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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - RISC-V: llvm.fptosi.sat.i32.f32 doesn't work with the +f feature"
href="https://bugs.llvm.org/show_bug.cgi?id=50083">50083</a>
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<th>Summary</th>
<td>RISC-V: llvm.fptosi.sat.i32.f32 doesn't work with the +f feature
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Backend: RISC-V
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>alex@crichton.co
</td>
</tr>
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<th>CC</th>
<td>asb@lowrisc.org, llvm-bugs@lists.llvm.org
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</tr></table>
<p>
<div>
<pre>The Rust compiler recently tried to update --
<a href="https://github.com/rust-lang/rust/pull/84339">https://github.com/rust-lang/rust/pull/84339</a> -- to using LLVM's `fptosi` and
`fptoui` saturating intrinsics for all targets, but we found that on the RISC-V
targets with the `+f` target feature LLVM trips an assertion about being unable
to lower. Specifically this LLVM IR:
target triple = "riscv64-unknown-linux-gnu"
define i32 @foo(float %a) #0 {
start:
%0 = tail call i32 @llvm.fptosi.sat.i32.f32(float %a)
ret i32 %0
}
declare i32 @llvm.fptosi.sat.i32.f32(float)
attributes #0 = { "target-cpu"="generic-rv64" "target-features"="+f" }
yields:
PromoteIntegerOperand Op #1: t11: i64 = fp_to_sint_sat t3, Constant:i32<32>
Do not know how to promote this operator's operand!
UNREACHABLE executed at
/root/llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp:1480!
PLEASE submit a bug report to <a href="https://bugs.llvm.org/">https://bugs.llvm.org/</a> and include the crash
backtrace.
Stack dump:
0. Program arguments:
/opt/compiler-explorer/clang-assertions-trunk/bin/llc -o /app/output.s
-x86-asm-syntax=intel <source>
1. Running pass 'Function Pass Manager' on module '<source>'.
2. Running pass 'RISCV DAG->DAG Pattern Instruction Selection' on function
'@foo'</pre>
</div>
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