Mesa (7.9): r300/compiler: Ignore alpha dest register when replicating the result

[Tom Stellard]

Module: Mesa
Branch: 7.9
Commit: 5551faf6498fafd7f280b7697ab0dba3b7411269
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=5551faf6498fafd7f280b7697ab0dba3b7411269

Author: Tom Stellard <tstellar at gmail.com>
Date:   Thu Nov 11 01:13:01 2010 -0800

r300/compiler: Ignore alpha dest register when replicating the result

When the result of the alpha instruction is being replicated to the RGB
destination register, we do not need to use alpha's destination register.
This fixes an invalid "Too many hardware temporaries used" error in
the case where a transcendent operation writes to a temporary register
greater than max_temp_regs.

NOTE: This is a candidate for the 7.9 branch.
(cherry picked from commit 23f577dbd491bd045c47c6378bd23748255eb045)

---

 .../dri/r300/compiler/radeon_pair_translate.c      |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/src/mesa/drivers/dri/r300/compiler/radeon_pair_translate.c b/src/mesa/drivers/dri/r300/compiler/radeon_pair_translate.c
index ff82584..840c7a5 100644
--- a/src/mesa/drivers/dri/r300/compiler/radeon_pair_translate.c
+++ b/src/mesa/drivers/dri/r300/compiler/radeon_pair_translate.c
@@ -278,9 +278,12 @@ static void set_pair_instruction(struct r300_fragment_program_compiler *c,
 			pair->RGB.DestIndex = inst->DstReg.Index;
 			pair->RGB.WriteMask |= inst->DstReg.WriteMask & RC_MASK_XYZ;
 		}
+
 		if (needalpha) {
-			pair->Alpha.DestIndex = inst->DstReg.Index;
 			pair->Alpha.WriteMask |= GET_BIT(inst->DstReg.WriteMask, 3);
+			if (pair->Alpha.WriteMask) {
+				pair->Alpha.DestIndex = inst->DstReg.Index;
+			}
 		}
 	}