Module: Mesa
Branch: master
Commit: 2c2aaf275c1edba38c552ac74de4d46bb2ebfbe8
URL:
http://cgit.freedesktop.org/mesa/mesa/commit/?id=2c2aaf275c1edba38c552ac74de4d46bb2ebfbe8
Author: Samuel Pitoiset <samuel.pitoi...@gmail.com>
Date: Mon Oct 14 15:39:06 2019 +0200
ac/llvm: force fneg/fabs to flush denorms to zero if requested
LLVM optimizes these instructions with XOR/AND and it loses
the sign bit.
Signed-off-by: Samuel Pitoiset <samuel.pitoi...@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <b...@basnieuwenhuizen.nl>
---
src/amd/llvm/ac_nir_to_llvm.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/src/amd/llvm/ac_nir_to_llvm.c b/src/amd/llvm/ac_nir_to_llvm.c
index ab042d36083..cd7091ad163 100644
--- a/src/amd/llvm/ac_nir_to_llvm.c
+++ b/src/amd/llvm/ac_nir_to_llvm.c
@@ -516,6 +516,13 @@ static void visit_alu(struct ac_nir_context *ctx, const
nir_alu_instr *instr)
case nir_op_fneg:
src[0] = ac_to_float(&ctx->ac, src[0]);
result = LLVMBuildFNeg(ctx->ac.builder, src[0], "");
+ if (ctx->ac.float_mode == AC_FLOAT_MODE_DENORM_FLUSH_TO_ZERO) {
+ /* fneg will be optimized by backend compiler with sign
+ * bit removed via XOR. This is probably a LLVM bug.
+ */
+ result = ac_build_canonicalize(&ctx->ac, result,
+
instr->dest.dest.ssa.bit_size);
+ }
break;
case nir_op_ineg:
result = LLVMBuildNeg(ctx->ac.builder, src[0], "");
@@ -646,6 +653,13 @@ static void visit_alu(struct ac_nir_context *ctx, const
nir_alu_instr *instr)
case nir_op_fabs:
result = emit_intrin_1f_param(&ctx->ac, "llvm.fabs",
ac_to_float_type(&ctx->ac,
def_type), src[0]);
+ if (ctx->ac.float_mode == AC_FLOAT_MODE_DENORM_FLUSH_TO_ZERO) {
+ /* fabs will be optimized by backend compiler with sign
+ * bit removed via AND.
+ */
+ result = ac_build_canonicalize(&ctx->ac, result,
+
instr->dest.dest.ssa.bit_size);
+ }
break;
case nir_op_iabs:
result = emit_iabs(&ctx->ac, src[0]);
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