixedSize())
+  if (StoredNI && StoreSize != DL.getTypeSizeInBits(LoadTy).getFixedSize())
     return false;
 
   return true;

diff  --git a/llvm/test/Transforms/GVN/non-integral-pointers.ll b/llvm/test/Transforms/GVN/non-integral-pointers.ll
index 872b6648084e..56f9d3179c27 100644
--- a/llvm/test/Transforms/GVN/non-integral-pointers.ll
+++ b/llvm/test/Transforms/GVN/non-integral-pointers.ll
@@ -1,7 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -gvn -S < %s | FileCheck %s
 
-target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:4"
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:4:5"
 target triple = "x86_64-unknown-linux-gnu"
 
 define void @f0(i1 %alwaysFalse, i64 %val, i64* %loc) {
@@ -430,3 +430,20 @@ entry:
 
 declare void @use.v2(<2 x i64 addrspace(4)*>)
 declare void @use.v4(<4 x i64 addrspace(4)*>)
+ define i8 addrspace(5)* @multini(i1 %alwaysFalse, i8 addrspace(4)* %val, i8 addrspace(4)** %loc) {
+ ; CHECK-LABEL: @multini(
+ ; CHECK-NOT: inttoptr
+ ; CHECK-NOT: ptrtoint
+ ; CHECK-NOT: addrspacecast
+  entry:
+   store i8 addrspace(4)* %val, i8 addrspace(4)** %loc
+   br i1 %alwaysFalse, label %neverTaken, label %alwaysTaken
+
+  neverTaken:
+   %loc.bc = bitcast i8 addrspace(4)** %loc to i8 addrspace(5)**
+   %
diff erentas = load i8 addrspace(5)*, i8 addrspace(5)** %loc.bc
+   ret i8 addrspace(5)* %
diff erentas
+
+  alwaysTaken:
+   ret i8 addrspace(5)* null
+ }