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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - phi inserted before landingpad by GCOVProfiling causes incorrect code generation"
href="https://bugs.llvm.org/show_bug.cgi?id=45261">45261</a>
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<th>Summary</th>
<td>phi inserted before landingpad by GCOVProfiling causes incorrect code generation
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>9.0
</td>
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<tr>
<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Common Code Generator Code
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>amanieu@gmail.com
</td>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<pre>Created <span class=""><a href="attachment.cgi?id=23265" name="attach_23265" title="IR of the function with the bug">attachment 23265</a> <a href="attachment.cgi?id=23265&action=edit" title="IR of the function with the bug">[details]</a></span>
IR of the function with the bug
Upstream bug: <a href="https://github.com/rust-lang/rust/issues/70148">https://github.com/rust-lang/rust/issues/70148</a>
rustc has a -Zprofile option which uses the "insert-gcov-profiling" LLVM pass
to insert profiling instrumentation to a program.
This pass generates the following IR for landing pads:
catch.i: ; preds = %.noexc
%120 = phi i64* [ getelementptr inbounds ([24 x i64], [24 x i64]*
@__llvm_gcov_ctr.27, i64 0, i64 11), %.noexc ]
%121 = landingpad { i8*, i32 }
catch i8* null
%122 = load i64, i64* %120
%123 = add i64 %122, 1
store i64 %123, i64* %120
Which is then lowered (with llc -O0) to this:
.LBB0_14: # %catch.i
movq 160(%rsp), %rcx # 8-byte Reload
movl $1, %esi
.Ltmp2:
movabsq $__llvm_gcov_ctr.27, %rdi
addq $120, %rdi
movq (%rcx), %r8
addq $1, %r8
movq %r8, (%rcx)
The unwinding data points to .Ltmp2 as the landing pad address, and .LBB0_14 is
unreachable. This results in %rcx being left uninitialized in the landing pad.</pre>
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