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[druntime] core.int128: Don't support/test invalid shift-by values >= 128

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This enables using (LLVM/gcc) intrinsics for shifts, for which such
inputs are undefined behavior, as for builtin types.
This commit is contained in:
Martin Kinkelin 2025-03-24 01:11:14 +01:00 • committed by Nicholas Wilson
parent f4da0efbd2
commit ea4b1e9607
1 changed files with 10 additions and 17 deletions
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27
druntime/src/core/int128.d
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@ -189,10 +189,8 @@ Cent sar1(Cent c)
*/ */
pure pure
Cent shl(Cent c, uint n) Cent shl(Cent c, uint n)
in (n < Ubits * 2)
{ {
if (n >= Ubits * 2)
return Zero;
if (n >= Ubits) if (n >= Ubits)
{ {
c.hi = c.lo << (n - Ubits); c.hi = c.lo << (n - Ubits);
@ -216,10 +214,8 @@ Cent shl(Cent c, uint n)
*/ */
pure pure
Cent shr(Cent c, uint n) Cent shr(Cent c, uint n)
in (n < Ubits * 2)
{ {
if (n >= Ubits * 2)
return Zero;
if (n >= Ubits) if (n >= Ubits)
{ {
c.lo = c.hi >> (n - Ubits); c.lo = c.hi >> (n - Ubits);
@ -243,18 +239,13 @@ Cent shr(Cent c, uint n)
*/ */
pure pure
Cent sar(Cent c, uint n) Cent sar(Cent c, uint n)
in (n < Ubits * 2)
{ {
const signmask = -(c.hi >> (Ubits - 1)); const signmask = -(c.hi >> (Ubits - 1));
const signshift = (Ubits * 2) - n; const signshift = (Ubits * 2) - n;
c = shr(c, n); c = shr(c, n);
// Sign extend all bits beyond the precision of Cent. if (signshift == Ubits * 2)
if (n >= Ubits * 2)
{
c.hi = signmask;
c.lo = signmask;
}
else if (signshift >= Ubits * 2)
{ {
} }
else if (signshift >= Ubits) else if (signshift >= Ubits)
@ -317,6 +308,8 @@ pure
Cent rol(Cent c, uint n) Cent rol(Cent c, uint n)
{ {
n &= Ubits * 2 - 1; n &= Ubits * 2 - 1;
if (n == 0)
return c;
Cent l = shl(c, n); Cent l = shl(c, n);
Cent r = shr(c, Ubits * 2 - n); Cent r = shr(c, Ubits * 2 - n);
return or(l, r); return or(l, r);
@ -334,6 +327,8 @@ pure
Cent ror(Cent c, uint n) Cent ror(Cent c, uint n)
{ {
n &= Ubits * 2 - 1; n &= Ubits * 2 - 1;
if (n == 0)
return c;
Cent r = shr(c, n); Cent r = shr(c, n);
Cent l = shl(c, Ubits * 2 - n); Cent l = shl(c, Ubits * 2 - n);
return or(r, l); return or(r, l);
@ -893,18 +888,14 @@ unittest
assert(shl(C10,0) == C10); assert(shl(C10,0) == C10);
assert(shl(C10,Ubits) == C10_0); assert(shl(C10,Ubits) == C10_0);
assert(shl(C10,1) == C20); assert(shl(C10,1) == C20);
assert(shl(C10,Ubits * 2) == C0);
assert(shr(C10_0,0) == C10_0); assert(shr(C10_0,0) == C10_0);
assert(shr(C10_0,Ubits) == C10); assert(shr(C10_0,Ubits) == C10);
assert(shr(C10_0,Ubits - 1) == C20); assert(shr(C10_0,Ubits - 1) == C20);
assert(shr(C10_0,Ubits + 1) == C5); assert(shr(C10_0,Ubits + 1) == C5);
assert(shr(C10_0,Ubits * 2) == C0);
assert(sar(C10_0,0) == C10_0); assert(sar(C10_0,0) == C10_0);
assert(sar(C10_0,Ubits) == C10); assert(sar(C10_0,Ubits) == C10);
assert(sar(C10_0,Ubits - 1) == C20); assert(sar(C10_0,Ubits - 1) == C20);
assert(sar(C10_0,Ubits + 1) == C5); assert(sar(C10_0,Ubits + 1) == C5);
assert(sar(C10_0,Ubits * 2) == C0);
assert(sar(Cm1,Ubits * 2) == Cm1);
assert(shl1(C10) == C20); assert(shl1(C10) == C20);
assert(shr1(C10_0) == C5_0); assert(shr1(C10_0) == C5_0);
@ -961,4 +952,6 @@ unittest
assert(rol(ror(C7_9, 5), 5) == C7_9); assert(rol(ror(C7_9, 5), 5) == C7_9);
assert(rol(C7_9, 1) == rol1(C7_9)); assert(rol(C7_9, 1) == rol1(C7_9));
assert(ror(C7_9, 1) == ror1(C7_9)); assert(ror(C7_9, 1) == ror1(C7_9));
assert(rol(C7_9, 0) == C7_9);
assert(ror(C7_9, 0) == C7_9);
} }