[llvm-bugs] [Bug 38899] New: [DebugInfo] DBG_VALUE for spill is emitted before the spill is performed
via llvm-bugs
llvm-bugs at lists.llvm.org
Mon Sep 10 23:25:19 PDT 2018
https://bugs.llvm.org/show_bug.cgi?id=38899
Bug ID: 38899
Summary: [DebugInfo] DBG_VALUE for spill is emitted before the
spill is performed
Product: new-bugs
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: new bugs
Assignee: unassignedbugs at nondot.org
Reporter: david.stenberg at ericsson.com
CC: llvm-bugs at lists.llvm.org
Created attachment 20865
--> https://bugs.llvm.org/attachment.cgi?id=20865&action=edit
C reproducer.
Reproduced on trunk (r341822).
When compiling the attached C file using:
clang -O3 -g foo.c -S --target=ppc64 -S -emit-llvm -o foo.ll
llc -O3 foo.ll -o foo.mir -print-before-all -print-after-all -debug
-stop-after=virtregrewriter &> foo.log
we get a spurious DBG_VALUE emitted for the variable c after register
allocation.
Before Debug Variable Analysis:
# *** IR Dump Before Debug Variable Analysis ***:
# Machine code for function test: NoPHIs, TracksLiveness
Function Live Ins: $x3 in %0, $x4 in %1
0B bb.0.entry:
liveins: $x3, $x4
DBG_VALUE debug-use $x3, debug-use $noreg, !"a",
!DIExpression(), debug-location !16; foo.c:8:14 line no:8
DBG_VALUE debug-use $x4, debug-use $noreg, !"b",
!DIExpression(), debug-location !17; foo.c:8:21 line no:8
16B %1:g8rc = COPY $x4
DBG_VALUE debug-use %1:g8rc, debug-use $noreg, !"b",
!DIExpression(), debug-location !17; foo.c:8:21 line no:8
32B %0:g8rc = COPY $x3
DBG_VALUE debug-use %0:g8rc, debug-use $noreg, !"a",
!DIExpression(), debug-location !16; foo.c:8:14 line no:8
DBG_VALUE debug-use %0.sub_32:g8rc, debug-use $noreg, !"a",
!DIExpression(), debug-location !16; foo.c:8:14 line no:8
DBG_VALUE debug-use %1.sub_32:g8rc, debug-use $noreg, !"b",
!DIExpression(), debug-location !17; foo.c:8:21 line no:8
80B %4:gprc = MULLW %1.sub_32:g8rc, %0.sub_32:g8rc,
debug-location !18; foo.c:9:13
DBG_VALUE debug-use %4:gprc, debug-use $noreg, !"c",
!DIExpression(), debug-location !19; foo.c:9:7 line no:9
96B INLINEASM &"" [sideeffect] [attdialect], $0:[clobber], {{{
implicit-def early-clobber of $r0-$r1 omitted }}}, !25, debug-location !20;
foo.c:2:3 @[ foo.c:10:3 ]
112B %5:g8rc = EXTSW_32_64 %4:gprc, debug-location !26; foo.c:11:3
128B $x3 = COPY %5:g8rc, debug-location !26; foo.c:11:3
144B BLR8 implicit $lr8, implicit $rm, implicit $x3,
debug-location !26; foo.c:11:3
# End machine code for function test.
********** COMPUTING LIVE DEBUG VARIABLES: test **********
********** DEBUG VARIABLES **********
!"a,8" [0B;0e):0 [80B;80r):2 Loc0=debug-use $x3 Loc1=debug-use %0
Loc2=debug-use %0.sub_32
!"b,8" [0B;0e):0 [16r;32r):1 [80B;80r):2 Loc0=debug-use $x4
Loc1=debug-use %1 Loc2=debug-use %1.sub_32
!"c,9" [80r;112r):0 Loc0=debug-use %4
and after Virtual Register Rewriter:
********** EMITTING LIVE DEBUG VARIABLES **********
!"a,8" [0B;0e):0 [80B;80r):2 Loc0=debug-use $x3 Loc1=debug-use %0
Loc2=debug-use %0.sub_32
[0B;0e):0 %bb.0-160B
[64B;80r):1 %bb.0-160B
!"b,8" [0B;0e):0 [16r;32r):1 [80B;80r):2 Loc0=debug-use $x4
Loc1=debug-use %1 Loc2=debug-use %1.sub_32
[0B;0e):0 %bb.0-160B
[16r;32r):0 %bb.0-160B
[64B;80r):1 %bb.0-160B
!"c,9" [80r;112r):0 Loc0=debug-use %4
[80r;112r):0 %bb.0-160B
# *** IR Dump After Virtual Register Rewriter ***:
# Machine code for function test: NoPHIs, TracksLiveness, NoVRegs
Frame Objects:
fi#0: size=4, align=4, at location [SP]
Function Live Ins: $x3, $x4
bb.0.entry:
liveins: $x3, $x4
DBG_VALUE debug-use $x3, debug-use $noreg, !"a", !DIExpression(),
debug-location !16; foo.c:8:14 line no:8
DBG_VALUE debug-use $r3, debug-use $noreg, !"a", !DIExpression(),
debug-location !16; foo.c:8:14 line no:8
DBG_VALUE debug-use $x4, debug-use $noreg, !"b", !DIExpression(),
debug-location !17; foo.c:8:21 line no:8
DBG_VALUE debug-use $x4, debug-use $noreg, !"b", !DIExpression(),
debug-location !17; foo.c:8:21 line no:8
DBG_VALUE debug-use $r4, debug-use $noreg, !"b", !DIExpression(),
debug-location !17; foo.c:8:21 line no:8
renamable $r3 = MULLW renamable $r4, renamable $r3, implicit killed
$x3, implicit killed $x4, debug-location !18; foo.c:9:13
DBG_VALUE %stack.0, 0, !"c", !DIExpression(), debug-location !19;
foo.c:9:7 line no:9
STW killed renamable $r3, 0, %stack.0 :: (store 4 into %stack.0)
INLINEASM &"" [sideeffect] [attdialect], $0:[clobber], {{{
implicit-def early-clobber of $r0-$r1 omitted }}}, !25, debug-location !20;
foo.c:2:3 @[ foo.c:10:3 ]
renamable $r3 = LWZ 0, %stack.0, debug-location !26 :: (load 4 from
%stack.0); foo.c:11:3
renamable $x3 = EXTSW_32_64 killed renamable $r3, debug-location !26;
foo.c:11:3
BLR8 implicit $lr8, implicit $rm, implicit $x3, debug-location !26;
foo.c:11:3
As seen, a DBG_VALUE referring to the spill stack slot is emitted before the
spill is performed.
I guess that the ideal output would be a DBG_VALUE referring to $r3 after the
MULLW, and one after the spill, i.e.:
renamable $r3 = MULLW renamable $r4, renamable $r3, implicit killed
$x3, implicit killed $x4, debug-location !18; foo.c:9:13
DBG_VALUE debug-use $r3, debug-use $noreg, !"c", !DIExpression(),
debug-location !19; foo.c:9:7 line no:9
STW killed renamable $r3, 0, %stack.0 :: (store 4 into %stack.0)
DBG_VALUE %stack.0, 0, !"c", !DIExpression(), debug-location !19;
foo.c:9:7 line no:9
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