ac/llvm: add AC_FLOAT_MODE_ROUND_TO_ZERO

Because some instructions will be optimized by the backend compiler,
the driver has to manually flush to zero to keep the result exact.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

src/amd/llvm/ac_llvm_build.c

@@ -73,6 +73,7 @@ ac_llvm_context_init(struct ac_llvm_context *ctx,
 	ctx->family = family;
 	ctx->wave_size = wave_size;
 	ctx->ballot_mask_bits = ballot_mask_bits;
+	ctx->float_mode = float_mode;
 	ctx->module = ac_create_module(wave_size == 32 ? compiler->tm_wave32
 						       : compiler->tm,
 				       ctx->context);

src/amd/llvm/ac_llvm_build.h

@@ -120,6 +120,8 @@ struct ac_llvm_context {
 	unsigned wave_size;
 	unsigned ballot_mask_bits;
 
+	unsigned float_mode;
+
 	LLVMValueRef lds;
 };
 

src/amd/llvm/ac_llvm_helper.cpp

@@ -82,6 +82,7 @@ LLVMBuilderRef ac_create_builder(LLVMContextRef ctx,
 
 	switch (float_mode) {
 	case AC_FLOAT_MODE_DEFAULT:
+	case AC_FLOAT_MODE_DENORM_FLUSH_TO_ZERO:
 		break;
 	case AC_FLOAT_MODE_NO_SIGNED_ZEROS_FP_MATH:
 		flags.setNoSignedZeros();

src/amd/llvm/ac_llvm_util.h

@@ -73,6 +73,7 @@ enum ac_float_mode {
 	AC_FLOAT_MODE_DEFAULT,
 	AC_FLOAT_MODE_NO_SIGNED_ZEROS_FP_MATH,
 	AC_FLOAT_MODE_UNSAFE_FP_MATH,
+	AC_FLOAT_MODE_DENORM_FLUSH_TO_ZERO,
 };
 
 /* Per-thread persistent LLVM objects. */