Don't glue users to extract_subreg when selecting the llvm.arm.ldrexd

intrinsic - it can cause impossible-to-schedule subgraphs to be
introduced.

PR15053.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176777 91177308-0d34-0410-b5e6-96231b3b80d8

Author: lhames

lib/Target/ARM/ARMISelDAGToDAG.cpp

@@ -3155,17 +3155,16 @@ SDNode *ARMDAGToDAGISel::Select(SDNode *N) {
       cast<MachineSDNode>(Ld)->setMemRefs(MemOp, MemOp + 1);
 
       // Remap uses.
-      SDValue Glue = isThumb ? SDValue(Ld, 2) : SDValue(Ld, 1);
+      SDValue OutChain = isThumb ? SDValue(Ld, 2) : SDValue(Ld, 1);
       if (!SDValue(N, 0).use_empty()) {
         SDValue Result;
         if (isThumb)
           Result = SDValue(Ld, 0);
         else {
           SDValue SubRegIdx = CurDAG->getTargetConstant(ARM::gsub_0, MVT::i32);
           SDNode *ResNode = CurDAG->getMachineNode(TargetOpcode::EXTRACT_SUBREG,
-              dl, MVT::i32, MVT::Glue, SDValue(Ld, 0), SubRegIdx, Glue);
+              dl, MVT::i32, SDValue(Ld, 0), SubRegIdx);
           Result = SDValue(ResNode,0);
-          Glue = Result.getValue(1);
         }
         ReplaceUses(SDValue(N, 0), Result);
       }
@@ -3176,13 +3175,12 @@ SDNode *ARMDAGToDAGISel::Select(SDNode *N) {
         else {
           SDValue SubRegIdx = CurDAG->getTargetConstant(ARM::gsub_1, MVT::i32);
           SDNode *ResNode = CurDAG->getMachineNode(TargetOpcode::EXTRACT_SUBREG,
-              dl, MVT::i32, MVT::Glue, SDValue(Ld, 0), SubRegIdx, Glue);
+              dl, MVT::i32, SDValue(Ld, 0), SubRegIdx);
           Result = SDValue(ResNode,0);
-          Glue = Result.getValue(1);
         }
         ReplaceUses(SDValue(N, 1), Result);
       }
-      ReplaceUses(SDValue(N, 2), Glue);
+      ReplaceUses(SDValue(N, 2), OutChain);
       return NULL;
     }
 

test/CodeGen/ARM/2013-03-09-PR15053.ll

@@ -0,0 +1,13 @@
+; RUN: llc -mtriple=armv7 < %s
+; PR15053
+
+declare i32 @llvm.arm.strexd(i32, i32, i8*) nounwind
+declare { i32, i32 } @llvm.arm.ldrexd(i8*) nounwind readonly
+
+define void @foo() {
+entry:
+  %0 = tail call { i32, i32 } @llvm.arm.ldrexd(i8* undef) nounwind
+  %1 = extractvalue { i32, i32 } %0, 0
+  %2 = tail call i32 @llvm.arm.strexd(i32 %1, i32 undef, i8* undef) nounwind
+  ret void
+}