[llvm] r308267 - [X86] Prevent an assertion failure if a gather intrinsic is passed a non-constant scale value.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Mon Jul 17 23:49:23 2017
New Revision: 308267

URL: http://llvm.org/viewvc/llvm-project?rev=308267&view=rev
Log:
[X86] Prevent an assertion failure if a gather intrinsic is passed a non-constant scale value.

This isn't legal code, but we shouldn't crash on it. Now we just don't convert the gather intrinsic if the scale isn't constant and let it go through to isel where we'll report an isel failure.

Fixes PR33772.

Added:
    llvm/trunk/test/CodeGen/X86/pr33772.ll
Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=308267&r1=308266&r2=308267&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Mon Jul 17 23:49:23 2017
@@ -20195,7 +20195,10 @@ static SDValue getAVX2GatherNode(unsigne
                                  SDValue Index, SDValue ScaleOp, SDValue Chain,
                                  const X86Subtarget &Subtarget) {
   SDLoc dl(Op);
-  auto *C = cast<ConstantSDNode>(ScaleOp);
+  auto *C = dyn_cast<ConstantSDNode>(ScaleOp);
+  // Scale must be constant.
+  if (!C)
+    return SDValue();
   SDValue Scale = DAG.getTargetConstant(C->getZExtValue(), dl, MVT::i8);
   EVT MaskVT = Mask.getValueType();
   SDVTList VTs = DAG.getVTList(Op.getValueType(), MaskVT, MVT::Other);
@@ -20217,7 +20220,10 @@ static SDValue getGatherNode(unsigned Op
                               SDValue Index, SDValue ScaleOp, SDValue Chain,
                               const X86Subtarget &Subtarget) {
   SDLoc dl(Op);
-  auto *C = cast<ConstantSDNode>(ScaleOp);
+  auto *C = dyn_cast<ConstantSDNode>(ScaleOp);
+  // Scale must be constant.
+  if (!C)
+    return SDValue();
   SDValue Scale = DAG.getTargetConstant(C->getZExtValue(), dl, MVT::i8);
   MVT MaskVT = MVT::getVectorVT(MVT::i1,
                              Index.getSimpleValueType().getVectorNumElements());
@@ -20242,7 +20248,10 @@ static SDValue getScatterNode(unsigned O
                                SDValue Index, SDValue ScaleOp, SDValue Chain,
                                const X86Subtarget &Subtarget) {
   SDLoc dl(Op);
-  auto *C = cast<ConstantSDNode>(ScaleOp);
+  auto *C = dyn_cast<ConstantSDNode>(ScaleOp);
+  // Scale must be constant.
+  if (!C)
+    return SDValue();
   SDValue Scale = DAG.getTargetConstant(C->getZExtValue(), dl, MVT::i8);
   SDValue Disp = DAG.getTargetConstant(0, dl, MVT::i32);
   SDValue Segment = DAG.getRegister(0, MVT::i32);
@@ -20261,7 +20270,10 @@ static SDValue getPrefetchNode(unsigned
                                SDValue ScaleOp, SDValue Chain,
                                const X86Subtarget &Subtarget) {
   SDLoc dl(Op);
-  auto *C = cast<ConstantSDNode>(ScaleOp);
+  auto *C = dyn_cast<ConstantSDNode>(ScaleOp);
+  // Scale must be constant.
+  if (!C)
+    return SDValue();
   SDValue Scale = DAG.getTargetConstant(C->getZExtValue(), dl, MVT::i8);
   SDValue Disp = DAG.getTargetConstant(0, dl, MVT::i32);
   SDValue Segment = DAG.getRegister(0, MVT::i32);

Added: llvm/trunk/test/CodeGen/X86/pr33772.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr33772.ll?rev=308267&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/pr33772.ll (added)
+++ llvm/trunk/test/CodeGen/X86/pr33772.ll Mon Jul 17 23:49:23 2017
@@ -0,0 +1,13 @@
+; RUN: not llc < %s -mcpu=skylake-avx512 2>&1 | FileCheck %s
+
+; make sure we don't crash if scale for gather isn't constant.
+
+; CHECK: LLVM ERROR: Cannot select: intrinsic %llvm.x86.avx512.gather.dpi.512
+declare <16 x i32> @llvm.x86.avx512.gather.dpi.512(<16 x i32>, i8*, <16 x i32>, i16, i32)
+
+define internal <16 x i32> @__gather_base_offsets32_i32(i8* readonly %ptr, i32 %offset_scale, <16 x i32> %offsets, <16 x i8> %vecmask) {
+  %mask_vec_i1.i.i = icmp ne <16 x i8> %vecmask, zeroinitializer
+  %mask_i16.i = bitcast <16 x i1> %mask_vec_i1.i.i to i16
+  %res = tail call <16 x i32> @llvm.x86.avx512.gather.dpi.512(<16 x i32> undef, i8* %ptr, <16 x i32> %offsets, i16 %mask_i16.i, i32 %offset_scale)
+  ret <16 x i32> %res
+}