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gallivm: fix SCALED -> NORM conversions 

Such conversions (which are most likely rather pointless in practice) were
resulting in shifts with negative shift counts and shifts with counts the same
as the bit width. This was always undefined in llvm, the code generated was
rather horrendous but happened to work.
So make sure such shifts are filtered out and replaced with something that
works (the generated code is still just as horrendous as before).

This fixes lp_test_format, https://bugs.freedesktop.org/show_bug.cgi?id=73846.

v2: prettify by using build context shift helpers.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
This commit is contained in:
Roland Scheidegger 2014-06-18 01:34:49 +02:00
parent 7928b946ad
commit 56335b4441
1 changed files with 23 additions and 16 deletions
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39
src/gallium/auxiliary/gallivm/lp_bld_conv.c
View File

@ -792,29 +792,23 @@ lp_build_conv(struct gallivm_state *gallivm,
unsigned dst_shift = lp_const_shift(dst_type);
unsigned src_offset = lp_const_offset(src_type);
unsigned dst_offset = lp_const_offset(dst_type);
struct lp_build_context bld;
lp_build_context_init(&bld, gallivm, tmp_type);
/* Compensate for different offsets */
if (dst_offset > src_offset && src_type.width > dst_type.width) {
/* sscaled -> unorm and similar would cause negative shift count, skip */
if (dst_offset > src_offset && src_type.width > dst_type.width && src_shift > 0) {
for (i = 0; i < num_tmps; ++i) {
LLVMValueRef shifted;
LLVMValueRef shift = lp_build_const_int_vec(gallivm, tmp_type, src_shift - 1);
if(src_type.sign)
shifted = LLVMBuildAShr(builder, tmp[i], shift, "");
else
shifted = LLVMBuildLShr(builder, tmp[i], shift, "");
shifted = lp_build_shr_imm(&bld, tmp[i], src_shift - 1);
tmp[i] = LLVMBuildSub(builder, tmp[i], shifted, "");
}
}
if(src_shift > dst_shift) {
LLVMValueRef shift = lp_build_const_int_vec(gallivm, tmp_type,
src_shift - dst_shift);
for(i = 0; i < num_tmps; ++i)
if(src_type.sign)
tmp[i] = LLVMBuildAShr(builder, tmp[i], shift, "");
else
tmp[i] = LLVMBuildLShr(builder, tmp[i], shift, "");
tmp[i] = lp_build_shr_imm(&bld, tmp[i], src_shift - dst_shift);
}
}
@ -900,14 +894,27 @@ lp_build_conv(struct gallivm_state *gallivm,
unsigned dst_shift = lp_const_shift(dst_type);
unsigned src_offset = lp_const_offset(src_type);
unsigned dst_offset = lp_const_offset(dst_type);
struct lp_build_context bld;
lp_build_context_init(&bld, gallivm, tmp_type);
if (src_shift < dst_shift) {
LLVMValueRef pre_shift[LP_MAX_VECTOR_LENGTH];
LLVMValueRef shift = lp_build_const_int_vec(gallivm, tmp_type, dst_shift - src_shift);
for (i = 0; i < num_tmps; ++i) {
pre_shift[i] = tmp[i];
tmp[i] = LLVMBuildShl(builder, tmp[i], shift, "");
if (dst_shift - src_shift < dst_type.width) {
for (i = 0; i < num_tmps; ++i) {
pre_shift[i] = tmp[i];
tmp[i] = lp_build_shl_imm(&bld, tmp[i], dst_shift - src_shift);
}
}
else {
/*
* This happens for things like sscaled -> unorm conversions. Shift
* counts equal to bit width cause undefined results, so hack around it.
*/
for (i = 0; i < num_tmps; ++i) {
pre_shift[i] = tmp[i];
tmp[i] = lp_build_zero(gallivm, dst_type);
}
}
/* Compensate for different offsets */