From 56b68851046ab8388fa9d54e2f5f8339cb7b7f63 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Mon, 13 Oct 2008 20:52:04 +0000
Subject: [PATCH] When doing the very-late shift-and address-mode optimization,
 create a new DAG node to represent the new shift to keep the DAG consistent,
 even though it'll almost always be folded into the address.

If a user of the resulting address has multiple uses, the
nodes may get revisited by a later MatchAddress call, in which
case DAG inconsistencies do matter.

This fixes PR2849.

llvm-svn: 57465
---
 llvm/lib/Target/X86/X86ISelDAGToDAG.cpp |  3 ++
 llvm/test/CodeGen/X86/pr2849.ll         | 38 +++++++++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 llvm/test/CodeGen/X86/pr2849.ll

diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 50c8f5b8708f..b0134152ffb1 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -989,8 +989,11 @@ DOUT << "AlreadySelected " << AlreadySelected << "\n";
                                            SDValue(C2, 0), SDValue(C1, 0));
     SDValue NewAND = CurDAG->getNode(ISD::AND, N.getValueType(),
                                        Shift.getOperand(0), NewANDMask);
+    SDValue NewSHIFT = CurDAG->getNode(ISD::SHL, N.getValueType(),
+                                       NewAND, SDValue(C1, 0));
     NewANDMask.getNode()->setNodeId(Shift.getNode()->getNodeId());
     NewAND.getNode()->setNodeId(N.getNode()->getNodeId());
+    CurDAG->ReplaceAllUsesWith(N, NewSHIFT);
     
     AM.Scale = 1 << ShiftCst;
     AM.IndexReg = NewAND;
diff --git a/llvm/test/CodeGen/X86/pr2849.ll b/llvm/test/CodeGen/X86/pr2849.ll
new file mode 100644
index 000000000000..673598fe7249
--- /dev/null
+++ b/llvm/test/CodeGen/X86/pr2849.ll
@@ -0,0 +1,38 @@
+; RUN: llvm-as < %s | llc
+; PR2849
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
+target triple = "x86_64-unknown-linux-gnu"
+	%struct.BaseBoundPtrs = type { i8*, i8* }
+	%struct.HashEntry = type { %struct.BaseBoundPtrs }
+	%struct.NODE = type { i8, i8, %struct.anon }
+	%struct.anon = type { %struct.xlist }
+	%struct.xlist = type { %struct.NODE*, %struct.NODE* }
+	%struct.xvect = type { %struct.NODE** }
+@hash_table_begin = external global %struct.HashEntry*
+
+define void @obshow() {
+entry:
+	%tmp = load %struct.HashEntry** @hash_table_begin, align 8
+	br i1 false, label %xlygetvalue.exit, label %xlygetvalue.exit
+
+xlygetvalue.exit:
+	%storemerge.in.i = phi %struct.NODE** [ null, %entry ], [ null, %entry ]
+	%storemerge.i = load %struct.NODE** %storemerge.in.i
+	%tmp1 = ptrtoint %struct.NODE** %storemerge.in.i to i64
+	%tmp2 = lshr i64 %tmp1, 3
+	%tmp3 = and i64 %tmp2, 2147483647
+	%tmp4 = getelementptr %struct.HashEntry* %tmp, i64 %tmp3, i32 0, i32 1
+	%tmp7 = load i8** %tmp4, align 8
+	%tmp8 = getelementptr %struct.NODE* %storemerge.i, i64 0, i32 2
+	%tmp9 = bitcast %struct.anon* %tmp8 to %struct.NODE***
+	%tmp11 = load %struct.NODE*** %tmp9, align 8
+	%tmp12 = ptrtoint %struct.NODE** %tmp11 to i64
+	%tmp13 = lshr i64 %tmp12, 3
+	%tmp14 = and i64 %tmp13, 2147483647
+	%tmp15 = getelementptr %struct.HashEntry* %tmp, i64 %tmp14, i32 0, i32 1
+	call fastcc void @xlprint(i8** %tmp4, i8* %tmp7, i8** %tmp15)
+	ret void
+}
+
+declare fastcc void @xlprint(i8**, i8*, i8**)