Remove handling of AddrSpaceCast in stripAndAccumulateInBoundsConstantOffsets

[simoncook]

Summary

Unlike BitCasts, AddrSpaceCasts do not always produce an output the same size as its input, which was previously assumed. This fixes cases where two address spaces do not have the same size pointer, as an assertion failure would occur in LoopSimplify when an the output of an AddrSpaceCast is used as an input operand for a GEP as the base pointer would be of a different size to an offset.

[reames]

LGTM w/minor comment addressed.

test/Transforms/LoopUnswitch/2015-09-18-Addrspace.ll

2 ↗

(On Diff #35221)

A comment about what this is testing a FileCheck directive or two would be good.

[simoncook]

Added comment to test as per recommendation.

As I do not yet have commit access, could someone commit this on my behalf?

llvm/trunk/lib/IR/Value.cpp

do {
     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
       if (!GEP->isInBounds())
         return V;
       APInt GEPOffset(Offset);
       if (!GEP->accumulateConstantOffset(DL, GEPOffset))
         return V;
       Offset = GEPOffset;
       V = GEP->getPointerOperand();
-    } else if (Operator::getOpcode(V) == Instruction::BitCast ||
-               Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
+    } else if (Operator::getOpcode(V) == Instruction::BitCast) {
       V = cast<Operator>(V)->getOperand(0);
     } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
       V = GA->getAliasee();
     } else {
       return V;
     }
     assert(V->getType()->isPointerTy() && "Unexpected operand type!");
   } while (Visited.insert(V).second);

llvm/trunk/test/Transforms/LoopUnswitch/2015-09-18-Addrspace.ll

+; RUN: opt < %s -loop-unswitch -S | FileCheck %s
+
+; In cases where two address spaces do not have the same size pointer, the
+; input for the addrspacecast should not be used as a substitute for itself
+; when manipulating the pointer.
+
+target datalayout = "e-m:e-p:16:16-p1:32:16-i32:16-i64:16-n8:16"
+
+define void @foo() {
+; CHECK-LABEL: @foo
+entry:
+  %arrayidx.i1 = getelementptr inbounds i16, i16* undef, i16 undef
+  %arrayidx.i = addrspacecast i16* %arrayidx.i1 to i16 addrspace(1)*
+  br i1 undef, label %for.body.i, label %bar.exit
+
+for.body.i:                                       ; preds = %for.body.i, %entry
+; When we call makeLoopInvariant (i.e. trivial LICM) on this load, it 
+; will try to find the base object to prove deferenceability.  If we look
+; through the addrspacecast, we'll fail an assertion about bitwidths matching
+; CHECK-LABEL: for.body.i
+; CHECK:   %0 = load i16, i16 addrspace(1)* %arrayidx.i, align 2
+  %0 = load i16, i16 addrspace(1)* %arrayidx.i, align 2
+  %cmp1.i = icmp eq i16 %0, 0
+  br i1 %cmp1.i, label %bar.exit, label %for.body.i
+
+bar.exit:                                         ; preds = %for.body.i, %entry
+  ret void
+}