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Fix sign extend #155

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Fix sign extend #155

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0082adf
C23 runtime: fix Sign_Extend
alastairreid Aug 19, 2026
997f346
AC runtime: fix Sign_Extend
alastairreid Aug 19, 2026
d196d78
C23/AC runtimes: test for Sign_Extend fix
alastairreid Aug 19, 2026
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3 changes: 2 additions & 1 deletion libISA/runtime_ac.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -580,8 +580,9 @@ module Runtime : RT.RuntimeLib = struct
RT.pp_expr x

let zero_extend_bits (fmt : PP.formatter) (m : int) (n : int) (x : RT.rt_expr) : unit =
PP.fprintf fmt "((%a)%a)"
PP.fprintf fmt "((%a)(%a)%a)"
ty_bits n
ty_bits m
RT.pp_expr x

let sign_extend_bits (fmt : PP.formatter) (m : int) (n : int) (x : RT.rt_expr) : unit =
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3 changes: 2 additions & 1 deletion libISA/runtime_c23.ml
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Expand Up @@ -499,8 +499,9 @@ module Runtime : RT.RuntimeLib = struct
RT.pp_expr y

let zero_extend_bits (fmt : PP.formatter) (m : int) (n : int) (x : RT.rt_expr) : unit =
PP.fprintf fmt "((%a)%a)"
PP.fprintf fmt "((%a)(%a)%a)"
ty_uint n
ty_uint m

@nikolaykosarev nikolaykosarev Aug 24, 2026

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Would be good to skip this cast when n = m, to reduce the size of generated code.

RT.pp_expr x

let sign_extend_bits (fmt : PP.formatter) (m : int) (n : int) (x : RT.rt_expr) : unit =
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15 changes: 15 additions & 0 deletions tests/backends/bits_zext_01.isa
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@@ -0,0 +1,15 @@
// RUN: %aslrun %s | filecheck %s
// Copyright (C) 2023-2026 Intel Corporation

// This reproduces an actual bug found in a spec
function Test(x : Bits(8)) -> Bits(64)
begin
return Std::Bits::Zero_Extend(not x, 64);
end

function main() -> Builtin::Foreign::CInt
begin
Std::Print::Bits::Hex(Test(0x87)); Print("\n");
// CHECK: 64'x78
return Builtin::Foreign::CInt::From_Integer(0);
end