r300g: implement TRUNC correctly

This fixes some integer division tests.

1 files changed, 31 insertions, 0 deletions

diff --git a/src/gallium/drivers/r300/compiler/radeon_program_alu.c b/src/gallium/drivers/r300/compiler/radeon_program_alu.c
index b3da311498b..f4ee86de5d0 100644
--- a/src/gallium/drivers/r300/compiler/radeon_program_alu.c
+++ b/src/gallium/drivers/r300/compiler/radeon_program_alu.c
@@ -321,6 +321,24 @@ static void transform_FLR(struct radeon_compiler* c,
 	rc_remove_instruction(inst);
 }
 
+static void transform_TRUNC(struct radeon_compiler* c,
+	struct rc_instruction* inst)
+{
+	/* Definition of trunc:
+	 *   trunc(x) = (abs(x) - fract(abs(x))) * sgn(x)
+	 *
+	 * The multiplication by sgn(x) can be simplified using CMP:
+	 *   y * sgn(x) = (x < 0 ? -y : y)
+	 */
+	struct rc_dst_register dst = try_to_reuse_dst(c, inst);
+	emit1(c, inst->Prev, RC_OPCODE_FRC, 0, dst, absolute(inst->U.I.SrcReg[0]));
+	emit2(c, inst->Prev, RC_OPCODE_ADD, 0, dst, absolute(inst->U.I.SrcReg[0]),
+	      negate(srcreg(RC_FILE_TEMPORARY, dst.Index)));
+	emit3(c, inst->Prev, RC_OPCODE_CMP, &inst->U.I, inst->U.I.DstReg, inst->U.I.SrcReg[0],
+	      negate(srcreg(RC_FILE_TEMPORARY, dst.Index)), srcreg(RC_FILE_TEMPORARY, dst.Index));
+	rc_remove_instruction(inst);
+}
+
 /**
  * Definition of LIT (from ARB_fragment_program):
  *
@@ -666,6 +684,7 @@ int radeonTransformALU(
 	case RC_OPCODE_SSG: transform_SSG(c, inst); return 1;
 	case RC_OPCODE_SUB: transform_SUB(c, inst); return 1;
 	case RC_OPCODE_SWZ: transform_SWZ(c, inst); return 1;
+	case RC_OPCODE_TRUNC: transform_TRUNC(c, inst); return 1;
 	case RC_OPCODE_XPD: transform_XPD(c, inst); return 1;
 	default:
 		return 0;
@@ -866,6 +885,17 @@ static void transform_r300_vertex_SSG(struct radeon_compiler* c,
 	rc_remove_instruction(inst);
 }
 
+static void transform_vertex_TRUNC(struct radeon_compiler* c,
+	struct rc_instruction* inst)
+{
+	struct rc_instruction *next = inst->Next;
+
+	/* next->Prev is removed after each transformation and replaced
+	 * by a new instruction. */
+	transform_TRUNC(c, next->Prev);
+	transform_r300_vertex_CMP(c, next->Prev);
+}
+
 /**
  * For use with rc_local_transform, this transforms non-native ALU
  * instructions of the r300 up to r500 vertex engine.
@@ -904,6 +934,7 @@ int r300_transform_vertex_alu(
 	case RC_OPCODE_SSG: transform_r300_vertex_SSG(c, inst); return 1;
 	case RC_OPCODE_SUB: transform_SUB(c, inst); return 1;
 	case RC_OPCODE_SWZ: transform_SWZ(c, inst); return 1;
+	case RC_OPCODE_TRUNC: transform_vertex_TRUNC(c, inst); return 1;
 	case RC_OPCODE_XPD: transform_XPD(c, inst); return 1;
 	default:
 		return 0;