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llvmpipe: Improve persepctive correction with centroid/sample interpolation

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When doing perspective correct interpolation with centroid/sample, we should
do the perspective correction wrt to the centroid/sample position - the
precalculated 1/w value however is always wrt pixel center (when we calculate
this we don't know yet what kind of interpolation we're going to use).
Refactor things a bit as well to avoid code duplication.

Reviewed-by: Brian Paul <brian.paul@broadcom.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36079>
This commit is contained in:
Roland Scheidegger
2025-07-11 18:13:35 +02:00
committed by Marge Bot
parent 483489ed1f
commit 39ccb1ddac
1 changed files with 95 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/gallium/drivers/llvmpipe/lp_bld_interp.c
+95 -54
View File
@@ -127,6 +127,39 @@ attrib_name(LLVMValueRef val, unsigned attrib, unsigned chan, const char *suffix
}
static LLVMValueRef
interp_attrib_linear(struct lp_build_interp_soa_context *bld,
unsigned attrib,
LLVMValueRef index,
LLVMValueRef pixoffx,
LLVMValueRef pixoffy)
{
struct lp_build_context *coeff_bld = &bld->coeff_bld;
struct lp_build_context *setup_bld = &bld->setup_bld;
struct gallivm_state *gallivm = coeff_bld->gallivm;
LLVMBuilderRef builder = gallivm->builder;
LLVMValueRef dadx, dady, a;
dadx = lp_build_extract_broadcast(gallivm, setup_bld->type,
coeff_bld->type, bld->dadxaos[attrib],
index);
dady = lp_build_extract_broadcast(gallivm, setup_bld->type,
coeff_bld->type, bld->dadyaos[attrib],
index);
a = lp_build_extract_broadcast(gallivm, setup_bld->type,
coeff_bld->type, bld->a0aos[attrib],
index);
/*
* a = a0 + (x * dadx + y * dady)
*/
a = lp_build_fmuladd(builder, dadx, pixoffx, a);
a = lp_build_fmuladd(builder, dady, pixoffy, a);
return a;
}
static void
calc_offsets(struct lp_build_context *coeff_bld,
unsigned quad_start_index,
@@ -335,8 +368,6 @@ attribs_update_simple(struct lp_build_interp_soa_context *bld,
for (unsigned chan = 0; chan < TGSI_NUM_CHANNELS; chan++) {
if (mask & (1 << chan)) {
LLVMValueRef index = lp_build_const_int32(gallivm, chan);
LLVMValueRef dadx = coeff_bld->zero;
LLVMValueRef dady = coeff_bld->zero;
LLVMValueRef a = coeff_bld->zero;
LLVMValueRef chan_pixoffx = pixoffx, chan_pixoffy = pixoffy;
@@ -346,7 +377,6 @@ attribs_update_simple(struct lp_build_interp_soa_context *bld,
case LP_INTERP_LINEAR:
if (attrib == 0 && chan == 0) {
dadx = coeff_bld->one;
if (sample_id) {
LLVMValueRef x_val_idx = LLVMBuildMul(gallivm->builder, sample_id, lp_build_const_int32(gallivm, 2), "");
x_val_idx = lp_build_array_get2(gallivm, bld->sample_pos_array_type,
@@ -355,9 +385,9 @@ attribs_update_simple(struct lp_build_interp_soa_context *bld,
} else {
a = lp_build_const_vec(gallivm, coeff_bld->type, bld->pos_offset);
}
a = lp_build_add(coeff_bld, chan_pixoffx, a);
}
else if (attrib == 0 && chan == 1) {
dady = coeff_bld->one;
if (sample_id) {
LLVMValueRef y_val_idx = LLVMBuildMul(gallivm->builder, sample_id, lp_build_const_int32(gallivm, 2), "");
y_val_idx = LLVMBuildAdd(gallivm->builder, y_val_idx, lp_build_const_int32(gallivm, 1), "");
@@ -367,18 +397,9 @@ attribs_update_simple(struct lp_build_interp_soa_context *bld,
} else {
a = lp_build_const_vec(gallivm, coeff_bld->type, bld->pos_offset);
}
a = lp_build_add(coeff_bld, chan_pixoffy, a);
}
else {
dadx = lp_build_extract_broadcast(gallivm, setup_bld->type,
coeff_bld->type, bld->dadxaos[attrib],
index);
dady = lp_build_extract_broadcast(gallivm, setup_bld->type,
coeff_bld->type, bld->dadyaos[attrib],
index);
a = lp_build_extract_broadcast(gallivm, setup_bld->type,
coeff_bld->type, bld->a0aos[attrib],
index);
if (bld->coverage_samples > 1) {
LLVMValueRef xoffset = pix_center_offset;
LLVMValueRef yoffset = pix_center_offset;
@@ -400,23 +421,32 @@ attribs_update_simple(struct lp_build_interp_soa_context *bld,
chan_pixoffx = lp_build_add(coeff_bld, chan_pixoffx, xoffset);
chan_pixoffy = lp_build_add(coeff_bld, chan_pixoffy, yoffset);
}
a = interp_attrib_linear(bld, attrib, index, chan_pixoffx, chan_pixoffy);
}
/*
* a = a0 + (x * dadx + y * dady)
*/
a = lp_build_fmuladd(builder, dadx, chan_pixoffx, a);
a = lp_build_fmuladd(builder, dady, chan_pixoffy, a);
if (interp == LP_INTERP_PERSPECTIVE) {
if (oow == NULL) {
LLVMValueRef w = bld->attribs[0][3];
LLVMValueRef w;
assert(attrib != 0);
assert(bld->mask[0] & TGSI_WRITEMASK_W);
if (bld->coverage_samples > 1 &&
(loc == TGSI_INTERPOLATE_LOC_SAMPLE ||
loc == TGSI_INTERPOLATE_LOC_CENTROID)) {
/*
* We can't use the precalculated 1/w since we didn't know
* the actual position yet (we were assuming center).
*/
LLVMValueRef indexw = lp_build_const_int32(gallivm, 3);
w = interp_attrib_linear(bld, 0, indexw, chan_pixoffx, chan_pixoffy);
}
else {
w = bld->attribs[0][3];
}
oow = lp_build_rcp(coeff_bld, w);
}
a = lp_build_mul(coeff_bld, a, oow);
}
break;
case LP_INTERP_CONSTANT:
@@ -456,6 +486,7 @@ static LLVMValueRef
lp_build_interp_soa_indirect(struct lp_build_interp_soa_context *bld,
struct gallivm_state *gallivm,
unsigned attrib, unsigned chan,
bool recalc_w,
LLVMValueRef indir_index,
LLVMValueRef pixoffx,
LLVMValueRef pixoffy)
@@ -516,11 +547,22 @@ lp_build_interp_soa_indirect(struct lp_build_interp_soa_context *bld,
a = lp_build_fmuladd(builder, dady, pixoffy, a);
if (interp == LP_INTERP_PERSPECTIVE) {
LLVMValueRef w = bld->attribs[0][3];
assert(attrib != 0);
assert(bld->mask[0] & TGSI_WRITEMASK_W);
LLVMValueRef oow = lp_build_rcp(coeff_bld, w);
a = lp_build_mul(coeff_bld, a, oow);
LLVMValueRef w;
assert(attrib != 0);
assert(bld->mask[0] & TGSI_WRITEMASK_W);
if (recalc_w) {
/*
* We can't use the precalculated 1/w since we didn't know
* the actual position yet (we were assuming center).
*/
LLVMValueRef indexw = lp_build_const_int32(gallivm, 3);
w = interp_attrib_linear(bld, 0, indexw, pixoffx, pixoffy);
}
else {
w = bld->attribs[0][3];
}
LLVMValueRef oow = lp_build_rcp(coeff_bld, w);
a = lp_build_mul(coeff_bld, a, oow);
}
break;
@@ -557,6 +599,7 @@ lp_build_interp_soa(struct lp_build_interp_soa_context *bld,
LLVMValueRef pixoffx;
LLVMValueRef pixoffy;
LLVMValueRef ptr;
bool recalc_w = false;
/* could do this with code-generated passed in pixel offsets too */
@@ -582,12 +625,16 @@ lp_build_interp_soa(struct lp_build_interp_soa_context *bld,
pixoffy = LLVMBuildFAdd(builder, pixoffy, pix_center_offset, "");
}
if (offsets[0])
if (offsets[0]) {
pixoffx = LLVMBuildFAdd(builder, pixoffx,
offsets[0], "");
if (offsets[1])
recalc_w = true;
}
if (offsets[1]) {
pixoffy = LLVMBuildFAdd(builder, pixoffy,
offsets[1], "");
recalc_w = true;
}
} else if (loc == TGSI_INTERPOLATE_LOC_SAMPLE) {
LLVMValueRef x_val_idx = LLVMBuildMul(gallivm->builder, offsets[0],
lp_build_const_int_vec(gallivm, bld->coeff_bld.type, 2 * 4), "");
@@ -616,6 +663,7 @@ lp_build_interp_soa(struct lp_build_interp_soa_context *bld,
if (bld->coverage_samples > 1) {
pixoffx = LLVMBuildFAdd(builder, pixoffx, xoffset, "");
pixoffy = LLVMBuildFAdd(builder, pixoffy, yoffset, "");
recalc_w = true;
}
} else if (loc == TGSI_INTERPOLATE_LOC_CENTROID) {
LLVMValueRef centroid_x_offset, centroid_y_offset;
@@ -629,6 +677,7 @@ lp_build_interp_soa(struct lp_build_interp_soa_context *bld,
pixoffx = LLVMBuildFAdd(builder, pixoffx, centroid_x_offset, "");
pixoffy = LLVMBuildFAdd(builder, pixoffy, centroid_y_offset, "");
recalc_w = true;
}
}
@@ -636,45 +685,37 @@ lp_build_interp_soa(struct lp_build_interp_soa_context *bld,
attrib++;
if (indir_index)
return lp_build_interp_soa_indirect(bld, gallivm, attrib, chan,
return lp_build_interp_soa_indirect(bld, gallivm, attrib, chan, recalc_w,
indir_index, pixoffx, pixoffy);
const enum lp_interp interp = bld->interp[attrib];
LLVMValueRef dadx = coeff_bld->zero;
LLVMValueRef dady = coeff_bld->zero;
LLVMValueRef a = coeff_bld->zero;
LLVMValueRef index = lp_build_const_int32(gallivm, chan);
switch (interp) {
case LP_INTERP_PERSPECTIVE:
FALLTHROUGH;
case LP_INTERP_LINEAR:
dadx = lp_build_extract_broadcast(gallivm, setup_bld->type,
coeff_bld->type, bld->dadxaos[attrib],
index);
dady = lp_build_extract_broadcast(gallivm, setup_bld->type,
coeff_bld->type, bld->dadyaos[attrib],
index);
a = lp_build_extract_broadcast(gallivm, setup_bld->type,
coeff_bld->type, bld->a0aos[attrib],
index);
/*
* a = a0 + (x * dadx + y * dady)
*/
a = lp_build_fmuladd(builder, dadx, pixoffx, a);
a = lp_build_fmuladd(builder, dady, pixoffy, a);
a = interp_attrib_linear(bld, attrib, index, pixoffx, pixoffy);
if (interp == LP_INTERP_PERSPECTIVE) {
LLVMValueRef w = bld->attribs[0][3];
assert(attrib != 0);
assert(bld->mask[0] & TGSI_WRITEMASK_W);
LLVMValueRef oow = lp_build_rcp(coeff_bld, w);
a = lp_build_mul(coeff_bld, a, oow);
LLVMValueRef w;
assert(attrib != 0);
assert(bld->mask[0] & TGSI_WRITEMASK_W);
if (recalc_w) {
/*
* We can't use the precalculated 1/w since we didn't know
* the actual position yet (we were assuming center).
*/
LLVMValueRef indexw = lp_build_const_int32(gallivm, 3);
w = interp_attrib_linear(bld, 0, indexw, pixoffx, pixoffy);
}
else {
w = bld->attribs[0][3];
}
LLVMValueRef oow = lp_build_rcp(coeff_bld, w);
a = lp_build_mul(coeff_bld, a, oow);
}
break;