[ARM] Remove a dead ADD during the creation of TBBs

During the optimisation of jump tables in the constant island pass,
an extra ADD could be left over, now dead but not removed.

Differential Revision: https://reviews.llvm.org/D31389

llvm-svn: 299634

1 files changed, 124 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/Thumb2/tbb-removeadd.mir b/llvm/test/CodeGen/Thumb2/tbb-removeadd.mir
new file mode 100644
index 00000000000..89ed9872053
--- /dev/null
+++ b/llvm/test/CodeGen/Thumb2/tbb-removeadd.mir
@@ -0,0 +1,124 @@
+#RUN: llc -run-pass arm-cp-islands %s -o - | FileCheck %s
+
+--- |
+  ; ModuleID = 'test.ll'
+  source_filename = "test.c"
+  target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+  target triple = "thumbv8r-arm-none-eabi"
+  
+  define void @Func(i32 %i, i32* nocapture %p) local_unnamed_addr {
+  entry:
+    switch i32 %i, label %sw.epilog [
+      i32 0, label %sw.bb
+      i32 1, label %sw.bb1
+      i32 2, label %sw.epilog.sink.split
+      i32 4, label %sw.bb3
+    ]
+  
+  sw.bb:                                            ; preds = %entry
+    br label %sw.epilog.sink.split
+  
+  sw.bb1:                                           ; preds = %entry
+    store i32 0, i32* %p, align 4
+    br label %sw.epilog.sink.split
+  
+  sw.bb3:                                           ; preds = %entry
+    br label %sw.epilog.sink.split
+  
+  sw.epilog.sink.split:                             ; preds = %sw.bb3, %sw.bb1, %sw.bb, %entry
+    %.sink = phi i32 [ 2, %sw.bb3 ], [ 0, %sw.bb ], [ 1, %entry ], [ 1, %sw.bb1 ]
+    store i32 %.sink, i32* %p, align 4
+    br label %sw.epilog
+  
+  sw.epilog:                                        ; preds = %sw.epilog.sink.split, %entry
+    ret void
+  }
+
+...
+---
+name:            Func
+alignment:       1
+exposesReturnsTwice: false
+noVRegs:         true
+legalized:       false
+regBankSelected: false
+selected:        false
+tracksRegLiveness: true
+liveins:         
+  - { reg: '%r0' }
+  - { reg: '%r1' }
+frameInfo:       
+  isFrameAddressTaken: false
+  isReturnAddressTaken: false
+  hasStackMap:     false
+  hasPatchPoint:   false
+  stackSize:       0
+  offsetAdjustment: 0
+  maxAlignment:    0
+  adjustsStack:    false
+  hasCalls:        false
+  maxCallFrameSize: 0
+  hasOpaqueSPAdjustment: false
+  hasVAStart:      false
+  hasMustTailInVarArgFunc: false
+jumpTable:       
+  kind:            inline
+  entries:         
+    - id:              0
+      blocks:          [ '%bb.2.sw.bb', '%bb.3.sw.bb1', '%bb.5.sw.epilog.sink.split', 
+                         '%bb.6.sw.epilog', '%bb.4.sw.bb3' ]
+# The ADD should be deleted along with the LEA
+# CHECK-NOT: t2LEApcrelJT
+# CHECK-NOT: t2ADDrs
+# CHECK: tMOVi8
+# CHECK: t2TBB_JT
+
+body:             |
+  bb.0.entry:
+    successors: %bb.6.sw.epilog(0x0ccccccb), %bb.1.entry(0x73333335)
+    liveins: %r0, %r1
+  
+    tCMPi8 %r0, 4, 14, _, implicit-def %cpsr
+    t2Bcc %bb.6.sw.epilog, 8, killed %cpsr
+  
+  bb.1.entry:
+    successors: %bb.2.sw.bb(0x1c71c71c), %bb.3.sw.bb1(0x1c71c71c), %bb.5.sw.epilog.sink.split(0x1c71c71c), %bb.6.sw.epilog(0x0e38e38e), %bb.4.sw.bb3(0x1c71c71c)
+    liveins: %r0, %r1
+  
+    %r2 = t2LEApcrelJT %jump-table.0, 14, _
+    %r3 = t2ADDrs killed %r2, %r0, 18, 14, _, _
+    %r2, dead %cpsr = tMOVi8 1, 14, _
+    t2BR_JT killed %r3, killed %r0, %jump-table.0
+  
+  bb.2.sw.bb:
+    successors: %bb.5.sw.epilog.sink.split(0x80000000)
+    liveins: %r1
+  
+    %r2, dead %cpsr = tMOVi8 0, 14, _
+    t2B %bb.5.sw.epilog.sink.split, 14, _
+  
+  bb.3.sw.bb1:
+    successors: %bb.5.sw.epilog.sink.split(0x80000000)
+    liveins: %r1
+  
+    %r0, dead %cpsr = tMOVi8 0, 14, _
+    %r2, dead %cpsr = tMOVi8 1, 14, _
+    tSTRi killed %r0, %r1, 0, 14, _ :: (store 4 into %ir.p)
+    t2B %bb.5.sw.epilog.sink.split, 14, _
+  
+  bb.4.sw.bb3:
+    successors: %bb.5.sw.epilog.sink.split(0x80000000)
+    liveins: %r1
+  
+    %r2, dead %cpsr = tMOVi8 2, 14, _
+  
+  bb.5.sw.epilog.sink.split:
+    successors: %bb.6.sw.epilog(0x80000000)
+    liveins: %r1, %r2
+  
+    tSTRi killed %r2, killed %r1, 0, 14, _ :: (store 4 into %ir.p)
+  
+  bb.6.sw.epilog:
+    tBX_RET 14, _
+
+...