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nir/int64: Properly handle imod/irem

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The previous implementation was fine for GLSL which doesn't really have
a signed modulus/remainder.  They just leave the behavior undefined
whenever either source is negative.  However, in SPIR-V, there is a
defined behavior for negative arguments.  This commit beefs up the pass
so that it handles both correctly.  Tested using a hacked up version of
the Vulkan CTS test to get 64-bit support.

Reviewed-by: Matt Turner <mattst88@gmail.com>
This commit is contained in:
Jason Ekstrand
2017-03-01 15:20:31 -08:00
parent 9745bef308
commit bc456749bd
1 changed files with 21 additions and 3 deletions
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24
src/compiler/nir/nir_lower_int64.c
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@@ -179,12 +179,28 @@ lower_imod64(nir_builder *b, nir_ssa_def *n, nir_ssa_def *d)
{
nir_ssa_def *n_hi = nir_unpack_64_2x32_split_y(b, n);
nir_ssa_def *d_hi = nir_unpack_64_2x32_split_y(b, d);
nir_ssa_def *n_is_neg = nir_ilt(b, n_hi, nir_imm_int(b, 0));
nir_ssa_def *d_is_neg = nir_ilt(b, d_hi, nir_imm_int(b, 0));
nir_ssa_def *negate = nir_ine(b, nir_ilt(b, n_hi, nir_imm_int(b, 0)),
nir_ilt(b, d_hi, nir_imm_int(b, 0)));
nir_ssa_def *q, *r;
lower_udiv64_mod64(b, nir_iabs(b, n), nir_iabs(b, d), &q, &r);
return nir_bcsel(b, negate, nir_ineg(b, r), r);
nir_ssa_def *rem = nir_bcsel(b, n_is_neg, nir_ineg(b, r), r);
return nir_bcsel(b, nir_ieq(b, r, nir_imm_int64(b, 0)), nir_imm_int64(b, 0),
nir_bcsel(b, nir_ieq(b, n_is_neg, d_is_neg), rem,
nir_iadd(b, rem, d)));
}
static nir_ssa_def *
lower_irem64(nir_builder *b, nir_ssa_def *n, nir_ssa_def *d)
{
nir_ssa_def *n_hi = nir_unpack_64_2x32_split_y(b, n);
nir_ssa_def *n_is_neg = nir_ilt(b, n_hi, nir_imm_int(b, 0));
nir_ssa_def *q, *r;
lower_udiv64_mod64(b, nir_iabs(b, n), nir_iabs(b, d), &q, &r);
return nir_bcsel(b, n_is_neg, nir_ineg(b, r), r);
}
static nir_lower_int64_options
@@ -226,6 +242,8 @@ lower_int64_alu_instr(nir_builder *b, nir_alu_instr *alu)
return lower_umod64(b, src[0], src[1]);
case nir_op_imod:
return lower_imod64(b, src[0], src[1]);
case nir_op_irem:
return lower_irem64(b, src[0], src[1]);
default:
unreachable("Invalid ALU opcode to lower");
}