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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209580 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/MachineBasicBlock.h b/include/llvm/CodeGen/MachineBasicBlock.h
index 8709d86fe4435d5d4d37706359e167e2ff060a87..90bdeee46d267978a4f009406be78f9b39ab93b3 100644 (file)
--- a/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/include/llvm/CodeGen/MachineBasicBlock.h
@@ -219,10 +219,15 @@ public:
   unsigned size() const { return (unsigned)Insts.size(); }
   bool empty() const { return Insts.empty(); }
 
-  MachineInstr& front() { return Insts.front(); }
-  MachineInstr& back()  { return Insts.back(); }
-  const MachineInstr& front() const { return Insts.front(); }
-  const MachineInstr& back()  const { return Insts.back(); }
+  MachineInstr       &instr_front()       { return Insts.front(); }
+  MachineInstr       &instr_back()        { return Insts.back();  }
+  const MachineInstr &instr_front() const { return Insts.front(); }
+  const MachineInstr &instr_back()  const { return Insts.back();  }
+
+  MachineInstr       &front()             { return Insts.front(); }
+  MachineInstr       &back()              { return *--end();      }
+  const MachineInstr &front()       const { return Insts.front(); }
+  const MachineInstr &back()        const { return *--end();      }
 
   instr_iterator                instr_begin()       { return Insts.begin();  }
   const_instr_iterator          instr_begin() const { return Insts.begin();  }

diff --git a/lib/CodeGen/MachineVerifier.cpp b/lib/CodeGen/MachineVerifier.cpp
index 96cf719184be49530954c49ef350661f96624a72..665290070273b21c82b9f5e0d715498e607bf347 100644 (file)
--- a/lib/CodeGen/MachineVerifier.cpp
+++ b/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);
       }

diff --git a/test/DebugInfo/Mips/delay-slot.ll b/test/DebugInfo/Mips/delay-slot.ll
new file mode 100644 (file)
index 0000000..9bce4ba
--- /dev/null
+++ b/test/DebugInfo/Mips/delay-slot.ll
@@ -0,0 +1,75 @@
+; RUN: llc -filetype=obj -O0 < %s -mtriple mips-unknown-linux-gnu | llvm-dwarfdump - | FileCheck %s
+; PR19815
+
+; Generated using clang -target mips-linux-gnu -g test.c -S -o - -flto|opt -sroa -S
+; test.c:
+;
+; int foo(int x) {
+;  if (x)
+;    return 0;
+;  return 1;
+; }
+
+; CHECK: Address            Line   Column File   ISA Discriminator Flags
+; CHECK: ------------------ ------ ------ ------ --- ------------- -------------
+; CHECK: 0x0000000000000000      1      0      1   0             0  is_stmt
+; CHECK: 0x0000000000000000      1      0      1   0             0  is_stmt prologue_end
+; CHECK: 0x0000000000000008      2      0      1   0             0  is_stmt
+; CHECK: 0x0000000000000020      3      0      1   0             0  is_stmt
+; CHECK: 0x0000000000000030      4      0      1   0             0  is_stmt
+; CHECK: 0x0000000000000040      5      0      1   0             0  is_stmt
+; CHECK: 0x0000000000000050      5      0      1   0             0  is_stmt end_sequence
+
+target datalayout = "E-m:m-p:32:32-i8:8:32-i16:16:32-i64:64-n32-S64"
+target triple = "mips--linux-gnu"
+
+; Function Attrs: nounwind
+define i32 @foo(i32 %x) #0 {
+entry:
+  call void @llvm.dbg.value(metadata !{i32 %x}, i64 0, metadata !12), !dbg !13
+  %tobool = icmp ne i32 %x, 0, !dbg !14
+  br i1 %tobool, label %if.then, label %if.end, !dbg !14
+
+if.then:                                          ; preds = %entry
+  br label %return, !dbg !16
+
+if.end:                                           ; preds = %entry
+  br label %return, !dbg !17
+
+return:                                           ; preds = %if.end, %if.then
+  %retval.0 = phi i32 [ 0, %if.then ], [ 1, %if.end ]
+  ret i32 %retval.0, !dbg !18
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata) #1
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata) #1
+
+attributes #0 = { nounwind }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9, !10}
+!llvm.ident = !{!11}
+
+!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.5.0 ", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !"", i32 1} ; [ DW_TAG_compile_unit ] [/tmp/test.c] [DW_LANG_C99]
+!1 = metadata !{metadata !"test.c", metadata !"/tmp"}
+!2 = metadata !{}
+!3 = metadata !{metadata !4}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"foo", metadata !"foo", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, i32 (i32)* @foo, null, null, metadata !2, i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [foo]
+!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [/tmp/test.c]
+!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{metadata !8, metadata !8}
+!8 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!9 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
+!10 = metadata !{i32 2, metadata !"Debug Info Version", i32 1}
+!11 = metadata !{metadata !"clang version 3.5.0"}
+!12 = metadata !{i32 786689, metadata !4, metadata !"x", metadata !5, i32 16777217, metadata !8, i32 0, i32 0} ; [ DW_TAG_arg_variable ] [x] [line 1]
+!13 = metadata !{i32 1, i32 0, metadata !4, null}
+!14 = metadata !{i32 2, i32 0, metadata !15, null}
+!15 = metadata !{i32 786443, metadata !1, metadata !4, i32 2, i32 0, i32 0, i32 0} ; [ DW_TAG_lexical_block ] [/tmp/test.c]
+!16 = metadata !{i32 3, i32 0, metadata !15, null}
+!17 = metadata !{i32 4, i32 0, metadata !4, null}
+!18 = metadata !{i32 5, i32 0, metadata !4, null}

diff --git a/test/DebugInfo/Mips/lit.local.cfg b/test/DebugInfo/Mips/lit.local.cfg
new file mode 100644 (file)
index 0000000..88262fb
--- /dev/null
+++ b/test/DebugInfo/Mips/lit.local.cfg
@@ -0,0 +1,3 @@
+targets = set(config.root.targets_to_build.split())
+if not 'Mips' in targets:
+    config.unsupported = True