r300: Turn a comment about presub into an assert.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14092>

diff --git a/src/gallium/drivers/r300/compiler/radeon_optimize.c b/src/gallium/drivers/r300/compiler/radeon_optimize.c
index 5e3503b..df95684 100644 (file)
--- a/src/gallium/drivers/r300/compiler/radeon_optimize.c
+++ b/src/gallium/drivers/r300/compiler/radeon_optimize.c
@@ -496,14 +496,18 @@ static int presub_helper(
        return 1;
 }
 
-/* This function assumes that inst_add->U.I.SrcReg[0] and
- * inst_add->U.I.SrcReg[1] aren't both negative. */
 static void presub_replace_add(
        struct rc_instruction * inst_add,
        struct rc_instruction * inst_reader,
        unsigned int src_index)
 {
        rc_presubtract_op presub_opcode;
+
+       /* This function assumes that inst_add->U.I.SrcReg[0] and
+        * inst_add->U.I.SrcReg[1] aren't both negative.
+        */
+       assert(!(inst_add->U.I.SrcReg[1].Negate && inst_add->U.I.SrcReg[0].Negate));
+
        if (inst_add->U.I.SrcReg[1].Negate || inst_add->U.I.SrcReg[0].Negate)
                presub_opcode = RC_PRESUB_SUB;
        else