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mesa: fix emit_clamp() so that we don't use an output register as temporary

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IR_CLAMP is decomposed into OPCODE_MIN+OPCODE_MAX.  Allocate a temporary
register for the intermediate value so we don't inadvertantly use an output
register (which are write-only on some GPUs).
This commit is contained in:
Brian Paul 2008-03-14 13:50:01 -06:00
parent 14150bc856
commit 7dc449d406
1 changed files with 12 additions and 3 deletions
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15
src/mesa/shader/slang/slang_emit.c
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@ -677,6 +677,7 @@ static struct prog_instruction *
emit_clamp(slang_emit_info *emitInfo, slang_ir_node *n)
{
struct prog_instruction *inst;
slang_ir_node tmpNode;
assert(n->Opcode == IR_CLAMP);
/* ch[0] = value
@ -722,18 +723,26 @@ emit_clamp(slang_emit_info *emitInfo, slang_ir_node *n)
emit(emitInfo, n->Children[1]);
emit(emitInfo, n->Children[2]);
/* Some GPUs don't allow reading from output registers. So if the
* dest for this clamp() is an output reg, we can't use that reg for
* the intermediate result. Use a temp register instead.
*/
alloc_temp_storage(emitInfo, &tmpNode, n->Store->Size);
/* tmp = max(ch[0], ch[1]) */
inst = new_instruction(emitInfo, OPCODE_MAX);
storage_to_dst_reg(&inst->DstReg, n->Store, n->Writemask);
storage_to_dst_reg(&inst->DstReg, tmpNode.Store, n->Writemask);
storage_to_src_reg(&inst->SrcReg[0], n->Children[0]->Store);
storage_to_src_reg(&inst->SrcReg[1], n->Children[1]->Store);
/* tmp = min(tmp, ch[2]) */
/* n->dest = min(tmp, ch[2]) */
inst = new_instruction(emitInfo, OPCODE_MIN);
storage_to_dst_reg(&inst->DstReg, n->Store, n->Writemask);
storage_to_src_reg(&inst->SrcReg[0], n->Store);
storage_to_src_reg(&inst->SrcReg[0], tmpNode.Store);
storage_to_src_reg(&inst->SrcReg[1], n->Children[2]->Store);
free_temp_storage(emitInfo->vt, &tmpNode);
return inst;
}