[llvm] r351719 - Revert "[AVR] Insert unconditional branch when inserting MBBs between blocks with fallthrough"

[Dylan McKay via llvm-commits]

Author: dylanmckay
Date: Sun Jan 20 18:46:13 2019
New Revision: 351719

URL: http://llvm.org/viewvc/llvm-project?rev=351719&view=rev
Log:
Revert "[AVR] Insert unconditional branch when inserting MBBs between blocks with fallthrough"

This reverts commit r351718.

Carl pointed out that the unit test could be improved.

This patch will be recommitted once the test is made more resilient.

Removed:
    llvm/trunk/test/CodeGen/AVR/avr-rust-issue-123.ll
Modified:
    llvm/trunk/lib/Target/AVR/AVRISelLowering.cpp

Modified: llvm/trunk/lib/Target/AVR/AVRISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AVR/AVRISelLowering.cpp?rev=351719&r1=351718&r2=351719&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AVR/AVRISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/AVR/AVRISelLowering.cpp Sun Jan 20 18:46:13 2019
@@ -1634,15 +1634,6 @@ AVRTargetLowering::EmitInstrWithCustomIn
 
   MachineFunction *MF = MBB->getParent();
   const BasicBlock *LLVM_BB = MBB->getBasicBlock();
-  MachineBasicBlock *FallThrough = MBB->getFallThrough();
-
-  // If the current basic block falls through to another basic block,
-  // we must insert an unconditional branch to the fallthrough destination
-  // if we are to insert basic blocks at the prior fallthrough point.
-  if (FallThrough != nullptr) {
-    BuildMI(MBB, dl, TII.get(AVR::RJMPk)).addMBB(FallThrough);
-  }
-
   MachineBasicBlock *trueMBB = MF->CreateMachineBasicBlock(LLVM_BB);
   MachineBasicBlock *falseMBB = MF->CreateMachineBasicBlock(LLVM_BB);
 

Removed: llvm/trunk/test/CodeGen/AVR/avr-rust-issue-123.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AVR/avr-rust-issue-123.ll?rev=351718&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AVR/avr-rust-issue-123.ll (original)
+++ llvm/trunk/test/CodeGen/AVR/avr-rust-issue-123.ll (removed)
@@ -1,65 +0,0 @@
-; RUN: llc -O1 < %s -march=avr | FileCheck %s
-
-; This test ensures that the Select8/Select16 expansion
-; pass inserts an unconditional branch to the previous adjacent
-; basic block when inserting new basic blocks when the
-; prior block has a fallthrough.
-;
-; Before this bug was fixed, Select8/Select16 expansion
-; would leave a dangling fallthrough to an undefined block.
-;
-; The BranchFolding pass would later rearrange the basic
-; blocks based on predecessor/successor list assumptions
-; which were made incorrect due to the invalid Select
-; expansion.
-
-; More information in
-; https://github.com/avr-rust/rust/issues/123.
-
-%UInt8 = type <{ i8 }>
-%UInt32 = type <{ i32 }>
-%Sb = type <{ i1 }>
-
- at delayFactor = hidden global %UInt8 zeroinitializer, align 1
- at delay = hidden global %UInt32 zeroinitializer, align 4
- at flag = hidden global %Sb zeroinitializer, align 1
-
-declare void @eeprom_write(i16, i8)
-
-define hidden void @update_register(i8 %arg, i8 %arg1) {
-entry:
-  switch i8 %arg, label %bb7 [
-    i8 6, label %bb
-    i8 7, label %bb6
-  ]
-
-bb:                                               ; preds = %entry
-  %tmp = icmp ugt i8 %arg1, 90
-  %tmp2 = icmp ult i8 %arg1, 5
-  %. = select i1 %tmp2, i8 5, i8 %arg1
-  %tmp3 = select i1 %tmp, i8 90, i8 %.
-  store i8 %tmp3, i8* getelementptr inbounds (%UInt8, %UInt8* @delayFactor, i64 0, i32 0), align 1
-  %tmp4 = zext i8 %tmp3 to i32
-  %tmp5 = mul nuw nsw i32 %tmp4, 100
-  store i32 %tmp5, i32* getelementptr inbounds (%UInt32, %UInt32* @delay, i64 0, i32 0), align 4
-  tail call void @eeprom_write(i16 34, i8 %tmp3)
-  br label %bb7
-
-bb6:                                              ; preds = %entry
-  %not. = icmp ne i8 %arg1, 0
-  %.2 = zext i1 %not. to i8
-  store i1 %not., i1* getelementptr inbounds (%Sb, %Sb* @flag, i64 0, i32 0), align 1
-
-  ; CHECK: LBB0_{{[0-9]+}}:
-  ; CHECK: call eeprom_write
-  ; CHECK-NEXT: LBB0_{{[0-9]+}}
-  ; CHECK-NEXT: pop r{{[0-9]+}}
-  ; CHECK-NEXT: ret
-
-  tail call void @eeprom_write(i16 35, i8 %.2)
-  br label %bb7
-
-bb7:                                              ; preds = %bb6, %bb, %entry
-  ret void
-}
-