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intel/fs: Handle source modifiers in lower_integer_multiplication().

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lower_integer_multiplication() implements 32x32-bit multiplication on
some platforms by bit-casting one of the 32-bit sources into two
16-bit unsigned integer portions.  This can give incorrect results if
the original instruction specified a source modifier.  Fix it by
emitting an additional MOV instruction implementing the source
modifiers where necessary.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
This commit is contained in:
Francisco Jerez
2018-12-29 01:44:00 -08:00
parent 0206ffc28d
commit c5f9c0009d
2 changed files with 37 additions and 2 deletions
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src/intel/compiler/brw_fs.cpp
+18 -2
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@@ -3862,6 +3862,9 @@ fs_visitor::lower_integer_multiplication()
high.offset = inst->dst.offset % REG_SIZE;
if (devinfo->gen >= 7) {
if (inst->src[1].abs)
lower_src_modifiers(this, block, inst, 1);
if (inst->src[1].file == IMM) {
ibld.MUL(low, inst->src[0],
brw_imm_uw(inst->src[1].ud & 0xffff));
@@ -3874,6 +3877,9 @@ fs_visitor::lower_integer_multiplication()
subscript(inst->src[1], BRW_REGISTER_TYPE_UW, 1));
}
} else {
if (inst->src[0].abs)
lower_src_modifiers(this, block, inst, 0);
ibld.MUL(low, subscript(inst->src[0], BRW_REGISTER_TYPE_UW, 0),
inst->src[1]);
ibld.MUL(high, subscript(inst->src[0], BRW_REGISTER_TYPE_UW, 1),
@@ -3891,6 +3897,18 @@ fs_visitor::lower_integer_multiplication()
}
} else if (inst->opcode == SHADER_OPCODE_MULH) {
/* According to the BDW+ BSpec page for the "Multiply Accumulate
* High" instruction:
*
* "An added preliminary mov is required for source modification on
* src1:
* mov (8) r3.0<1>:d -r3<8;8,1>:d
* mul (8) acc0:d r2.0<8;8,1>:d r3.0<16;8,2>:uw
* mach (8) r5.0<1>:d r2.0<8;8,1>:d r3.0<8;8,1>:d"
*/
if (devinfo->gen >= 8 && (inst->src[1].negate || inst->src[1].abs))
lower_src_modifiers(this, block, inst, 1);
/* Should have been lowered to 8-wide. */
assert(inst->exec_size <= get_lowered_simd_width(devinfo, inst));
const fs_reg acc = retype(brw_acc_reg(inst->exec_size),
@@ -3906,8 +3924,6 @@ fs_visitor::lower_integer_multiplication()
* On Gen8, the multiply instruction does a full 32x32-bit
* multiply, but in order to do a 64-bit multiply we can simulate
* the previous behavior and then use a MACH instruction.
*
* FINISHME: Don't use source modifiers on src1.
*/
assert(mul->src[1].type == BRW_REGISTER_TYPE_D ||
mul->src[1].type == BRW_REGISTER_TYPE_UD);