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committedAug 11, 2016
Improve virtual register handling when computing debug information
Summary: Some backends, like WebAssembly, use virtual registers instead of physical registers. This crashes the DbgValueHistoryCalculator pass, which assumes that all registers are physical. Instead, skip virtual registers when iterating aliases, and assume that they are clobbered. Reviewers: dexonsmith, dschuff, aprantl Subscribers: yurydelendik, llvm-commits, jfb, sunfish Differential Revision: https://reviews.llvm.org/D22590 llvm-svn: 278371
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-7
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2 files changed

+85
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‎llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp

+16-7
Original file line numberDiff line numberDiff line change
@@ -31,7 +31,7 @@ static unsigned isDescribedByReg(const MachineInstr &MI) {
3131
assert(MI.isDebugValue());
3232
assert(MI.getNumOperands() == 4);
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// If location of variable is described using a register (directly or
34-
// indirecltly), this register is always a first operand.
34+
// indirectly), this register is always a first operand.
3535
return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
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}
3737

@@ -164,7 +164,9 @@ static void collectChangingRegs(const MachineFunction *MF,
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// Look for register defs and register masks. Register masks are
165165
// typically on calls and they clobber everything not in the mask.
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for (const MachineOperand &MO : MI.operands()) {
167-
if (MO.isReg() && MO.isDef() && MO.getReg()) {
167+
// Skip virtual registers since they are handled by the parent.
168+
if (MO.isReg() && MO.isDef() && MO.getReg() &&
169+
!TRI->isVirtualRegister(MO.getReg())) {
168170
for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid();
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++AI)
170172
Regs.set(*AI);
@@ -192,12 +194,18 @@ void llvm::calculateDbgValueHistory(const MachineFunction *MF,
192194
// some variables.
193195
for (const MachineOperand &MO : MI.operands()) {
194196
if (MO.isReg() && MO.isDef() && MO.getReg()) {
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// If this is a virtual register, only clobber it since it doesn't
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// have aliases.
199+
if (TRI->isVirtualRegister(MO.getReg()))
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clobberRegisterUses(RegVars, MO.getReg(), Result, MI);
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// If this is a register def operand, it may end a debug value
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// range.
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for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid();
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++AI)
199-
if (ChangingRegs.test(*AI))
200-
clobberRegisterUses(RegVars, *AI, Result, MI);
203+
else {
204+
for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid();
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++AI)
206+
if (ChangingRegs.test(*AI))
207+
clobberRegisterUses(RegVars, *AI, Result, MI);
208+
}
201209
} else if (MO.isRegMask()) {
202210
// If this is a register mask operand, clobber all debug values in
203211
// non-CSRs.
@@ -238,7 +246,8 @@ void llvm::calculateDbgValueHistory(const MachineFunction *MF,
238246
if (!MBB.empty() && &MBB != &MF->back()) {
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for (auto I = RegVars.begin(), E = RegVars.end(); I != E;) {
240248
auto CurElem = I++; // CurElem can be erased below.
241-
if (ChangingRegs.test(CurElem->first))
249+
if (TRI->isVirtualRegister(CurElem->first) ||
250+
ChangingRegs.test(CurElem->first))
242251
clobberRegisterUses(RegVars, CurElem, Result, MBB.back());
243252
}
244253
}

‎llvm/test/CodeGen/WebAssembly/dbgvalue.ll

+69
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,69 @@
1+
; RUN: llc < %s -O0 -verify-machineinstrs -mtriple=wasm32-unknown-unknown | FileCheck %s
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; CHECK: BB#0
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; CHECK: #DEBUG_VALUE: usage:self <- %vreg4
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; CHECK: BB#1
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; CHECK: DW_TAG_variable
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target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
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target triple = "wasm32-unknown-unknown"
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%0 = type opaque
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11+
@key = external local_unnamed_addr global [15 x i8], align 1
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@.str = external unnamed_addr constant [33 x i8], align 1
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; Function Attrs: nounwind
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define internal i32 @0(i8*) local_unnamed_addr !dbg !14 !type !22 {
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tail call void @llvm.dbg.value(metadata i8* %0, i64 0, metadata !21, metadata !23), !dbg !24
17+
%2 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([33 x i8], [33 x i8]* @.str, i32 0, i32 0), i8* %0), !dbg !25
18+
br i1 1, label %a, label %b
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a:
20+
%3 = add i32 %2, %2
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br label %c
22+
23+
b:
24+
%4 = sub i32 %2, %2
25+
br label %c
26+
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c:
28+
%5 = phi i32 [ %3, %a ], [ %4, %b ]
29+
%6 = add i32 ptrtoint (i32 (i8*)* @0 to i32), %5
30+
ret i32 %6, !dbg !26
31+
}
32+
33+
; Function Attrs: nounwind
34+
declare i32 @printf(i8* nocapture readonly, ...) local_unnamed_addr
35+
36+
; Function Attrs: nounwind readnone
37+
declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
38+
39+
!llvm.dbg.cu = !{!0}
40+
!llvm.module.flags = !{!11, !12}
41+
!llvm.ident = !{!13}
42+
43+
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 (trunk 273884) (llvm/trunk 273897)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3)
44+
!1 = !DIFile(filename: "crash.c", directory: "wasm/tests")
45+
!2 = !{}
46+
!3 = !{!4}
47+
!4 = distinct !DIGlobalVariable(name: "key", scope: !0, file: !1, line: 7, type: !5, isLocal: false, isDefinition: true, variable: [15 x i8]* @key)
48+
!5 = !DICompositeType(tag: DW_TAG_array_type, baseType: !6, size: 120, align: 8, elements: !9)
49+
!6 = !DIDerivedType(tag: DW_TAG_typedef, name: "uint8_t", file: !7, line: 185, baseType: !8)
50+
!7 = !DIFile(filename: "wasm/emscripten/system/include/libc/bits/alltypes.h", directory: "wasm/tests")
51+
!8 = !DIBasicType(name: "unsigned char", size: 8, align: 8, encoding: DW_ATE_unsigned_char)
52+
!9 = !{!10}
53+
!10 = !DISubrange(count: 15)
54+
!11 = !{i32 2, !"Dwarf Version", i32 4}
55+
!12 = !{i32 2, !"Debug Info Version", i32 3}
56+
!13 = !{!"clang version 3.9.0 (trunk 273884) (llvm/trunk 273897)"}
57+
!14 = distinct !DISubprogram(name: "usage", scope: !1, file: !1, line: 15, type: !15, isLocal: false, isDefinition: true, scopeLine: 15, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !20)
58+
!15 = !DISubroutineType(types: !16)
59+
!16 = !{!17, !18}
60+
!17 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
61+
!18 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !19, size: 32, align: 32)
62+
!19 = !DIBasicType(name: "char", size: 8, align: 8, encoding: DW_ATE_signed_char)
63+
!20 = !{!21}
64+
!21 = !DILocalVariable(name: "self", arg: 1, scope: !14, file: !1, line: 15, type: !18)
65+
!22 = !{i64 0, !"_ZTSFiPcE"}
66+
!23 = !DIExpression()
67+
!24 = !DILocation(line: 15, column: 17, scope: !14)
68+
!25 = !DILocation(line: 16, column: 3, scope: !14)
69+
!26 = !DILocation(line: 17, column: 3, scope: !14)

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