[llvm] [Mips] Optimize instr `slti+mfc1+cvt.s.d` to `slti+mfhc1` (PR #187463)

[via llvm-commits]

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+; RUN: llc -mtriple=mipsel-unknown-linux-gnu -mcpu=mips32 -verify-machineinstrs < %s | FileCheck %s -check-prefix=MIPS32
+
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yingopq wrote:

Have changed to mips32r2, please help review.

https://github.com/llvm/llvm-project/pull/187463