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[PatchableFunction] Use an empty DebugLoc

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The current FirstMI.getDebugLoc() is actually null in almost all cases.
If it isn't, the generated .loc will be considered initial. The .loc
will have the prologue_end flag and terminate the prologue prematurely.

Also use an overload of BuildMI that will not prepend
PATCHABLE_FUNCTION_ENTRY to a MachineInstr bundle.
This commit is contained in:
Fangrui Song 2020-02-01 13:28:19 -08:00
parent 7fa671ec47
commit f822a05a88
2 changed files with 6 additions and 36 deletions
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11
lib/CodeGen/PatchableFunction.cpp
View File

@ -58,14 +58,9 @@ bool PatchableFunction::runOnMachineFunction(MachineFunction &MF) {
if (MF.getFunction().hasFnAttribute("patchable-function-entry")) { if (MF.getFunction().hasFnAttribute("patchable-function-entry")) {
MachineBasicBlock &FirstMBB = *MF.begin(); MachineBasicBlock &FirstMBB = *MF.begin();
const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo(); const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
if (FirstMBB.empty()) { // The initial .loc covers PATCHABLE_FUNCTION_ENTER.
BuildMI(&FirstMBB, DebugLoc(), BuildMI(FirstMBB, FirstMBB.begin(), DebugLoc(),
TII->get(TargetOpcode::PATCHABLE_FUNCTION_ENTER)); TII->get(TargetOpcode::PATCHABLE_FUNCTION_ENTER));
} else {
MachineInstr &FirstMI = *FirstMBB.begin();
BuildMI(FirstMBB, FirstMI, FirstMI.getDebugLoc(),
TII->get(TargetOpcode::PATCHABLE_FUNCTION_ENTER));
}
return true; return true;
} }

31
test/CodeGen/AArch64/patchable-function-entry-empty.mir
View File

@ -1,15 +1,11 @@
# RUN: llc -mtriple=aarch64 -run-pass=patchable-function %s -o - | FileCheck %s # RUN: llc -mtriple=aarch64 -run-pass=patchable-function %s -o - | FileCheck %s
## The initial .loc covers PATCHABLE_FUNCTION_ENTER.
## Emitting a new .loc may create a prologue_end prematurely.
# CHECK: name: empty # CHECK: name: empty
# CHECK: bb.0.entry # CHECK: bb.0.entry
# CHECK: PATCHABLE_FUNCTION_ENTER debug-location !DILocation(line: 1,
# CHECK-NEXT: RET undef $lr, debug-location !DILocation(line: 1,
## Empty entry MBB, no debug location.
# CHECK: name: empty_entry
# CHECK: bb.0.entry
# CHECK: PATCHABLE_FUNCTION_ENTER{{$}} # CHECK: PATCHABLE_FUNCTION_ENTER{{$}}
# CHECK: bb.1.here # CHECK-NEXT: RET undef $lr, debug-location !DILocation(line: 1,
--- | --- |
define void @empty() #0 !dbg !7 { define void @empty() #0 !dbg !7 {
@ -17,13 +13,6 @@
ret void, !dbg !10 ret void, !dbg !10
} }
define void @empty_entry() #0 !dbg !11 {
entry:
br label %here
here:
ret void, !dbg !12
}
attributes #0 = { "patchable-function-entry"="1" } attributes #0 = { "patchable-function-entry"="1" }
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 11.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None) !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 11.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "a.c", directory: "/tmp") !1 = !DIFile(filename: "a.c", directory: "/tmp")
@ -36,8 +25,6 @@
!8 = !DISubroutineType(types: !9) !8 = !DISubroutineType(types: !9)
!9 = !{null} !9 = !{null}
!10 = !DILocation(line: 1, column: 61, scope: !7) !10 = !DILocation(line: 1, column: 61, scope: !7)
!11 = distinct !DISubprogram(name: "empty_entry", scope: !1, file: !1, line: 2, type: !8, scopeLine: 2, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
!12 = !DILocation(line: 2, column: 61, scope: !11)
... ...
--- ---
@ -50,15 +37,3 @@ body: |
RET undef $lr, debug-location !10 RET undef $lr, debug-location !10
... ...
---
name: empty_entry
alignment: 4
tracksRegLiveness: true
body: |
bb.0.entry:
liveins: $lr
bb.1.here:
liveins: $lr
RET undef $lr, debug-location !12
...