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CodeGen: Make MachineBasicBlock::back skip to the beginning of the la…
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…st 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
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@d0k
d0k committed May 24, 2014
1 parent 29f94c7 commit 9d934ac
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Showing 4 changed files with 95 additions and 13 deletions.
13 changes: 9 additions & 4 deletions include/llvm/CodeGen/MachineBasicBlock.h
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Original file line number Diff line number Diff line change
Expand Up @@ -219,10 +219,15 @@ class MachineBasicBlock : public ilist_node<MachineBasicBlock> {
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(); }
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17 changes: 8 additions & 9 deletions lib/CodeGen/MachineVerifier.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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"
Expand Down Expand Up @@ -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);
}
Expand All @@ -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);
}
Expand Down Expand Up @@ -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);
}
Expand All @@ -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);
}
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75 changes: 75 additions & 0 deletions test/DebugInfo/Mips/delay-slot.ll
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Original file line number Diff line number Diff line change
@@ -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}
3 changes: 3 additions & 0 deletions test/DebugInfo/Mips/lit.local.cfg
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
targets = set(config.root.targets_to_build.split())
if not 'Mips' in targets:
config.unsupported = True

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