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-rw-r--r--src/gallium/auxiliary/gallivm/lp_bld_sample.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_sample.c b/src/gallium/auxiliary/gallivm/lp_bld_sample.c
index 19e380a8dce..44f44ff1aa4 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_sample.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_sample.c
@@ -655,11 +655,21 @@ lp_build_sample_partial_offset(struct lp_build_context *bld,
* Pixel blocks have power of two dimensions. LLVM should convert the
* rem/div to bit arithmetic.
* TODO: Verify this.
+ * It does indeed BUT it does transform it to scalar (and back) when doing so
+ * (using roughly extract, shift/and, mov, unpack) (llvm 2.7).
+ * The generated code looks seriously unfunny and is quite expensive.
*/
-
+#if 0
LLVMValueRef block_width = lp_build_const_int_vec(bld->type, block_length);
subcoord = LLVMBuildURem(bld->builder, coord, block_width, "");
coord = LLVMBuildUDiv(bld->builder, coord, block_width, "");
+#else
+ unsigned logbase2 = util_unsigned_logbase2(block_length);
+ LLVMValueRef block_shift = lp_build_const_int_vec(bld->type, logbase2);
+ LLVMValueRef block_mask = lp_build_const_int_vec(bld->type, block_length - 1);
+ subcoord = LLVMBuildAnd(bld->builder, coord, block_mask, "");
+ coord = LLVMBuildLShr(bld->builder, coord, block_shift, "");
+#endif
}
offset = lp_build_mul(bld, coord, stride);