Module: Mesa
Branch: glsl-to-tgsi
Commit: 95b86e40fbac83918139d1cdcadb8f6471233d82
URL:
http://cgit.freedesktop.org/mesa/mesa/commit/?id=95b86e40fbac83918139d1cdcadb8f6471233d82
Author: Bryan Cain <bryanca...@gmail.com>
Date: Thu Jun 16 18:36:16 2011 -0500
st/mesa: implement simplify_cmp pass needed by r300g
---
src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 95 ++++++++++++++++++++++++++++
1 files changed, 95 insertions(+), 0 deletions(-)
diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index 6c92441..322bfbb 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -374,6 +374,7 @@ public:
bool process_move_condition(ir_rvalue *ir);
void remove_output_reads(gl_register_file type);
+ void simplify_cmp(void);
void rename_temp_register(int index, int new_index);
int get_first_temp_read(int index);
@@ -2788,6 +2789,97 @@
glsl_to_tgsi_visitor::remove_output_reads(gl_register_file type)
}
}
+/**
+ * Returns the mask of channels (bitmask of WRITEMASK_X,Y,Z,W) which
+ * are read from the given src in this instruction
+ */
+static int
+get_src_arg_mask(st_dst_reg dst, st_src_reg src)
+{
+ int read_mask = 0, comp;
+
+ /* Now, given the src swizzle and the written channels, find which
+ * components are actually read
+ */
+ for (comp = 0; comp < 4; ++comp) {
+ const unsigned coord = GET_SWZ(src.swizzle, comp);
+ ASSERT(coord < 4);
+ if (dst.writemask & (1 << comp) && coord <= SWIZZLE_W)
+ read_mask |= 1 << coord;
+ }
+
+ return read_mask;
+}
+
+/**
+ * This pass replaces CMP T0, T1 T2 T0 with MOV T0, T2 when the CMP
+ * instruction is the first instruction to write to register T0. There are
+ * several lowering passes done in GLSL IR (e.g. branches and
+ * relative addressing) that create a large number of conditional assignments
+ * that ir_to_mesa converts to CMP instructions like the one mentioned above.
+ *
+ * Here is why this conversion is safe:
+ * CMP T0, T1 T2 T0 can be expanded to:
+ * if (T1 < 0.0)
+ * MOV T0, T2;
+ * else
+ * MOV T0, T0;
+ *
+ * If (T1 < 0.0) evaluates to true then our replacement MOV T0, T2 is the same
+ * as the original program. If (T1 < 0.0) evaluates to false, executing
+ * MOV T0, T0 will store a garbage value in T0 since T0 is uninitialized.
+ * Therefore, it doesn't matter that we are replacing MOV T0, T0 with MOV T0,
T2
+ * because any instruction that was going to read from T0 after this was going
+ * to read a garbage value anyway.
+ */
+void
+glsl_to_tgsi_visitor::simplify_cmp(void)
+{
+ unsigned tempWrites[MAX_PROGRAM_TEMPS];
+ unsigned outputWrites[MAX_PROGRAM_OUTPUTS];
+
+ memset(tempWrites, 0, sizeof(tempWrites));
+ memset(outputWrites, 0, sizeof(outputWrites));
+
+ foreach_iter(exec_list_iterator, iter, this->instructions) {
+ glsl_to_tgsi_instruction *inst = (glsl_to_tgsi_instruction *)iter.get();
+ unsigned prevWriteMask = 0;
+
+ /* Give up if we encounter relative addressing or flow control. */
+ if (inst->dst.reladdr ||
+ tgsi_get_opcode_info(inst->op)->is_branch ||
+ inst->op == TGSI_OPCODE_BGNSUB ||
+ inst->op == TGSI_OPCODE_CONT ||
+ inst->op == TGSI_OPCODE_END ||
+ inst->op == TGSI_OPCODE_ENDSUB ||
+ inst->op == TGSI_OPCODE_RET) {
+ return;
+ }
+
+ if (inst->dst.file == PROGRAM_OUTPUT) {
+ assert(inst->dst.index < MAX_PROGRAM_OUTPUTS);
+ prevWriteMask = outputWrites[inst->dst.index];
+ outputWrites[inst->dst.index] |= inst->dst.writemask;
+ } else if (inst->dst.file == PROGRAM_TEMPORARY) {
+ assert(inst->dst.index < MAX_PROGRAM_TEMPS);
+ prevWriteMask = tempWrites[inst->dst.index];
+ tempWrites[inst->dst.index] |= inst->dst.writemask;
+ }
+
+ /* For a CMP to be considered a conditional write, the destination
+ * register and source register two must be the same. */
+ if (inst->op == TGSI_OPCODE_CMP
+ && !(inst->dst.writemask & prevWriteMask)
+ && inst->src[2].file == inst->dst.file
+ && inst->src[2].index == inst->dst.index
+ && inst->dst.writemask == get_src_arg_mask(inst->dst, inst->src[2]))
{
+
+ inst->op = TGSI_OPCODE_MOV;
+ inst->src[0] = inst->src[1];
+ }
+ }
+}
+
/* Replaces all references to a temporary register index with another index. */
void
glsl_to_tgsi_visitor::rename_temp_register(int index, int new_index)
@@ -4170,6 +4262,9 @@ get_mesa_program(struct gl_context *ctx,
v->remove_output_reads(PROGRAM_OUTPUT);
if (target == GL_VERTEX_PROGRAM_ARB)
v->remove_output_reads(PROGRAM_VARYING);
+
+ /* Perform the simplify_cmp optimization, which is required by r300g. */
+ v->simplify_cmp();
/* Perform optimizations on the instructions in the glsl_to_tgsi_visitor.
* FIXME: These passes to optimize temporary registers don't work when there
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