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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [DebugInfo] Undef DBG_VALUE is emitted for float parameter passed on the stack"
href="https://bugs.llvm.org/show_bug.cgi?id=40777">40777</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[DebugInfo] Undef DBG_VALUE is emitted for float parameter passed on the stack
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>DebugInfo
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david.stenberg@ericsson.com
</td>
</tr>
<tr>
<th>CC</th>
<td>jdevlieghere@apple.com, keith.walker@arm.com, llvm-bugs@lists.llvm.org, paul_robinson@playstation.sony.com
</td>
</tr></table>
<p>
<div>
<pre>On r353941, if you compile the following code with `--target=arm -O1 -g':
float fn1(int p1, int p2, int p3, int p4, float p5) {
return p5;
}
no non-undef location is emitted for p5:
fn1:
.Lfunc_begin0:
.file 1 "/path/to/repo" "float.c"
.loc 1 1 0 @ float.c:1:0
.fnstart
.cfi_sections .debug_frame
.cfi_startproc
@ %bb.0: @ %entry
@DEBUG_VALUE: fn1:p1 <- $r0
@DEBUG_VALUE: fn1:p2 <- $r1
@DEBUG_VALUE: fn1:p3 <- $r2
@DEBUG_VALUE: fn1:p4 <- $r3
ldr r0, [sp]
.Ltmp0:
@DEBUG_VALUE: fn1:p5 <- undef <------------------------
llvm-dwarfdump output:
0x00000071: DW_TAG_formal_parameter
DW_AT_name ("p5")
DW_AT_decl_file ("/path/to/repo/float.c")
DW_AT_decl_line (1)
DW_AT_type (0x0000007d "float")
llc -debug output:
*** IR Dump After Module Verifier ***
; Function Attrs: norecurse nounwind readnone
define dso_local arm_aapcscc float @fn1(i32 %p1, i32 %p2, i32 %p3, i32 %p4,
float returned %p5) local_unnamed_addr #0 !dbg !8 {
entry:
call void @llvm.dbg.value(metadata i32 %p1, metadata !14, metadata
!DIExpression()), !dbg !19
call void @llvm.dbg.value(metadata i32 %p2, metadata !15, metadata
!DIExpression()), !dbg !20
call void @llvm.dbg.value(metadata i32 %p3, metadata !16, metadata
!DIExpression()), !dbg !21
call void @llvm.dbg.value(metadata i32 %p4, metadata !17, metadata
!DIExpression()), !dbg !22
call void @llvm.dbg.value(metadata float %p5, metadata !18, metadata
!DIExpression()), !dbg !23
ret float %p5, !dbg !24
}
# *** IR Dump Before ARM Instruction Selection ***:
# Machine code for function fn1: IsSSA, TracksLiveness
# End machine code for function fn1.
# *** IR Dump After ARM Instruction Selection ***:
# Machine code for function fn1: IsSSA, TracksLiveness
Frame Objects:
fi#-1: size=4, align=8, fixed, at location [SP]
bb.0.entry:
DBG_VALUE $r0, $noreg, !"p1", !DIExpression(), debug-location !19;
float.c:1:15 line no:1
DBG_VALUE $r1, $noreg, !"p2", !DIExpression(), debug-location !20;
float.c:1:23 line no:1
DBG_VALUE $r2, $noreg, !"p3", !DIExpression(), debug-location !21;
float.c:1:31 line no:1
DBG_VALUE $r3, $noreg, !"p4", !DIExpression(), debug-location !22;
float.c:1:39 line no:1
%4:gpr = LDRi12 %fixed-stack.0, 0, 14, $noreg :: (load 4 from
%fixed-stack.0, align 8)
DBG_VALUE $noreg, $noreg, !"p5", !DIExpression(), debug-location !23;
float.c:1:49 line no:1
$r0 = COPY %4:gpr, debug-location !24; float.c:2:3
BX_RET 14, $noreg, implicit $r0, debug-location !24; float.c:2:3
# End machine code for function fn1.
If you instead change p5 to an int, a FI-referencing debug value is inserted
for the parameter at the start of the function. That DBG_VALUE is produced by
the following code in EmitFuncArgumentDbgValue():
if (!Op && N.getNode())
// Check if frame index is available.
if (LoadSDNode *LNode = dyn_cast<LoadSDNode>(N.getNode()))
if (FrameIndexSDNode *FINode =
dyn_cast<FrameIndexSDNode>(LNode->getBasePtr().getNode()))
Op = MachineOperand::CreateFI(FINode->getIndex());
However, in the case of the float parameter, the LoadSDNode is wrapped by a
bitcast, resulting in that code not triggering.</pre>
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