[llvm] r223401 - Debug info: If the RegisterCoalescer::reMaterializeTrivialDef() is
David Blaikie
dblaikie at gmail.com
Thu Dec 4 15:17:24 PST 2014
On Thu, Dec 4, 2014 at 3:08 PM, Adrian Prantl <aprantl at apple.com> wrote:
>
> > On Dec 4, 2014, at 3:01 PM, David Blaikie <dblaikie at gmail.com> wrote:
> >
> >
> >
> > On Thu, Dec 4, 2014 at 2:59 PM, Adrian Prantl <aprantl at apple.com> wrote:
> >
> > > On Dec 4, 2014, at 2:35 PM, David Blaikie <dblaikie at gmail.com> wrote:
> > >
> > >
> > >
> > > On Thu, Dec 4, 2014 at 2:29 PM, Adrian Prantl <aprantl at apple.com>
> wrote:
> > > Author: adrian
> > > Date: Thu Dec 4 16:29:04 2014
> > > New Revision: 223401
> > >
> > > URL: http://llvm.org/viewvc/llvm-project?rev=223401&view=rev
> > > Log:
> > > Debug info: If the RegisterCoalescer::reMaterializeTrivialDef() is
> > > eliminating all uses of a vreg, update any DBG_VALUE describing that
> vreg
> > > to point to the rematerialized register instead.
> > >
> > > Added:
> > > llvm/trunk/test/DebugInfo/AArch64/coalescing.ll
> > > Modified:
> > > llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp
> > >
> > > Modified: llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp
> > > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp?rev=223401&r1=223400&r2=223401&view=diff
> > >
> ==============================================================================
> > > --- llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp (original)
> > > +++ llvm/trunk/lib/CodeGen/RegisterCoalescer.cpp Thu Dec 4 16:29:04
> 2014
> > > @@ -898,8 +898,20 @@ bool RegisterCoalescer::reMaterializeTri
> > >
> > > // The source interval can become smaller because we removed a use.
> > > LIS->shrinkToUses(&SrcInt, &DeadDefs);
> > > - if (!DeadDefs.empty())
> > > + if (!DeadDefs.empty()) {
> > > + // If the virtual SrcReg is completely eliminated, update all
> DBG_VALUEs
> > > + // to describe DstReg instead.
> > > + for (MachineRegisterInfo::use_iterator UI =
> MRI->use_begin(SrcReg),
> > > + UE = MRI->use_end(); UI != UE; ++UI) {
> > >
> > > range-for with use_operands?
> >
> > Updated in r223405. Looks much nicer, thanks!
> >
> > >
> > > + MachineOperand &UseMO = *UI;
> > > + MachineInstr *UseMI = UseMO.getParent();
> > > + if (UseMI->isDebugValue()) {
> > > + UseMO.setReg(DstReg);
> > > + DEBUG({dbgs() << "\t\tupdated: " << *UseMI;});
> > > + }
> > > + }
> > > eliminateDeadDefs();
> > > + }
> > >
> > > return true;
> > > }
> > >
> > > Added: llvm/trunk/test/DebugInfo/AArch64/coalescing.ll
> > > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/AArch64/coalescing.ll?rev=223401&view=auto
> > >
> ==============================================================================
> > > --- llvm/trunk/test/DebugInfo/AArch64/coalescing.ll (added)
> > > +++ llvm/trunk/test/DebugInfo/AArch64/coalescing.ll Thu Dec 4
> 16:29:04 2014
> > > @@ -0,0 +1,70 @@
> > > +; RUN: llc -filetype=obj %s -o - | llvm-dwarfdump - | FileCheck %s
> > > +;
> > > +; Generated at -Os from:
> > > +; void *my_memcpy(void *dst, const void * src, long n);
> > > +; void* getBytesNoCopy();
> > > +; void start() {
> > > +; unsigned size;
> > > +; my_memcpy(&size, getBytesNoCopy(), sizeof(size));
> > >
> > > are all of these parameters needed? Any idea what the interactions are?
> > We can safely omit the last two arguments.
> >
> > Could you remove them & anything else that's not needed to reproduce
> this issue? (optionally, in addition, I usually find it a bit easier to
> remove the original source identifiers and just use foo/bar/baz/etc - so
> that there's no confusion about existing/previous semantics of the
> functions that aren't relevant to the test)
>
> Sorry, I forgot to mention, I did remove them in r223405, too :-)
> >
> > >
> > > +; if (size != 0) { }
> > >
> > > Sort of surprised this code isn't DCE'd by -Os?
> >
> > This is an unrelated, but still interesting bug. If the value isn’t used
> after the call, we’re dropping the dbg.value entirely. Nevermind that the
> actual used is still being optimized away.
> >
> > It'd be nice to leave it out of an unrelated test, so that it's easier
> to tell what this test is meant to test when code changes affect its
> results, etc.
>
> Well, I like to put the source code that a testcase was derived from in
> the comment, and that line *is* necessary to get to the IR in the testcase.
Right, sorry, perhaps I was unclear earlier: Is that line necessary to
reproduce the bug/fix you committed? If so, yeah, keep it there (if not,
remove it from the source comment and the IR) - I'm still surprised it's
necessary to reproduce the bug, I would've expected it to be DCE'd long
before it made a difference to register coalescing.
- David
> I’d rather add a comment than remove the line.
>
> -- adrian
>
> >
> >
> > >
> > > +; }
> > > +
> > > +; ModuleID = 'test1.cpp'
> > > +target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
> > > +target triple = "arm64-apple-ios"
> > > +
> > > +; Function Attrs: nounwind optsize
> > > +define void @_Z5startv() #0 {
> > > +entry:
> > > + %size = alloca i32, align 4
> > > + %0 = bitcast i32* %size to i8*, !dbg !15
> > > + %call = tail call i8* @_Z14getBytesNoCopyv() #3, !dbg !16
> > > + %call1 = call i8* @_Z9my_memcpyPvPKvl(i8* %0, i8* %call, i64 4) #3,
> !dbg !15
> > > + call void @llvm.dbg.value(metadata !{i32* %size}, i64 0, metadata
> !10, metadata !17), !dbg !18
> > > + ; CHECK: .debug_info contents:
> > > + ; CHECK: DW_TAG_variable
> > > + ; CHECK-NEXT: DW_AT_location
> > > + ; CHECK-NEXT: DW_AT_name {{.*}}"size"
> > > + ; CHECK: .debug_loc contents:
> > > + ; CHECK: Location description: 70 00
> > > + ret void, !dbg !19
> > > +}
> > > +
> > > +; Function Attrs: optsize
> > > +declare i8* @_Z9my_memcpyPvPKvl(i8*, i8*, i64) #1
> > > +
> > > +; Function Attrs: optsize
> > > +declare i8* @_Z14getBytesNoCopyv() #1
> > > +
> > > +; Function Attrs: nounwind readnone
> > > +declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #2
> > > +
> > > +attributes #0 = { nounwind optsize }
> > > +attributes #1 = { optsize }
> > > +attributes #2 = { nounwind readnone }
> > > +attributes #3 = { nounwind optsize }
> > > +
> > > +!llvm.dbg.cu = !{!0}
> > > +!llvm.module.flags = !{!12, !13}
> > > +!llvm.ident = !{!14}
> > > +
> > > +!0 = metadata !{metadata !"0x11\004\00clang version 3.6.0 (trunk
> 223149) (llvm/trunk 223153)\001\00\000\00\001", metadata !1, metadata !2,
> metadata !2, metadata !3, metadata !2, metadata !2} ; [ DW_TAG_compile_unit
> ] [/<stdin>] [DW_LANG_C_plus_plus]
> > > +!1 = metadata !{metadata !"<stdin>", metadata !""}
> > > +!2 = metadata !{}
> > > +!3 = metadata !{metadata !4}
> > > +!4 = metadata !{metadata
> !"0x2e\00start\00start\00_Z5startv\003\000\001\000\000\00256\001\004",
> metadata !5, metadata !6, metadata !7, null, void ()* @_Z5startv, null,
> null, metadata !9} ; [ DW_TAG_subprogram ] [line 3] [def] [scope 4] [start]
> > > +!5 = metadata !{metadata !"test1.cpp", metadata !""}
> > > +!6 = metadata !{metadata !"0x29", metadata !5} ; [
> DW_TAG_file_type ] [/test1.cpp]
> > > +!7 = metadata !{metadata !"0x15\00\000\000\000\000\000\000", null,
> null, null, metadata !8, null, null, null} ; [ DW_TAG_subroutine_type ]
> [line 0, size 0, align 0, offset 0] [from ]
> > > +!8 = metadata !{null}
> > > +!9 = metadata !{metadata !10}
> > > +!10 = metadata !{metadata !"0x100\00size\005\000", metadata !4,
> metadata !6, metadata !11} ; [ DW_TAG_auto_variable ] [size] [line 5]
> > > +!11 = metadata !{metadata !"0x24\00unsigned
> int\000\0032\0032\000\000\007", null, null} ; [ DW_TAG_base_type ]
> [unsigned int] [line 0, size 32, align 32, offset 0, enc DW_ATE_unsigned]
> > > +!12 = metadata !{i32 2, metadata !"Dwarf Version", i32 2}
> > > +!13 = metadata !{i32 2, metadata !"Debug Info Version", i32 2}
> > > +!14 = metadata !{metadata !"clang version 3.6.0 (trunk 223149)
> (llvm/trunk 223153)"}
> > > +!15 = metadata !{i32 6, i32 3, metadata !4, null}
> > > +!16 = metadata !{i32 6, i32 25, metadata !4, null}
> > > +!17 = metadata !{metadata !"0x102"} ; [
> DW_TAG_expression ]
> > > +!18 = metadata !{i32 5, i32 12, metadata !4, null}
> > > +!19 = metadata !{i32 9, i32 1, metadata !4, null}
> > >
> > >
> > > _______________________________________________
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> > > llvm-commits at cs.uiuc.edu
> > > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> > >
> >
> >
>
>
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