104 lines
2.7 KiB
LLVM
104 lines
2.7 KiB
LLVM
;*******************************************************************************
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; Convert fp32 in IEEE 32-bit floating-point format to truncated signed integer.
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;
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define i64 @fp32_to_int(i64 %fp32) {
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%neg = alloca i1 ; sign bit of fp32
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%bits = alloca i64 ; bits of fp32 without the sign bit
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%exp = alloca i64 ; expoent
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%int = alloca i64 ; integer part of fp32
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%nbits = alloca i64 ; number of bits after the dot if 2^exp is applied
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%fract = alloca i64 ; mantissa of fp32
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; neg = fp32 & 0x80000000
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%1 = and i64 %fp32, 2147483648 ; 0x80000000
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%2 = icmp ne i64 %1, 0
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store i1 %2, i1* %neg
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; bits = fp32 & 0x7FFFFFFF
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%3 = and i64 %fp32, 2147483647 ; 0x7FFFFFFF
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store i64 %3, i64* %bits
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; exp = bits >> 23
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%4 = load i64, i64* %bits
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%5 = lshr i64 %4, 23
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store i64 %5, i64* %exp
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; exp -= 127
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%6 = load i64, i64* %exp
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%7 = sub i64 %6, 127
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store i64 %7, i64* %exp
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; int = 0
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store i64 0, i64* %int
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; bits > 0
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%8 = load i64, i64* %bits
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%9 = icmp sgt i64 %8, 0
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br i1 %9, label %check_exponent, label %check_sign
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check_exponent: ; preds = %1
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; exp >= 0
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%10 = load i64, i64* %exp
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%11 = icmp sge i64 %10, 0
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br i1 %11, label %compute, label %check_sign
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compute: ; preds = %check_exponent
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; nbits = 23 - exp
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%12 = load i64, i64* %exp
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%13 = sub i64 23, %12
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store i64 %13, i64* %nbits
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; fract = bits & 0x7FFFFF
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%14 = load i64, i64* %bits
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%15 = and i64 %14, 8388607 ; 0x7FFFFF
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store i64 %15, i64* %fract
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; fract |= 0x800000
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%16 = load i64, i64* %fract
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%17 = or i64 %16, 8388608 ; 0x800000
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store i64 %17, i64* %fract
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; nbits > 0
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%18 = load i64, i64* %nbits
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%19 = icmp sgt i64 %18, 0
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br i1 %19, label %shift_right, label %shift_left
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shift_right: ; preds = %compute
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; int = fract >> nbits
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%20 = load i64, i64* %fract
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%21 = load i64, i64* %nbits
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%22 = lshr i64 %20, %21
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store i64 %22, i64* %int
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br label %check_sign
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shift_left: ; preds = %compute
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; int = fraction << -nbits
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%23 = load i64, i64* %fract
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%24 = load i64, i64* %nbits
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%25 = sub i64 0, %24
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%26 = shl i64 %23, %25
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store i64 %26, i64* %int
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br label %check_sign
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check_sign: ; preds = %shift_left, %shift_right, %check_exponent, %1
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; neg > 0
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%27 = load i1, i1* %neg
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br i1 %27, label %negate, label %return
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negate: ; preds = %check_sign
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; int = -int
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%28 = load i64, i64* %int
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%29 = sub i64 0, %28
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store i64 %29, i64* %int
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br label %return
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return: ; preds = %negate, %check_sign
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; return int
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%30 = load i64, i64* %int
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ret i64 %30
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}
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define i64 @main(i64 %argc, i8** %argv) {
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%int = call i64 @fp32_to_int(i64 1132389990) ; 0x437EE666: 254.9
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ret i64 %int
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}
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