[llvm-bugs] [Bug 50083] New: RISC-V: llvm.fptosi.sat.i32.f32 doesn't work with the +f feature

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50083

            Bug ID: 50083
           Summary: RISC-V: llvm.fptosi.sat.i32.f32 doesn't work with the
                    +f feature
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: RISC-V
          Assignee: unassignedbugs at nondot.org
          Reporter: alex at crichton.co
                CC: asb at lowrisc.org, llvm-bugs at lists.llvm.org

The Rust compiler recently tried to update --
https://github.com/rust-lang/rust/pull/84339 -- 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 https://bugs.llvm.org/ 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'

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