Fix PR 18369: [Thumbv8] asserts due to inconsistent CPSR liveness of IT blocks

The issue is caused when Post-RA scheduler reorders a bundle instruction
(IT block). However, it only flips the CPSR liveness of the bundle instruction,
leaves the instructions inside the bundle unchanged, which causes inconstancy and crashes
Thumb2SizeReduction.cpp::ReduceMBB().


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199127 91177308-0d34-0410-b5e6-96231b3b80d8

Author: Weiming Zhao

lib/Target/ARM/Thumb2SizeReduction.cpp

@@ -980,6 +980,9 @@ bool Thumb2SizeReduce::ReduceMBB(MachineBasicBlock &MBB) {
       MachineOperand *MO = BundleMI->findRegisterDefOperand(ARM::CPSR);
       if (MO && !MO->isDead())
         LiveCPSR = true;
+      MO = BundleMI->findRegisterUseOperand(ARM::CPSR);
+      if (MO && !MO->isKill())
+        LiveCPSR = true;
     }
 
     bool DefCPSR = false;

test/CodeGen/Thumb2/2011-12-16-T2SizeReduceAssert.ll

@@ -1,4 +1,5 @@
 ; RUN: llc < %s -mtriple=thumbv7-apple-ios -relocation-model=pic -disable-fp-elim -mcpu=cortex-a8 
+; RUN: llc < %s -mtriple=thumbv8-none-linux-gnueabi | FileCheck %s
 
 %struct.LIST_NODE.0.16 = type { %struct.LIST_NODE.0.16*, i8* }
 
@@ -26,3 +27,24 @@ bb3:                                              ; preds = %bb2, %entry
 bb5:                                              ; preds = %bb3, %bb
   ret %struct.LIST_NODE.0.16* null
 }
+
+declare void @use(i32)
+define double @find_max_double(i32 %n, double* nocapture readonly %aa) {
+entry:
+;CHECK-LABEL: find_max_double:
+  br i1 undef, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.body, %entry
+  %0 = load double* null, align 8
+  %cmp2.6 = fcmp ogt double %0, 0.000000e+00
+  %idx.1.6 = select i1 %cmp2.6, i32 undef, i32 0
+  %idx.1.7 = select i1 undef, i32 undef, i32 %idx.1.6
+  %max.1.7 = select i1 undef, double 0.000000e+00, double undef
+  br i1 undef, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body, %entry
+  %max.0.lcssa = phi double [ undef, %entry ], [ %max.1.7, %for.body ]
+  %idx.0.lcssa = phi i32 [ 0, %entry ], [ %idx.1.7, %for.body ]
+  tail call void @use(i32 %idx.0.lcssa)
+  ret double %max.0.lcssa
+}