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glsl: Add lowering pass for ir_bin_imul_high

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This isn't the lowering pass you want.  Most GPUs that can support GLSL
1.30 have a multiply unit that can do something more interesting than
32x32->32.  Many have 32x16->48.  Any GPU that does, should do the
lowering in the backend.  This is just the thing that will always work.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
This commit is contained in:
Ian Romanick
2016-06-27 15:21:21 -07:00
parent 1b5477668a
commit a2379e44aa
2 changed files with 150 additions and 0 deletions
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1
src/compiler/glsl/ir_optimization.h
View File

@@ -48,6 +48,7 @@
#define REVERSE_TO_SHIFTS 0x10000
#define FIND_LSB_TO_FLOAT_CAST 0x20000
#define FIND_MSB_TO_FLOAT_CAST 0x40000
#define IMUL_HIGH_TO_MUL 0x80000
/**
* \see class lower_packing_builtins_visitor

149
src/compiler/glsl/lower_instructions.cpp
View File

@@ -165,6 +165,7 @@ private:
void reverse_to_shifts(ir_expression *ir);
void find_lsb_to_float_cast(ir_expression *ir);
void find_msb_to_float_cast(ir_expression *ir);
void imul_high_to_mul(ir_expression *ir);
};
} /* anonymous namespace */
@@ -1412,6 +1413,149 @@ lower_instructions_visitor::find_msb_to_float_cast(ir_expression *ir)
this->progress = true;
}
void
lower_instructions_visitor::imul_high_to_mul(ir_expression *ir)
{
/* ABCD
* * EFGH
* ======
* (GH * CD) + (GH * AB) << 16 + (EF * CD) << 16 + (EF * AB) << 32
*
* In GLSL, (a * b) becomes
*
* uint m1 = (a & 0x0000ffffu) * (b & 0x0000ffffu);
* uint m2 = (a & 0x0000ffffu) * (b >> 16);
* uint m3 = (a >> 16) * (b & 0x0000ffffu);
* uint m4 = (a >> 16) * (b >> 16);
*
* uint c1;
* uint c2;
* uint lo_result;
* uint hi_result;
*
* lo_result = uaddCarry(m1, m2 << 16, c1);
* hi_result = m4 + c1;
* lo_result = uaddCarry(lo_result, m3 << 16, c2);
* hi_result = hi_result + c2;
* hi_result = hi_result + (m2 >> 16) + (m3 >> 16);
*/
const unsigned elements = ir->operands[0]->type->vector_elements;
ir_variable *src1 =
new(ir) ir_variable(glsl_type::uvec(elements), "src1", ir_var_temporary);
ir_variable *src1h =
new(ir) ir_variable(glsl_type::uvec(elements), "src1h", ir_var_temporary);
ir_variable *src1l =
new(ir) ir_variable(glsl_type::uvec(elements), "src1l", ir_var_temporary);
ir_variable *src2 =
new(ir) ir_variable(glsl_type::uvec(elements), "src2", ir_var_temporary);
ir_variable *src2h =
new(ir) ir_variable(glsl_type::uvec(elements), "src2h", ir_var_temporary);
ir_variable *src2l =
new(ir) ir_variable(glsl_type::uvec(elements), "src2l", ir_var_temporary);
ir_variable *t1 =
new(ir) ir_variable(glsl_type::uvec(elements), "t1", ir_var_temporary);
ir_variable *t2 =
new(ir) ir_variable(glsl_type::uvec(elements), "t2", ir_var_temporary);
ir_variable *lo =
new(ir) ir_variable(glsl_type::uvec(elements), "lo", ir_var_temporary);
ir_variable *hi =
new(ir) ir_variable(glsl_type::uvec(elements), "hi", ir_var_temporary);
ir_variable *different_signs = NULL;
ir_constant *c0000FFFF = new(ir) ir_constant(0x0000FFFFu, elements);
ir_constant *c16 = new(ir) ir_constant(16u, elements);
ir_instruction &i = *base_ir;
i.insert_before(src1);
i.insert_before(src2);
i.insert_before(src1h);
i.insert_before(src2h);
i.insert_before(src1l);
i.insert_before(src2l);
if (ir->operands[0]->type->base_type == GLSL_TYPE_UINT) {
i.insert_before(assign(src1, ir->operands[0]));
i.insert_before(assign(src2, ir->operands[1]));
} else {
assert(ir->operands[0]->type->base_type == GLSL_TYPE_INT);
ir_variable *itmp1 =
new(ir) ir_variable(glsl_type::ivec(elements), "itmp1", ir_var_temporary);
ir_variable *itmp2 =
new(ir) ir_variable(glsl_type::ivec(elements), "itmp2", ir_var_temporary);
ir_constant *c0 = new(ir) ir_constant(int(0), elements);
i.insert_before(itmp1);
i.insert_before(itmp2);
i.insert_before(assign(itmp1, ir->operands[0]));
i.insert_before(assign(itmp2, ir->operands[1]));
different_signs =
new(ir) ir_variable(glsl_type::bvec(elements), "different_signs",
ir_var_temporary);
i.insert_before(different_signs);
i.insert_before(assign(different_signs, expr(ir_binop_logic_xor,
less(itmp1, c0),
less(itmp2, c0->clone(ir, NULL)))));
i.insert_before(assign(src1, i2u(abs(itmp1))));
i.insert_before(assign(src2, i2u(abs(itmp2))));
}
i.insert_before(assign(src1l, bit_and(src1, c0000FFFF)));
i.insert_before(assign(src2l, bit_and(src2, c0000FFFF->clone(ir, NULL))));
i.insert_before(assign(src1h, rshift(src1, c16)));
i.insert_before(assign(src2h, rshift(src2, c16->clone(ir, NULL))));
i.insert_before(lo);
i.insert_before(hi);
i.insert_before(t1);
i.insert_before(t2);
i.insert_before(assign(lo, mul(src1l, src2l)));
i.insert_before(assign(t1, mul(src1l, src2h)));
i.insert_before(assign(t2, mul(src1h, src2l)));
i.insert_before(assign(hi, mul(src1h, src2h)));
i.insert_before(assign(hi, add(hi, carry(lo, lshift(t1, c16->clone(ir, NULL))))));
i.insert_before(assign(lo, add(lo, lshift(t1, c16->clone(ir, NULL)))));
i.insert_before(assign(hi, add(hi, carry(lo, lshift(t2, c16->clone(ir, NULL))))));
i.insert_before(assign(lo, add(lo, lshift(t2, c16->clone(ir, NULL)))));
if (different_signs == NULL) {
assert(ir->operands[0]->type->base_type == GLSL_TYPE_UINT);
ir->operation = ir_binop_add;
ir->operands[0] = add(hi, rshift(t1, c16->clone(ir, NULL)));
ir->operands[1] = rshift(t2, c16->clone(ir, NULL));
} else {
assert(ir->operands[0]->type->base_type == GLSL_TYPE_INT);
i.insert_before(assign(hi, add(add(hi, rshift(t1, c16->clone(ir, NULL))),
rshift(t2, c16->clone(ir, NULL)))));
/* For channels where different_signs is set we have to perform a 64-bit
* negation. This is *not* the same as just negating the high 32-bits.
* Consider -3 * 2. The high 32-bits is 0, but the desired result is
* -1, not -0! Recall -x == ~x + 1.
*/
ir_variable *neg_hi =
new(ir) ir_variable(glsl_type::ivec(elements), "neg_hi", ir_var_temporary);
ir_constant *c1 = new(ir) ir_constant(1u, elements);
i.insert_before(neg_hi);
i.insert_before(assign(neg_hi, add(bit_not(u2i(hi)),
u2i(carry(bit_not(lo), c1)))));
ir->operation = ir_triop_csel;
ir->operands[0] = new(ir) ir_dereference_variable(different_signs);
ir->operands[1] = new(ir) ir_dereference_variable(neg_hi);
ir->operands[2] = u2i(hi);
}
}
ir_visitor_status
lower_instructions_visitor::visit_leave(ir_expression *ir)
{
@@ -1544,6 +1688,11 @@ lower_instructions_visitor::visit_leave(ir_expression *ir)
find_msb_to_float_cast(ir);
break;
case ir_binop_imul_high:
if (lowering(IMUL_HIGH_TO_MUL))
imul_high_to_mul(ir);
break;
default:
return visit_continue;
}