CodeGen: Make MachineBasicBlock::back skip to the beginning of the last bundle.

This makes front/back symmetric with begin/end, avoiding some confusion.
Added instr_front/instr_back for the old behavior, corresponding to
instr_begin/instr_end. Audited all three in-tree users of back(), all
of them look like they don't want to look inside bundles.

Fixes an assertion (PR19815) when generating debug info on mips, where a
delay slot was bundled at the end of a branch.

llvm-svn: 209580

1 files changed, 8 insertions, 9 deletions

diff --git a/llvm/lib/CodeGen/MachineVerifier.cpp b/llvm/lib/CodeGen/MachineVerifier.cpp
index 96cf719184b..66529007027 100644
--- a/llvm/lib/CodeGen/MachineVerifier.cpp
+++ b/llvm/lib/CodeGen/MachineVerifier.cpp
@@ -33,7 +33,6 @@
 #include "llvm/CodeGen/LiveVariables.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/MachineInstrBundle.h"
 #include "llvm/CodeGen/MachineMemOperand.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/IR/BasicBlock.h"
@@ -578,8 +577,8 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
         report("MBB exits via unconditional fall-through but its successor "
                "differs from its CFG successor!", MBB);
       }
-      if (!MBB->empty() && getBundleStart(&MBB->back())->isBarrier() &&
-          !TII->isPredicated(getBundleStart(&MBB->back()))) {
+      if (!MBB->empty() && (&MBB->back())->isBarrier() &&
+          !TII->isPredicated((&MBB->back()))) {
         report("MBB exits via unconditional fall-through but ends with a "
                "barrier instruction!", MBB);
       }
@@ -599,10 +598,10 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
       if (MBB->empty()) {
         report("MBB exits via unconditional branch but doesn't contain "
                "any instructions!", MBB);
-      } else if (!getBundleStart(&MBB->back())->isBarrier()) {
+      } else if (!(&MBB->back())->isBarrier()) {
         report("MBB exits via unconditional branch but doesn't end with a "
                "barrier instruction!", MBB);
-      } else if (!getBundleStart(&MBB->back())->isTerminator()) {
+      } else if (!(&MBB->back())->isTerminator()) {
         report("MBB exits via unconditional branch but the branch isn't a "
                "terminator instruction!", MBB);
       }
@@ -630,10 +629,10 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
       if (MBB->empty()) {
         report("MBB exits via conditional branch/fall-through but doesn't "
                "contain any instructions!", MBB);
-      } else if (getBundleStart(&MBB->back())->isBarrier()) {
+      } else if ((&MBB->back())->isBarrier()) {
         report("MBB exits via conditional branch/fall-through but ends with a "
                "barrier instruction!", MBB);
-      } else if (!getBundleStart(&MBB->back())->isTerminator()) {
+      } else if (!(&MBB->back())->isTerminator()) {
         report("MBB exits via conditional branch/fall-through but the branch "
                "isn't a terminator instruction!", MBB);
       }
@@ -658,10 +657,10 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
       if (MBB->empty()) {
         report("MBB exits via conditional branch/branch but doesn't "
                "contain any instructions!", MBB);
-      } else if (!getBundleStart(&MBB->back())->isBarrier()) {
+      } else if (!MBB->back().isBarrier()) {
         report("MBB exits via conditional branch/branch but doesn't end with a "
                "barrier instruction!", MBB);
-      } else if (!getBundleStart(&MBB->back())->isTerminator()) {
+      } else if (!MBB->back().isTerminator()) {
         report("MBB exits via conditional branch/branch but the branch "
                "isn't a terminator instruction!", MBB);
       }