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authorJosé Fonseca <jfonseca@vmware.com>2009-10-25 09:16:38 +0000
committerJosé Fonseca <jfonseca@vmware.com>2009-10-25 09:53:49 +0000
commitf3893ca9c8bfdba9323ef2fc179ac203e85eda70 (patch)
tree7eed647cbc37c6945ed29bbd1ca3caf58f9b2d4e /src/gallium/drivers
parentbfd7a9ca967e5521fb3847db8615127c3ee7b9b3 (diff)
llvmpipe: Make lerping work for 8.8 fixed point values.
Diffstat (limited to 'src/gallium/drivers')
-rw-r--r--src/gallium/drivers/llvmpipe/lp_bld_arit.c54
1 files changed, 50 insertions, 4 deletions
diff --git a/src/gallium/drivers/llvmpipe/lp_bld_arit.c b/src/gallium/drivers/llvmpipe/lp_bld_arit.c
index 83ca06acf8..93e797cb44 100644
--- a/src/gallium/drivers/llvmpipe/lp_bld_arit.c
+++ b/src/gallium/drivers/llvmpipe/lp_bld_arit.c
@@ -361,6 +361,8 @@ lp_build_mul(struct lp_build_context *bld,
LLVMValueRef b)
{
const struct lp_type type = bld->type;
+ LLVMValueRef shift;
+ LLVMValueRef res;
if(a == bld->zero)
return bld->zero;
@@ -394,10 +396,31 @@ lp_build_mul(struct lp_build_context *bld,
assert(0);
}
- if(LLVMIsConstant(a) && LLVMIsConstant(b))
- return LLVMConstMul(a, b);
+ if(type.fixed)
+ shift = lp_build_int_const_scalar(type, type.width/2);
+ else
+ shift = NULL;
+
+ if(LLVMIsConstant(a) && LLVMIsConstant(b)) {
+ res = LLVMConstMul(a, b);
+ if(shift) {
+ if(type.sign)
+ res = LLVMConstAShr(res, shift);
+ else
+ res = LLVMConstLShr(res, shift);
+ }
+ }
+ else {
+ res = LLVMBuildMul(bld->builder, a, b, "");
+ if(shift) {
+ if(type.sign)
+ res = LLVMBuildAShr(bld->builder, res, shift, "");
+ else
+ res = LLVMBuildLShr(bld->builder, res, shift, "");
+ }
+ }
- return LLVMBuildMul(bld->builder, a, b, "");
+ return res;
}
@@ -432,13 +455,36 @@ lp_build_div(struct lp_build_context *bld,
}
+/**
+ * Linear interpolation.
+ *
+ * This also works for integer values with a few caveats.
+ *
+ * @sa http://www.stereopsis.com/doubleblend.html
+ */
LLVMValueRef
lp_build_lerp(struct lp_build_context *bld,
LLVMValueRef x,
LLVMValueRef v0,
LLVMValueRef v1)
{
- return lp_build_add(bld, v0, lp_build_mul(bld, x, lp_build_sub(bld, v1, v0)));
+ LLVMValueRef delta;
+ LLVMValueRef res;
+
+ delta = lp_build_sub(bld, v1, v0);
+
+ res = lp_build_mul(bld, x, delta);
+
+ res = lp_build_add(bld, v0, res);
+
+ if(bld->type.fixed)
+ /* XXX: This step is necessary for lerping 8bit colors stored on 16bits,
+ * but it will be wrong for other uses. Basically we need a more
+ * powerful lp_type, capable of further distinguishing the values
+ * interpretation from the value storage. */
+ res = LLVMBuildAnd(bld->builder, res, lp_build_int_const_scalar(bld->type, (1 << bld->type.width/2) - 1), "");
+
+ return res;
}