Fix a bug in the 3-address conversion of LEA when one of the operands is an

undef virtual register. The problem is that ProcessImplicitDefs removes the
definition of the register and marks all uses as undef. If we lose the undef
marker then we get a register which has no def, is not marked as undef. The
live interval analysis does not collect information for these virtual
registers and we crash in later passes.

Together with Michael Kuperstein <michael.m.kuperstein@intel.com>

llvm-svn: 160260

2 files changed, 23 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index 9f5f66e37c8..8ba31945058 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -2016,6 +2016,13 @@ X86InstrInfo::convertToThreeAddress(MachineFunction::iterator &MFI,
                         .addReg(Dest, RegState::Define |
                                 getDeadRegState(isDead)),
                         Src, isKill, Src2, isKill2);
+
+      // Preserve undefness of the operands.
+      bool isUndef = MI->getOperand(1).isUndef();
+      bool isUndef2 = MI->getOperand(2).isUndef();
+      NewMI->getOperand(1).setIsUndef(isUndef);
+      NewMI->getOperand(3).setIsUndef(isUndef2);
+
       if (LV && isKill2)
         LV->replaceKillInstruction(Src2, MI, NewMI);
       break;
diff --git a/llvm/test/CodeGen/X86/2012-07-16-LeaUndef.ll b/llvm/test/CodeGen/X86/2012-07-16-LeaUndef.ll
new file mode 100644
index 00000000000..9e5cbd2f337
--- /dev/null
+++ b/llvm/test/CodeGen/X86/2012-07-16-LeaUndef.ll
@@ -0,0 +1,16 @@
+; RUN: llc < %s -march=x86-64 -mcpu=corei7
+
+define void @autogen_SD2543() {
+A:
+  %E83 = add i32 0, 1
+  %E820 = add i32 0, undef
+  br label %C
+C:
+  %B908 = add i32 %E83, %E820
+  store i32 %B908, i32* undef
+  %Sl2391 = select i1 undef, i32 undef, i32 %E83
+  %Cmp3114 = icmp ne i32 %Sl2391, undef
+  br i1 %Cmp3114, label %C, label %G
+G:
+  ret void
+}