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ac: revert new LLVM 7.0 behavior for fdiv

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Cc: 18.2 <mesa-stable@lists.freedesktop.org>
Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>
This commit is contained in:
Marek Olšák 2018-08-24 23:00:37 -04:00
parent 662db03577
commit a5f35aa742
1 changed files with 8 additions and 1 deletions
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9
src/amd/common/ac_llvm_build.c
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@ -561,7 +561,14 @@ ac_build_fdiv(struct ac_llvm_context *ctx,
LLVMValueRef num,
LLVMValueRef den)
{
LLVMValueRef ret = LLVMBuildFDiv(ctx->builder, num, den, "");
/* If we do (num / den), LLVM >= 7.0 does:
* return num * v_rcp_f32(den * (fabs(den) > 0x1.0p+96f ? 0x1.0p-32f : 1.0f));
*
* If we do (num * (1 / den)), LLVM does:
* return num * v_rcp_f32(den);
*/
LLVMValueRef rcp = LLVMBuildFDiv(ctx->builder, ctx->f32_1, den, "");
LLVMValueRef ret = LLVMBuildFMul(ctx->builder, num, rcp, "");
/* Use v_rcp_f32 instead of precise division. */
if (!LLVMIsConstant(ret))