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For _Float16 type, add insn and expanders to optimize x / y to x * rcp (y), and x / sqrt (y) to x * rsqrt (y). As Half float only have minor precision difference between div and mul * rcp, there is no need for Newton-Rhapson approximation. gcc/ChangeLog: * config/i386/i386.c (use_rsqrt_p): Add mode parameter, enable HFmode rsqrt without TARGET_SSE_MATH. (ix86_optab_supported_p): Refactor rint, adjust floor, ceil, btrunc condition to be restricted by -ftrapping-math, adjust use_rsqrt_p function call. * config/i386/i386.md (rcphf2): New define_insn. (rsqrthf2): Likewise. * config/i386/sse.md (div<mode>3): Change VF2H to VF2. (div<mode>3): New expander for HF mode. (rsqrt<mode>2): Likewise. (*avx512fp16_vmrcpv8hf2): New define_insn for rpad pass. (*avx512fp16_vmrsqrtv8hf2): Likewise. gcc/testsuite/ChangeLog: * gcc.target/i386/avx512fp16-recip-1.c: New test. * gcc.target/i386/avx512fp16-recip-2.c: Ditto. * gcc.target/i386/pr102464.c: Add -fno-trapping-math.
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