Handle REG_SEQUENCE with implicitly defined operands.

Code like that would only be produced by bugpoint, but we should still
handle it correctly.

When a register is defined by a REG_SEQUENCE of undefs, the register
itself is undef. Previously, we would create a register with uses but no
defs.

Fixes part of PR10520.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136401 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 27 insertions, 0 deletions

diff --git a/lib/CodeGen/ProcessImplicitDefs.cpp b/lib/CodeGen/ProcessImplicitDefs.cpp
index c04d65637c..b1d8c97602 100644
--- a/lib/CodeGen/ProcessImplicitDefs.cpp
+++ b/lib/CodeGen/ProcessImplicitDefs.cpp
@@ -125,8 +125,14 @@ bool ProcessImplicitDefs::runOnMachineFunction(MachineFunction &fn) {
             LiveVariables::VarInfo& vi = LV->getVarInfo(MO.getReg());
             vi.removeKill(MI);
           }
+          unsigned Reg = MI->getOperand(0).getReg();
           MI->eraseFromParent();
           Changed = true;
+
+          // A REG_SEQUENCE may have been expanded into partial definitions.
+          // If this was the last one, mark Reg as implicitly defined.
+          if (TargetRegisterInfo::isVirtualRegister(Reg) && MRI->def_empty(Reg))
+            ImpDefRegs.insert(Reg);
           continue;
         }
       }
diff --git a/test/CodeGen/ARM/crash.ll b/test/CodeGen/ARM/crash.ll
index 4b6876df4a..5ecfe15511 100644
--- a/test/CodeGen/ARM/crash.ll
+++ b/test/CodeGen/ARM/crash.ll
@@ -27,3 +27,24 @@ bb3:
 exit:
   ret void
 }
+
+; PR10520 - REG_SEQUENCE with implicit-def operands.
+define arm_aapcs_vfpcc void @foo() nounwind align 2 {
+bb:
+  %tmp = shufflevector <2 x i64> undef, <2 x i64> undef, <1 x i32> <i32 1>
+  %tmp8 = bitcast <1 x i64> %tmp to <2 x float>
+  %tmp9 = shufflevector <2 x float> %tmp8, <2 x float> %tmp8, <4 x i32> <i32 1, i32 1, i32 1, i32 1>
+  %tmp10 = fmul <4 x float> undef, %tmp9
+  %tmp11 = fadd <4 x float> %tmp10, undef
+  %tmp12 = fadd <4 x float> undef, %tmp11
+  %tmp13 = bitcast <4 x float> %tmp12 to i128
+  %tmp14 = bitcast i128 %tmp13 to <4 x float>
+  %tmp15 = bitcast <4 x float> %tmp14 to i128
+  %tmp16 = bitcast i128 %tmp15 to <4 x float>
+  %tmp17 = bitcast <4 x float> %tmp16 to i128
+  %tmp18 = bitcast i128 %tmp17 to <4 x float>
+  %tmp19 = bitcast <4 x float> %tmp18 to i128
+  %tmp20 = bitcast i128 %tmp19 to <4 x float>
+  store <4 x float> %tmp20, <4 x float>* undef, align 16
+  ret void
+}