diff --git a/src/gallium/drivers/r300/compiler/r3xx_fragprog.c b/src/gallium/drivers/r300/compiler/r3xx_fragprog.c
index 556a16a2e0d..67680915226 100644
--- a/src/gallium/drivers/r300/compiler/r3xx_fragprog.c
+++ b/src/gallium/drivers/r300/compiler/r3xx_fragprog.c
@@ -30,6 +30,8 @@
 #include "radeon_program_tex.h"
 #include "radeon_rename_regs.h"
 #include "radeon_remove_constants.h"
+#include "radeon_variable.h"
+#include "radeon_list.h"
 #include "r300_fragprog.h"
 #include "r300_fragprog_swizzle.h"
 #include "r500_fragprog.h"
@@ -65,6 +67,48 @@ static void rc_rewrite_depth_out(struct radeon_compiler *cc, void *user)
 	}
 }
 
+/**
+ * This function will try to convert rgb instructions into alpha instructions
+ * and vice versa. While this is already attempted during the pair scheduling,
+ * it is much simpler to do it before pair conversion, so do it here at least for
+ * the simple cases.
+ *
+ * Currently only math opcodes writing to rgb (and with no friends) are
+ * converted to alpha.
+ *
+ * This function assumes all the instructions are still of type
+ * RC_INSTRUCTION_NORMAL, the conversion is much simpler.
+ *
+ * Beware that this needs to be also called before doing presubtract, because
+ * rc_get_variables can't get properly readers for normal instructions if presubtract
+ * is present (it works fine for pair instructions).
+ */
+static void rc_convert_rgb_alpha(struct radeon_compiler *c, void *user)
+{
+	struct rc_list * variables;
+	struct rc_list * var_ptr;
+
+	variables = rc_get_variables(c);
+
+	for (var_ptr = variables; var_ptr; var_ptr = var_ptr->Next) {
+		struct rc_variable * var = var_ptr->Item;
+
+		if (var->Inst->U.I.DstReg.File != RC_FILE_TEMPORARY) {
+			continue;
+		}
+
+		/* Only rewrite scalar opcodes that are used separatelly for now. */
+		if (var->Friend)
+			continue;
+
+		const struct rc_opcode_info * opcode = rc_get_opcode_info(var->Inst->U.I.Opcode);
+		if (opcode->IsStandardScalar && var->Dst.WriteMask != RC_MASK_W) {
+			unsigned index = rc_find_free_temporary(c);
+			rc_variable_change_dst(var, index, RC_MASK_W);
+		}
+	}
+}
+
 void r3xx_compile_fragment_program(struct r300_fragment_program_compiler* c)
 {
 	int is_r500 = c->Base.is_r500;
@@ -104,6 +148,7 @@ void r3xx_compile_fragment_program(struct r300_fragment_program_compiler* c)
 		{"native rewrite",		1, is_r500,	rc_local_transform,		native_rewrite_r500},
 		{"native rewrite",		1, !is_r500,	rc_local_transform,		native_rewrite_r300},
 		{"deadcode",			1, opt,		rc_dataflow_deadcode,		NULL},
+		{"convert rgb<->alpha",		1, opt,		rc_convert_rgb_alpha,		NULL},
 		{"register rename",		1, !is_r500 || opt,		rc_rename_regs,			NULL},
 		{"dataflow optimize",		1, opt,		rc_optimize,			NULL},
 		{"inline literals",		1, is_r500 && opt,		rc_inline_literals,			NULL},