[Mesa-dev] [PATCH] gallivm: fix [IU]MUL_HI regression harder

[Nicolai Hähnle]

On 09.11.2016 14:46, Roland Scheidegger wrote:
> Reviewed-by: Roland Scheidegger <sroland at vmware.com>
>
> I'm curious though, is for radeonsi zext not equivalent to interleaving
> the low 32bits of each number with zeros (and hence doing the a
> uninterleave doesn't give you back the low respectively high bits)?

radeonsi ends up calling lp_build_mul_32_lohi once for each component of 
the vector, with no vector types involved at all, it's all plain i32 and 
i64. This is better for the CodeGen backend in LLVM.

The code was previously returning a <1 x i32> for each component, and 
that caused the later stages of opcode handling to get confused about 
what to do with the result.

Cheers,
Nicolai

>
> Roland
>
> Am 09.11.2016 um 12:46 schrieb Nicolai Hähnle:
>> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>>
>> The fix in commit 88f791db75e9f065bac8134e0937e1b76600aa36 was insufficient
>> for radeonsi because the vector case was not handled properly. It seems
>> piglit only covers the scalar case, unfortunately.
>>
>> Fixes GL45-CTS.shader_bitfield_operation.[iu]mulExtended.*
>> ---
>>  src/gallium/auxiliary/gallivm/lp_bld_arit.c | 20 ++++++++++++--------
>>  1 file changed, 12 insertions(+), 8 deletions(-)
>>
>> diff --git a/src/gallium/auxiliary/gallivm/lp_bld_arit.c b/src/gallium/auxiliary/gallivm/lp_bld_arit.c
>> index 43ad238..5553cb1 100644
>> --- a/src/gallium/auxiliary/gallivm/lp_bld_arit.c
>> +++ b/src/gallium/auxiliary/gallivm/lp_bld_arit.c
>> @@ -1230,42 +1230,46 @@ lp_build_mul_32_lohi_cpu(struct lp_build_context *bld,
>>   * Emits generic code.
>>   */
>>  LLVMValueRef
>>  lp_build_mul_32_lohi(struct lp_build_context *bld,
>>                       LLVMValueRef a,
>>                       LLVMValueRef b,
>>                       LLVMValueRef *res_hi)
>>  {
>>     struct gallivm_state *gallivm = bld->gallivm;
>>     LLVMBuilderRef builder = gallivm->builder;
>> -   LLVMValueRef tmp;
>> +   LLVMValueRef tmp, shift, res_lo;
>>     struct lp_type type_tmp;
>> -   LLVMTypeRef wide_type, cast_type;
>> +   LLVMTypeRef wide_type, narrow_type;
>>
>>     type_tmp = bld->type;
>> +   narrow_type = lp_build_vec_type(gallivm, type_tmp);
>>     type_tmp.width *= 2;
>>     wide_type = lp_build_vec_type(gallivm, type_tmp);
>> -   type_tmp = bld->type;
>> -   type_tmp.length *= 2;
>> -   cast_type = lp_build_vec_type(gallivm, type_tmp);
>> +   shift = lp_build_const_vec(gallivm, type_tmp, 32);
>>
>>     if (bld->type.sign) {
>>        a = LLVMBuildSExt(builder, a, wide_type, "");
>>        b = LLVMBuildSExt(builder, b, wide_type, "");
>>     } else {
>>        a = LLVMBuildZExt(builder, a, wide_type, "");
>>        b = LLVMBuildZExt(builder, b, wide_type, "");
>>     }
>>     tmp = LLVMBuildMul(builder, a, b, "");
>> -   tmp = LLVMBuildBitCast(builder, tmp, cast_type, "");
>> -   *res_hi = lp_build_uninterleave1(gallivm, bld->type.length * 2, tmp, 1);
>> -   return lp_build_uninterleave1(gallivm, bld->type.length * 2, tmp, 0);
>> +
>> +   res_lo = LLVMBuildTrunc(builder, tmp, narrow_type, "");
>> +
>> +   /* Since we truncate anyway, LShr and AShr are equivalent. */
>> +   tmp = LLVMBuildLShr(builder, tmp, shift, "");
>> +   *res_hi = LLVMBuildTrunc(builder, tmp, narrow_type, "");
>> +
>> +   return res_lo;
>>  }
>>
>>
>>  /* a * b + c */
>>  LLVMValueRef
>>  lp_build_mad(struct lp_build_context *bld,
>>               LLVMValueRef a,
>>               LLVMValueRef b,
>>               LLVMValueRef c)
>>  {
>>
>