Port some intrinsic lowering code from LLVM/C++. #452
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maleadt
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| Float64 | ||
| else | ||
| error("Unsupported maximum/minimum type: $typ") | ||
| end | ||
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| # create a function that performs the IEEE-compliant operation. | ||
| # normally we'd do this inline, but LLVM.jl doesn't have BB split functionality. | ||
| new_intr_fn = "air.minimum.f$(8*sizeof(jltyp))" | ||
| if haskey(functions(mod), new_intr_fn) | ||
| new_intr = functions(mod)[new_intr_fn] | ||
| else | ||
| new_intr = LLVM.Function(mod, new_intr_fn, LLVM.FunctionType(typ, parameters(call_ft))) | ||
| push!(function_attributes(new_intr), EnumAttribute("alwaysinline"; ctx)) | ||
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| arg0, arg1 = parameters(new_intr) | ||
| @assert value_type(arg0) == value_type(arg1) | ||
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| bb_check_arg0 = BasicBlock(new_intr, "check_arg0"; ctx) | ||
| bb_nan_arg0 = BasicBlock(new_intr, "nan_arg0"; ctx) | ||
| bb_check_arg1 = BasicBlock(new_intr, "check_arg1"; ctx) | ||
| bb_nan_arg1 = BasicBlock(new_intr, "nan_arg1"; ctx) | ||
| bb_check_zero = BasicBlock(new_intr, "check_zero"; ctx) | ||
| bb_compare_zero = BasicBlock(new_intr, "compare_zero"; ctx) | ||
| bb_fallback = BasicBlock(new_intr, "fallback"; ctx) | ||
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| @dispose builder=IRBuilder(ctx) begin | ||
| # first, check if either argument is NaN, and return it if so | ||
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| position!(builder, bb_check_arg0) | ||
| arg0_nan = fcmp!(builder, LLVM.API.LLVMRealUNO, arg0, arg0) | ||
| br!(builder, arg0_nan, bb_nan_arg0, bb_check_arg1) | ||
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| position!(builder, bb_nan_arg0) | ||
| ret!(builder, arg0) | ||
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| position!(builder, bb_check_arg1) | ||
| arg1_nan = fcmp!(builder, LLVM.API.LLVMRealUNO, arg1, arg1) | ||
| br!(builder, arg1_nan, bb_nan_arg1, bb_check_zero) | ||
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| position!(builder, bb_nan_arg1) | ||
| ret!(builder, arg1) | ||
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| # then, check if both arguments are zero and have a mismatching sign. | ||
| # if so, return in accordance to the intrinsic (minimum or maximum) | ||
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| position!(builder, bb_check_zero) | ||
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| typ′ = LLVM.IntType(8*sizeof(jltyp); ctx) | ||
| arg0′ = bitcast!(builder, arg0, typ′) | ||
| arg1′ = bitcast!(builder, arg1, typ′) | ||
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| arg0_zero = fcmp!(builder, LLVM.API.LLVMRealUEQ, arg0, | ||
| LLVM.ConstantFP(typ, zero(jltyp))) | ||
| arg1_zero = fcmp!(builder, LLVM.API.LLVMRealUEQ, arg1, | ||
| LLVM.ConstantFP(typ, zero(jltyp))) | ||
| args_zero = and!(builder, arg0_zero, arg1_zero) | ||
| arg0_sign = and!(builder, arg0′, LLVM.ConstantInt(typ′, Base.sign_mask(jltyp))) | ||
| arg1_sign = and!(builder, arg1′, LLVM.ConstantInt(typ′, Base.sign_mask(jltyp))) | ||
| sign_mismatch = icmp!(builder, LLVM.API.LLVMIntNE, arg0_sign, arg1_sign) | ||
| relevant_zero = and!(builder, args_zero, sign_mismatch) | ||
| br!(builder, relevant_zero, bb_compare_zero, bb_fallback) | ||
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| position!(builder, bb_compare_zero) | ||
| arg0_negative = icmp!(builder, LLVM.API.LLVMIntNE, arg0_sign, | ||
| LLVM.ConstantInt(typ′, 0)) | ||
| val = if intr == LLVM.Intrinsic("llvm.minimum") | ||
| select!(builder, arg0_negative, arg0, arg1) | ||
| else | ||
| select!(builder, arg0_negative, arg1, arg0) | ||
| end | ||
| ret!(builder, val) | ||
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| # finally, it's safe to use the existing minnum/maxnum intrinsics | ||
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| position!(builder, bb_fallback) | ||
| fallback_intr_fn = if intr == LLVM.Intrinsic("llvm.minimum") | ||
| "air.fmin.f$(8*sizeof(jltyp))" | ||
| else | ||
| "air.fmax.f$(8*sizeof(jltyp))" | ||
| end | ||
| fallback_intr = if haskey(functions(mod), fallback_intr_fn) | ||
| functions(mod)[fallback_intr_fn] | ||
| else | ||
| LLVM.Function(mod, fallback_intr_fn, LLVM.FunctionType(typ, parameters(call_ft))) | ||
| end | ||
| val = call!(builder, fallback_intr, collect(parameters(new_intr))) | ||
| ret!(builder, val) | ||
| end | ||
| end | ||
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| @dispose builder=IRBuilder(ctx) begin | ||
| position!(builder, call) | ||
| debuglocation!(builder, call) | ||
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| new_value = call!(builder, new_intr, arguments(call)) | ||
| replace_uses!(call, new_value) | ||
| unsafe_delete!(bb, call) | ||
| changed = true | ||
| end | ||
| end |
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@gbaraldi Look what you made me do.
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Sorry :(. It's very annoying that backends don't know how to lower this.
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No problem 🙂 But yeah it is annoying that you can't reasonably expect fairly basic things to be available across all back-ends; it should be easy enough for LLVM to provide a fallback lowering...
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X86 not having a lowering is telling though.
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I'm hoping to make the LLVM back-end more generic, focussing on only the IR downgrade part (which could be used by other back-ends too, e.g., to target NVVM).
This PR also includes a fix, now properly attaching AIR intrinsic metadata where we didn't before. As a result, it'll break some broken tests in Metal.jl, which I'll fix after this is merged.