From: Tom Stellard <thomas.stellard@amd.com>
Date: Fri, 7 Oct 2016 14:23:29 +0000 (+0000)
Subject: [ValueTracking] Fix crash in GetPointerBaseWithConstantOffset()
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=8b2bb5de9ac189d7cbff302b4cdab8eb492b4bb4;p=llvm

[ValueTracking] Fix crash in GetPointerBaseWithConstantOffset()

Summary:
While walking defs of pointer operands we were assuming that the pointer
size would remain constant.  This is not true, because addresspacecast
instructions may cast the pointer to an address space with a different
pointer width.

This partial reverts r282612, which was a more conservative solution
to this problem.

Reviewers: reames, sanjoy, apilipenko

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D24772

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283557 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 64a900d2960..6a4aaf1727a 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -2855,21 +2855,22 @@ Value *llvm::GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
       break;
 
     if (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
-      APInt GEPOffset(BitWidth, 0);
+      // If one of the values we have visited is an addrspacecast, then
+      // the pointer type of this GEP may be different from the type
+      // of the Ptr parameter which was passed to this function.  This
+      // means when we construct GEPOffset, we need to use the size
+      // of GEP's pointer type rather than the size of the original
+      // pointer type.
+      APInt GEPOffset(DL.getPointerTypeSizeInBits(Ptr->getType()), 0);
       if (!GEP->accumulateConstantOffset(DL, GEPOffset))
         break;
 
-      ByteOffset += GEPOffset;
+      ByteOffset += GEPOffset.getSExtValue();
 
       Ptr = GEP->getPointerOperand();
-    } else if (Operator::getOpcode(Ptr) == Instruction::BitCast) {
+    } else if (Operator::getOpcode(Ptr) == Instruction::BitCast ||
+               Operator::getOpcode(Ptr) == Instruction::AddrSpaceCast) {
       Ptr = cast<Operator>(Ptr)->getOperand(0);
-    } else if (AddrSpaceCastInst *ASCI = dyn_cast<AddrSpaceCastInst>(Ptr)) {
-      Value *SourcePtr = ASCI->getPointerOperand();
-      // Don't look through addrspace cast which changes pointer size
-      if (BitWidth != DL.getPointerTypeSizeInBits(SourcePtr->getType()))
-        break;
-      Ptr = SourcePtr;
     } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
       if (GA->isInterposable())
         break;
diff --git a/test/Analysis/ValueTracking/get-pointer-base-with-const-off.ll b/test/Analysis/ValueTracking/get-pointer-base-with-const-off.ll
new file mode 100644
index 00000000000..6752b08f000
--- /dev/null
+++ b/test/Analysis/ValueTracking/get-pointer-base-with-const-off.ll
@@ -0,0 +1,26 @@
+; RUN: opt -gvn -S < %s | FileCheck %s
+
+; Make sure we don't crash when analyzing an addrspacecast in
+; GetPointerBaseWithConstantOffset()
+
+target datalayout = "e-p:32:32-p4:64:64"
+
+define i32 @addrspacecast-crash() {
+; CHECK-LABEL: @addrspacecast-crash
+; CHECK: %tmp = alloca [25 x i64]
+; CHECK: %tmp1 = getelementptr inbounds [25 x i64], [25 x i64]* %tmp, i32 0, i32 0
+; CHECK: %tmp2 = addrspacecast i64* %tmp1 to <8 x i64> addrspace(4)*
+; CHECK: store <8 x i64> zeroinitializer, <8 x i64> addrspace(4)* %tmp2
+; CHECK-NOT: load
+bb:
+  %tmp = alloca [25 x i64]
+  %tmp1 = getelementptr inbounds [25 x i64], [25 x i64]* %tmp, i32 0, i32 0
+  %tmp2 = addrspacecast i64* %tmp1 to <8 x i64> addrspace(4)*
+  %tmp3 = getelementptr inbounds <8 x i64>, <8 x i64> addrspace(4)* %tmp2, i64 0
+  store <8 x i64> zeroinitializer, <8 x i64> addrspace(4)* %tmp3
+  %tmp4 = getelementptr inbounds [25 x i64], [25 x i64]* %tmp, i32 0, i32 0
+  %tmp5 = addrspacecast i64* %tmp4 to i32 addrspace(4)*
+  %tmp6 = getelementptr inbounds i32, i32 addrspace(4)* %tmp5, i64 10
+  %tmp7 = load i32, i32 addrspace(4)* %tmp6, align 4
+  ret i32 %tmp7
+}
diff --git a/test/Transforms/GVN/addrspace-cast.ll b/test/Transforms/GVN/addrspace-cast.ll
deleted file mode 100644
index 9a479fc65ac..00000000000
--- a/test/Transforms/GVN/addrspace-cast.ll
+++ /dev/null
@@ -1,21 +0,0 @@
-; RUN: opt < %s -gvn -S | FileCheck %s
-target datalayout = "e-m:e-p:16:16-p1:32:16-i32:16-i64:16-n8:16"
-
-; 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.
-
-; Check that we don't hit the assert in this scenario
-define i8 @test(i32 %V, i32* %P) {
-; CHECK-LABEL: @test(
-; CHECK: load
-  %P1 = getelementptr inbounds i32, i32* %P, i16 16
-
-  store i32 %V, i32* %P1
-
-  %P2 = addrspacecast i32* %P1 to i8 addrspace(1)*
-  %P3 = getelementptr i8, i8 addrspace(1)* %P2, i32 2
-
-  %A = load i8, i8 addrspace(1)* %P3
-  ret i8 %A
-}