Fix the root cause of PR15348 by correctly handling alignment 0 on

memory intrinsics in the SDAG builder.

When alignment is zero, the lang ref says that *no* alignment
assumptions can be made. This is the exact opposite of the internal API
contracts of the DAG where alignment 0 indicates that the alignment can
be made to be anything desired.

There is another, more explicit alignment that is better suited for the
role of "no alignment at all": an alignment of 1. Map the intrinsic
alignment to this early so that we don't end up generating aligned DAGs.

It is really terrifying that we've never seen this before, but we
suddenly started generating a large number of alignment 0 memcpys due to
the new code to do memcpy-based copying of POD class members. That patch
contains a bug that rounds bitfield alignments down when they are the
first field. This can in turn produce zero alignments.

This fixes weird crashes I've seen in library users of LLVM on 32-bit
hosts, etc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176022 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 0640311a77b4358364df7384e151f10a95f5862f..81b0ea7e7bc23191fc135c028fb512c88e18ddcd 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -3867,6 +3867,7 @@ SDValue SelectionDAG::getMemcpy(SDValue Chain, DebugLoc dl, SDValue Dst,
                                 unsigned Align, bool isVol, bool AlwaysInline,
                                 MachinePointerInfo DstPtrInfo,
                                 MachinePointerInfo SrcPtrInfo) {
+  assert(Align && "The SDAG layer expects explicit alignment and reservers 0");
 
   // Check to see if we should lower the memcpy to loads and stores first.
   // For cases within the target-specified limits, this is the best choice.
@@ -3934,6 +3935,7 @@ SDValue SelectionDAG::getMemmove(SDValue Chain, DebugLoc dl, SDValue Dst,
                                  unsigned Align, bool isVol,
                                  MachinePointerInfo DstPtrInfo,
                                  MachinePointerInfo SrcPtrInfo) {
+  assert(Align && "The SDAG layer expects explicit alignment and reservers 0");
 
   // Check to see if we should lower the memmove to loads and stores first.
   // For cases within the target-specified limits, this is the best choice.
@@ -3988,6 +3990,7 @@ SDValue SelectionDAG::getMemset(SDValue Chain, DebugLoc dl, SDValue Dst,
                                 SDValue Src, SDValue Size,
                                 unsigned Align, bool isVol,
                                 MachinePointerInfo DstPtrInfo) {
+  assert(Align && "The SDAG layer expects explicit alignment and reservers 0");
 
   // Check to see if we should lower the memset to stores first.
   // For cases within the target-specified limits, this is the best choice.

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 3a5569614cdef92cbe41a7f00c3f31f465b89983..3a6f9b23c790d8a01820f2cf5a8672ba665b216e 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4467,6 +4467,8 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     SDValue Op2 = getValue(I.getArgOperand(1));
     SDValue Op3 = getValue(I.getArgOperand(2));
     unsigned Align = cast<ConstantInt>(I.getArgOperand(3))->getZExtValue();
+    if (!Align)
+      Align = 1; // @llvm.memcpy defines 0 and 1 to both mean no alignment.
     bool isVol = cast<ConstantInt>(I.getArgOperand(4))->getZExtValue();
     DAG.setRoot(DAG.getMemcpy(getRoot(), dl, Op1, Op2, Op3, Align, isVol, false,
                               MachinePointerInfo(I.getArgOperand(0)),
@@ -4483,6 +4485,8 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     SDValue Op2 = getValue(I.getArgOperand(1));
     SDValue Op3 = getValue(I.getArgOperand(2));
     unsigned Align = cast<ConstantInt>(I.getArgOperand(3))->getZExtValue();
+    if (!Align)
+      Align = 1; // @llvm.memset defines 0 and 1 to both mean no alignment.
     bool isVol = cast<ConstantInt>(I.getArgOperand(4))->getZExtValue();
     DAG.setRoot(DAG.getMemset(getRoot(), dl, Op1, Op2, Op3, Align, isVol,
                               MachinePointerInfo(I.getArgOperand(0))));
@@ -4500,6 +4504,8 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     SDValue Op2 = getValue(I.getArgOperand(1));
     SDValue Op3 = getValue(I.getArgOperand(2));
     unsigned Align = cast<ConstantInt>(I.getArgOperand(3))->getZExtValue();
+    if (!Align)
+      Align = 1; // @llvm.memmove defines 0 and 1 to both mean no alignment.
     bool isVol = cast<ConstantInt>(I.getArgOperand(4))->getZExtValue();
     DAG.setRoot(DAG.getMemmove(getRoot(), dl, Op1, Op2, Op3, Align, isVol,
                                MachinePointerInfo(I.getArgOperand(0)),

diff --git a/test/CodeGen/X86/memcpy.ll b/test/CodeGen/X86/memcpy.ll
index 2e02e45c8ddfee9e41e09291756d9cc8e6e3c64a..3372a4adc5eeb5135a3c7e6fac5892e2a136f8f5 100644 (file)
--- a/test/CodeGen/X86/memcpy.ll
+++ b/test/CodeGen/X86/memcpy.ll
@@ -105,3 +105,16 @@ entry:
   ret void
 }
 
+define void @PR15348(i8* %a, i8* %b) {
+; Ensure that alignment of '0' in an @llvm.memcpy intrinsic results in
+; unaligned loads and stores.
+; LINUX: PR15348
+; LINUX: movb
+; LINUX: movb
+; LINUX: movq
+; LINUX: movq
+; LINUX: movq
+; LINUX: movq
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %a, i8* %b, i64 17, i32 0, i1 false)
+  ret void
+}

diff --git a/test/CodeGen/X86/memset.ll b/test/CodeGen/X86/memset.ll
index b35f2615d0f694f5016fce5b636e9e07aadfb4f9..0d479f0abe7b98ed58de9ca25408e0ed6d0f9b57 100644 (file)
--- a/test/CodeGen/X86/memset.ll
+++ b/test/CodeGen/X86/memset.ll
@@ -20,15 +20,18 @@ entry:
 ; X86: movl $0,
 ; X86: movl $0,
 ; X86-NOT: movl $0,
+; X86: ret
 
 ; XMM: xorps %xmm{{[0-9]+}}, [[Z:%xmm[0-9]+]]
 ; XMM: movaps [[Z]],
 ; XMM: movaps [[Z]],
 ; XMM-NOT: movaps
+; XMM: ret
 
 ; YMM: vxorps %ymm{{[0-9]+}}, %ymm{{[0-9]+}}, [[Z:%ymm[0-9]+]]
 ; YMM: vmovaps [[Z]],
 ; YMM-NOT: movaps
+; YMM: ret
 
        call void @foo( %struct.x* %up_mvd116 ) nounwind 
        ret void
@@ -37,3 +40,16 @@ entry:
 declare void @foo(%struct.x*)
 
 declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
+
+define void @PR15348(i8* %a) {
+; Ensure that alignment of '0' in an @llvm.memset intrinsic results in
+; unaligned loads and stores.
+; XMM: PR15348
+; XMM: movb $0,
+; XMM: movl $0,
+; XMM: movl $0,
+; XMM: movl $0,
+; XMM: movl $0,
+  call void @llvm.memset.p0i8.i64(i8* %a, i8 0, i64 17, i32 0, i1 false)
+  ret void
+}