From: Dave Airlie <airl...@redhat.com>
This is ported from radeonsi, and I can see at least one
Talos shader drops an export due to this, and saves some
VGPR usage.
Signed-off-by: Dave Airlie <airl...@redhat.com>
---
src/amd/common/ac_nir_to_llvm.c | 178 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 178 insertions(+)
diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index ab929bc..38d5359 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -5753,6 +5753,182 @@ static void ac_llvm_finalize_module(struct
nir_to_llvm_context * ctx)
LLVMDisposePassManager(passmgr);
}
+#define EXP_TARGET (HAVE_LLVM >= 0x0500 ? 0 : 3)
+#define EXP_OUT0 (HAVE_LLVM >= 0x0500 ? 2 : 5)
+
+/* Return true if the PARAM export has been eliminated. */
+static bool
+ac_eliminate_const_output(struct nir_to_llvm_context *ctx,
+ struct ac_vs_output_info *outinfo,
+ LLVMValueRef inst, unsigned offset)
+{
+ unsigned i, default_val; /* SPI_PS_INPUT_CNTL_i.DEFAULT_VAL */
+ bool is_zero[4] = {}, is_one[4] = {};
+
+ for (i = 0; i < 4; i++) {
+ LLVMBool loses_info;
+ LLVMValueRef p = LLVMGetOperand(inst, EXP_OUT0 + i);
+
+ /* It's a constant expression. Undef outputs are eliminated
too. */
+ if (LLVMIsUndef(p)) {
+ is_zero[i] = true;
+ is_one[i] = true;
+ } else if (LLVMIsAConstantFP(p)) {
+ double a = LLVMConstRealGetDouble(p, &loses_info);
+
+ if (a == 0)
+ is_zero[i] = true;
+ else if (a == 1)
+ is_one[i] = true;
+ else
+
+ return false; /* other constant */
+ } else
+ return false;
+ }
+
+ /* Only certain combinations of 0 and 1 can be eliminated. */
+ if (is_zero[0] && is_zero[1] && is_zero[2])
+ default_val = is_zero[3] ? 0 : 1;
+ else if (is_one[0] && is_one[1] && is_one[2])
+ default_val = is_zero[3] ? 2 : 3;
+ else
+ return false;
+
+ /* The PARAM export can be represented as DEFAULT_VAL. Kill it. */
+ LLVMInstructionEraseFromParent(inst);
+
+ /* Change OFFSET to DEFAULT_VAL. */
+ for (i = 0; i < VARYING_SLOT_MAX; i++) {
+ if (outinfo->vs_output_param_offset[i] == offset) {
+ outinfo->vs_output_param_offset[i] =
+ EXP_PARAM_DEFAULT_VAL_0000 + default_val;
+ break;
+ }
+ }
+ return true;
+}
+
+struct si_vs_exports {
+ unsigned num;
+ unsigned offset[VARYING_SLOT_MAX];
+ LLVMValueRef inst[VARYING_SLOT_MAX];
+};
+
+static bool
+ac_is_function(LLVMValueRef v)
+{
+ return LLVMGetValueKind(v) == LLVMFunctionValueKind;
+}
+
+static void
+ac_eliminate_const_vs_outputs(struct nir_to_llvm_context *ctx)
+{
+ LLVMBasicBlockRef bb;
+ struct si_vs_exports exports;
+ bool removed_any = false;
+ struct ac_vs_output_info *outinfo;
+ exports.num = 0;
+
+ if (ctx->stage == MESA_SHADER_FRAGMENT ||
+ ctx->stage == MESA_SHADER_COMPUTE ||
+ ctx->stage == MESA_SHADER_TESS_CTRL ||
+ ctx->stage == MESA_SHADER_GEOMETRY)
+ return;
+
+ if (ctx->stage == MESA_SHADER_VERTEX) {
+ if (ctx->options->key.vs.as_ls ||
+ ctx->options->key.vs.as_es)
+ return;
+ outinfo = &ctx->shader_info->vs.outinfo;
+ }
+
+ if (ctx->stage == MESA_SHADER_TESS_EVAL) {
+ if (ctx->options->key.vs.as_es)
+ return;
+ outinfo = &ctx->shader_info->tes.outinfo;
+ }
+
+ /* Process all LLVM instructions. */
+ bb = LLVMGetFirstBasicBlock(ctx->main_function);
+ while (bb) {
+ LLVMValueRef inst = LLVMGetFirstInstruction(bb);
+
+ while (inst) {
+ LLVMValueRef cur = inst;
+ inst = LLVMGetNextInstruction(inst);
+
+ if (LLVMGetInstructionOpcode(cur) != LLVMCall)
+ continue;
+
+ LLVMValueRef callee = LLVMGetCalledValue(cur);
+
+ if (!ac_is_function(callee))
+ continue;
+
+ const char *name = LLVMGetValueName(callee);
+ unsigned num_args = LLVMCountParams(callee);
+
+ /* Check if this is an export instruction. */
+ if ((num_args != 9 && num_args != 8) ||
+ (strcmp(name, "llvm.SI.export") &&
+ strcmp(name, "llvm.amdgcn.exp.f32")))
+ continue;
+
+ LLVMValueRef arg = LLVMGetOperand(cur, EXP_TARGET);
+ unsigned target = LLVMConstIntGetZExtValue(arg);
+
+ if (target < V_008DFC_SQ_EXP_PARAM)
+ continue;
+
+ target -= V_008DFC_SQ_EXP_PARAM;
+
+ /* Eliminate constant value PARAM exports. */
+ if (ac_eliminate_const_output(ctx, outinfo, cur,
target)) {
+ removed_any = true;
+ } else {
+ exports.offset[exports.num] = target;
+ exports.inst[exports.num] = cur;
+ exports.num++;
+ }
+ }
+ bb = LLVMGetNextBasicBlock(bb);
+ }
+
+ /* Remove holes in export memory due to removed PARAM exports.
+ * This is done by renumbering all PARAM exports.
+ */
+ if (removed_any) {
+ ubyte current_offset[VARYING_SLOT_MAX];
+ unsigned new_count = 0;
+ unsigned out, i;
+
+ /* Make a copy of the offsets. We need the old version while
+ * we are modifying some of them. */
+ assert(sizeof(current_offset) ==
+ sizeof(outinfo->vs_output_param_offset));
+ memcpy(current_offset, outinfo->vs_output_param_offset,
+ sizeof(current_offset));
+
+ for (i = 0; i < exports.num; i++) {
+ unsigned offset = exports.offset[i];
+
+ for (out = 0; out < VARYING_SLOT_MAX; out++) {
+ if (current_offset[out] != offset)
+ continue;
+
+ LLVMSetOperand(exports.inst[i], EXP_TARGET,
+ LLVMConstInt(ctx->i32,
+
V_008DFC_SQ_EXP_PARAM + new_count, 0));
+ outinfo->vs_output_param_offset[out] =
new_count;
+ new_count++;
+ break;
+ }
+ }
+ outinfo->param_exports = new_count;
+ }
+}
+
static void
ac_setup_rings(struct nir_to_llvm_context *ctx)
{
@@ -5890,6 +6066,8 @@ LLVMModuleRef
ac_translate_nir_to_llvm(LLVMTargetMachineRef tm,
LLVMBuildRetVoid(ctx.builder);
ac_llvm_finalize_module(&ctx);
+
+ ac_eliminate_const_vs_outputs(&ctx);
free(ctx.locals);
ralloc_free(ctx.defs);
ralloc_free(ctx.phis);
--
2.7.4
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