[LLVMbugs] [Bug 15907] New: SROA pass introduces bitcast between different address spaces

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=15907

            Bug ID: 15907
           Summary: SROA pass introduces bitcast between different address
                    spaces
           Product: new-bugs
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: mpfergu at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Hi -

I'm having a problem with SROA removing important (to me) address space
information with a bitcast. Help is appreciated, thanks!

To reproduce, run the below small test case through opt -sroa -S ... you will
see in the output the bitcast is added; with 3.2 we get lines like:
  %a.0.storeme.cast.cast = bitcast i8 addrspace(100)* %storeme.cast to i64*
 or
  %a.0.loadme.cast.cast = bitcast i8 addrspace(100)* %loadme.cast to i64*
These should be:
  %a.0.storeme.cast.cast = bitcast i8 addrspace(100)* %storeme.cast to i64
addrspace(100)*
  %a.0.loadme.cast.cast = bitcast i8 addrspace(100)* %loadme.cast to i64
addrspace(100)*

-----------------------------------------


target datalayout =
"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128-p100:64:64:64"

declare void @llvm.memcpy.p0i8.p100i8.i64(i8* nocapture, i8 addrspace(100)*
nocapture, i64, i32, i1)
declare void @llvm.memcpy.p100i8.p0i8.i64(i8 addrspace(100)* nocapture, i8*
nocapture, i64, i32, i1)

define void @teststore(i64 addrspace(100)* %storeme) {
entry:
  %a = alloca i64
  store i64 7, i64 * %a
  %storeme.cast = bitcast i64 addrspace(100)* %storeme to i8 addrspace(100)*
  %a.cast = bitcast i64 * %a to i8 *
  call void @llvm.memcpy.p100i8.p0i8.i64(i8 addrspace(100)* %storeme.cast, i8*
%a.cast, i64 8, i32 1, i1 true)
  ret void
}


define i64 @testload(i64 addrspace(100)* %loadme) {
entry:
  %a = alloca i64
  %loadme.cast = bitcast i64 addrspace(100)* %loadme to i8 addrspace(100)*
  %a.cast = bitcast i64 * %a to i8 *
  call void @llvm.memcpy.p0i8.p100i8.i64(i8* %a.cast, i8 addrspace(100)*
%loadme.cast, i64 8, i32 1, i1 true)
  %ret = load i64 * %a
  ret i64 %ret
}




-----------------------------------------

I have also created a patch to SROA.cpp which causes assertion failures when
adding such bitcasts. I have not been able to find a fix but
the added assert gets triggered in line 2976 (getAdjustedPtr in
visitMemTransferInst).

Index: SROA.cpp
===================================================================
--- SROA.cpp    (revision 181030)
+++ SROA.cpp    (working copy)
@@ -1869,6 +1869,18 @@
                                   Indices);
 }

+// Check that we're not adding a bit-cast between address spaces.
+static Value *makeBitCast(IRBuilderTy &IRB, Value *V, Type *Ty, const Twine
&Name = "")
+{
+  if( V->getType()->isPointerTy() && Ty->isPointerTy() ) {
+    unsigned VAS = V->getType()->getPointerAddressSpace();
+    unsigned TyAS = Ty->getPointerAddressSpace();
+    assert( VAS == TyAS && "Pointer address spaces do not match!");
+  }
+  return IRB.CreateBitCast(V, Ty, Name);
+}
+
+
 /// \brief Compute an adjusted pointer from Ptr by Offset bytes where the
 /// resulting pointer has PointerTy.
 ///
@@ -1953,7 +1965,7 @@

   if (!OffsetPtr) {
     if (!Int8Ptr) {
-      Int8Ptr = IRB.CreateBitCast(Ptr, IRB.getInt8PtrTy(),
+      Int8Ptr = makeBitCast(IRB, Ptr, IRB.getInt8PtrTy(),
                                   "raw_cast");
       Int8PtrOffset = Offset;
     }
@@ -1966,7 +1978,7 @@

   // On the off chance we were targeting i8*, guard the bitcast here.
   if (Ptr->getType() != PointerTy)
-    Ptr = IRB.CreateBitCast(Ptr, PointerTy, "cast");
+    Ptr = makeBitCast(IRB, Ptr, PointerTy, "cast");

   return Ptr;
 }
@@ -2021,7 +2033,7 @@
   if (V->getType()->isPointerTy() && Ty->isIntegerTy())
     return IRB.CreatePtrToInt(V, Ty);

-  return IRB.CreateBitCast(V, Ty);
+  return makeBitCast(IRB, V, Ty);
 }

 /// \brief Test whether the given alloca partition can be promoted to a
vector.

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