From bde81d5be9bdc3837c77f8f3c63c013b6e4bbc8d Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Fri, 23 Sep 2011 22:41:57 +0000
Subject: [PATCH] PR10998: It is not legal to sink an instruction past the
 terminator of a block; make sure we don't do that.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140428 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/TwoAddressInstructionPass.cpp   | 10 ++++-
 test/CodeGen/X86/twoaddr-sink-terminator.ll | 43 +++++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/X86/twoaddr-sink-terminator.ll

diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index dfd258d592e..d8793782228 100644
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -177,6 +177,10 @@ char &llvm::TwoAddressInstructionPassID = TwoAddressInstructionPass::ID;
 bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB,
                                            MachineInstr *MI, unsigned SavedReg,
                                            MachineBasicBlock::iterator OldPos) {
+  // FIXME: Shouldn't we be trying to do this before we three-addressify the
+  // instruction?  After this transformation is done, we no longer need
+  // the instruction to be in three-address form.
+
   // Check if it's safe to move this instruction.
   bool SeenStore = true; // Be conservative.
   if (!MI->isSafeToMove(TII, AA, SeenStore))
@@ -217,7 +221,11 @@ bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB,
     break;
   }
 
-  if (!KillMI || KillMI->getParent() != MBB || KillMI == MI)
+  // If we find the instruction that kills SavedReg, and it is in an
+  // appropriate location, we can try to sink the current instruction
+  // past it.
+  if (!KillMI || KillMI->getParent() != MBB || KillMI == MI ||
+      KillMI->getDesc().isTerminator())
     return false;
 
   // If any of the definitions are used by another instruction between the
diff --git a/test/CodeGen/X86/twoaddr-sink-terminator.ll b/test/CodeGen/X86/twoaddr-sink-terminator.ll
new file mode 100644
index 00000000000..209d474a074
--- /dev/null
+++ b/test/CodeGen/X86/twoaddr-sink-terminator.ll
@@ -0,0 +1,43 @@
+; RUN: llc < %s -verify-coalescing
+; PR10998
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
+target triple = "i386-unknown-freebsd8.2"
+
+define void @test(i32 %arg1) nounwind align 2 {
+bb11:
+  %tmp13 = and i32 %arg1, 7
+  %tmp14 = add i32 %tmp13, -5
+  switch i32 %tmp13, label %bb18 [
+    i32 0, label %bb21
+    i32 4, label %bb22
+    i32 3, label %bb21
+    i32 2, label %bb19
+  ]
+
+bb18:
+  %tmp202 = call i32 @f() nounwind
+  unreachable
+
+bb19:
+  %tmp20 = call i32 @f() nounwind
+  br label %bb24
+
+bb21:
+  %tmp203 = call i32 @f() nounwind
+  br label %bb24
+
+bb22:
+  %tmp23 = call i32 @f() nounwind
+  br label %bb24
+
+bb24:
+  %tmp15 = icmp ult i32 %tmp14, 2
+  %tmp55 = select i1 %tmp15, i32 45, i32 44
+  %tmp56 = call i32 @f2(i32 %tmp55)
+  unreachable
+}
+
+declare i32 @f()
+
+declare i32 @f2(i32)