[llvm] r267420 - [PR27390] [CodeGen] Reject indexed loads in CombinerDAG.

[Marcin Koscielnicki via llvm-commits]

Author: koriakin
Date: Mon Apr 25 10:43:44 2016
New Revision: 267420

URL: http://llvm.org/viewvc/llvm-project?rev=267420&view=rev
Log:
[PR27390] [CodeGen] Reject indexed loads in CombinerDAG.

visitAND, when folding and (load) forgets to check which output of
an indexed load is involved, happily folding the updated address
output on the following testcase:

target datalayout = "e-m:e-i64:64-n32:64"
target triple = "powerpc64le-unknown-linux-gnu"

%typ = type { i32, i32 }

define signext i32 @_Z8access_pP1Tc(%typ* %p, i8 zeroext %type) {
  %b = getelementptr inbounds %typ, %typ* %p, i64 0, i32 1
  %1 = load i32, i32* %b, align 4
  %2 = ptrtoint i32* %b to i64
  %3 = and i64 %2, -35184372088833
  %4 = inttoptr i64 %3 to i32*
  %_msld = load i32, i32* %4, align 4
  %zzz = add i32 %1,  %_msld
  ret i32 %zzz
}

Fix this by checking ResNo.

I've found a few more places that currently neglect to check for
indexed load, and tightened them up as well, but I don't have test
cases for them.  In fact, they might not be triggerable at all,
at least with current targets.  Still, better safe than sorry.

Differential Revision: http://reviews.llvm.org/D19202

Added:
    llvm/trunk/test/CodeGen/PowerPC/2016-04-17-combine.ll
Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=267420&r1=267419&r2=267420&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Mon Apr 25 10:43:44 2016
@@ -963,7 +963,8 @@ void DAGCombiner::ReplaceLoadWithPromote
 SDValue DAGCombiner::PromoteOperand(SDValue Op, EVT PVT, bool &Replace) {
   Replace = false;
   SDLoc dl(Op);
-  if (LoadSDNode *LD = dyn_cast<LoadSDNode>(Op)) {
+  if (ISD::isUNINDEXEDLoad(Op.getNode())) {
+    LoadSDNode *LD = cast<LoadSDNode>(Op);
     EVT MemVT = LD->getMemoryVT();
     ISD::LoadExtType ExtType = ISD::isNON_EXTLoad(LD)
       ? (TLI.isLoadExtLegal(ISD::ZEXTLOAD, PVT, MemVT) ? ISD::ZEXTLOAD
@@ -1167,6 +1168,9 @@ bool DAGCombiner::PromoteLoad(SDValue Op
   if (!LegalOperations)
     return false;
 
+  if (!ISD::isUNINDEXEDLoad(Op.getNode()))
+    return false;
+
   EVT VT = Op.getValueType();
   if (VT.isVector() || !VT.isInteger())
     return false;
@@ -3140,8 +3144,9 @@ SDValue DAGCombiner::visitAND(SDNode *N)
   // more cases.
   if ((N0.getOpcode() == ISD::EXTRACT_VECTOR_ELT &&
        N0.getValueSizeInBits() == N0.getOperand(0).getScalarValueSizeInBits() &&
-       N0.getOperand(0).getOpcode() == ISD::LOAD) ||
-      N0.getOpcode() == ISD::LOAD) {
+       N0.getOperand(0).getOpcode() == ISD::LOAD &&
+       N0.getOperand(0).getResNo() == 0) ||
+      (N0.getOpcode() == ISD::LOAD && N0.getResNo() == 0)) {
     LoadSDNode *Load = cast<LoadSDNode>( (N0.getOpcode() == ISD::LOAD) ?
                                          N0 : N0.getOperand(0) );
 

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=267420&r1=267419&r2=267420&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Mon Apr 25 10:43:44 2016
@@ -6961,6 +6961,8 @@ bool SelectionDAG::areNonVolatileConsecu
                                                   int Dist) const {
   if (LD->isVolatile() || Base->isVolatile())
     return false;
+  if (LD->isIndexed() || Base->isIndexed())
+    return false;
   if (LD->getChain() != Base->getChain())
     return false;
   EVT VT = LD->getValueType(0);

Added: llvm/trunk/test/CodeGen/PowerPC/2016-04-17-combine.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/2016-04-17-combine.ll?rev=267420&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/2016-04-17-combine.ll (added)
+++ llvm/trunk/test/CodeGen/PowerPC/2016-04-17-combine.ll Mon Apr 25 10:43:44 2016
@@ -0,0 +1,26 @@
+; RUN: llc <%s | FileCheck %s
+target datalayout = "e-m:e-i64:64-n32:64"
+target triple = "powerpc64le-unknown-linux-gnu"
+
+; PR27390 crasher
+
+%typ = type { i32, i32 }
+
+; On release builds, it doesn't crash, spewing nonsense instead.
+; To make sure it works, check that and is still alive.
+; CHECK: and
+; Also, in release, it emits a COPY from a 32-bit register to
+; a 64-bit register, which happens to be emitted as cror [!]
+; by the confused CodeGen.  Just to be sure, check there isn't one.
+; CHECK-NOT: cror
+; Function Attrs: uwtable
+define signext i32 @_Z8access_pP1Tc(%typ* %p, i8 zeroext %type) {
+  %b = getelementptr inbounds %typ, %typ* %p, i64 0, i32 1
+  %1 = load i32, i32* %b, align 4
+  %2 = ptrtoint i32* %b to i64
+  %3 = and i64 %2, -35184372088833
+  %4 = inttoptr i64 %3 to i32*
+  %_msld = load i32, i32* %4, align 4
+  %zzz = add i32 %1,  %_msld
+  ret i32 %zzz
+}