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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [NVPTX] byval parameters are incorrectly lowered"
href="http://llvm.org/bugs/show_bug.cgi?id=21465">21465</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[NVPTX] byval parameters are incorrectly lowered
</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>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: PTX
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>wujingyue@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The current backend treats the base address of a byval parameter as a generic
pointer. However, generic loads don't actually work with a pointer to the
parameter space. Here's a small test case to reproduce this issue:
CUDA:
struct S {
int a, b;
};
__attribute__((global)) void TakesStruct(S input, int *output) {
*output = input.b;
}
LLVM IR:
target datalayout = "e-i64:64-v16:16-v32:32-n16:32:64"
target triple = "nvptx64-unknown-unknown"
%struct.S = type { i32, i32 }
; Function Attrs: nounwind
define void @_Z11TakesStruct1SPi(%struct.S* byval nocapture readonly %input,
i32* nocapture %output) #0 {
entry:
%b = getelementptr inbounds %struct.S* %input, i64 0, i32 1
%0 = load i32* %b, align 4, !tbaa !2
store i32 %0, i32* %output, align 4, !tbaa !7
ret void
}
attributes #0 = { nounwind "less-precise-fpmad"="false"
"no-frame-pointer-elim"="false" "no-infs-fp-math"="false"
"no-nans-fp-math"="false" "stack-protector-buffer-size"="8"
"unsafe-fp-math"="false" "use-soft-float"="false" }
!nvvm.annotations = !{!0}
!llvm.ident = !{!1}
!0 = metadata !{void (%struct.S*, i32*)* @_Z11TakesStruct1SPi, metadata
!"kernel", i32 1}
!1 = metadata !{metadata !"clang version 3.6.0 (<a href="http://llvm.org/git/clang.git">http://llvm.org/git/clang.git</a>
1f064ca0a944bf0279b0d6508268a4ea0a354b8e) (<a href="http://llvm.org/git/llvm.git">http://llvm.org/git/llvm.git</a>
8744520b533617fbbd55ef12ea936961f5225cf5)"}
!2 = metadata !{metadata !3, metadata !4, i64 4}
!3 = metadata !{metadata !"_ZTS1S", metadata !4, i64 0, metadata !4, i64 4}
!4 = metadata !{metadata !"int", metadata !5, i64 0}
!5 = metadata !{metadata !"omnipotent char", metadata !6, i64 0}
!6 = metadata !{metadata !"Simple C/C++ TBAA"}
!7 = metadata !{metadata !4, metadata !4, i64 0}
PTX (sm_35):
//
// Generated by LLVM NVPTX Back-End
//
.version 3.2
.target sm_35
.address_size 64
// .globl _Z11TakesStruct1SPi
// @_Z11TakesStruct1SPi
.visible .entry _Z11TakesStruct1SPi(
.param .align 4 .b8 _Z11TakesStruct1SPi_param_0[8],
.param .u64 _Z11TakesStruct1SPi_param_1
)
{
.reg .s32 %r<2>;
.reg .s64 %rd<3>;
// BB#0: // %entry
mov.b64 %rd1, _Z11TakesStruct1SPi_param_0;
ld.param.u64 %rd2, [_Z11TakesStruct1SPi_param_1];
ld.u32 %r1, [%rd1+4];
st.u32 [%rd2], %r1;
ret;
}
The problematic instructions are:
mov.b64 %rd1, _Z11TakesStruct1SPi_param_0;
ld.u32 %r1, [%rd1+4];
The compiled kernel crashes because the ld.u32 loads from a pointer to the
parameter space.</pre>
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