r600: double multiply can handle only one multiply at a time

It seems clear that trying to multiply two pairs of doubles would result
in the temporary register getting overwritten by the second pair. So
make the code more explicit.

Tested-by: Glenn Kennard <glenn.kennard@gmail.com>
Tested-by: James Harvey <lothmordor@gmail.com>
Cc: 17.0 <mesa-stable@lists.freedesktop.org>

diff --git a/src/gallium/drivers/r600/r600_shader.c b/src/gallium/drivers/r600/r600_shader.c
index ebe27445486dd7c7c9733163045dc1ec857b931b..7d1452add343bb88d473c9ebe0b5ba7c891eaa54 100644 (file)
--- a/src/gallium/drivers/r600/r600_shader.c
+++ b/src/gallium/drivers/r600/r600_shader.c
@@ -4326,25 +4326,27 @@ static int cayman_mul_double_instr(struct r600_shader_ctx *ctx)
        int lasti = tgsi_last_instruction(inst->Dst[0].Register.WriteMask);
        int t1 = ctx->temp_reg;
 
-       for (k = 0; k < 2; k++) {
-               if (!(inst->Dst[0].Register.WriteMask & (0x3 << (k * 2))))
-                       continue;
+       /* t1 would get overwritten below if we actually tried to
+        * multiply two pairs of doubles at a time. */
+       assert(inst->Dst[0].Register.WriteMask == TGSI_WRITEMASK_XY ||
+              inst->Dst[0].Register.WriteMask == TGSI_WRITEMASK_ZW);
 
-               for (i = 0; i < 4; i++) {
-                       memset(&alu, 0, sizeof(struct r600_bytecode_alu));
-                       alu.op = ctx->inst_info->op;
-                       for (j = 0; j < inst->Instruction.NumSrcRegs; j++) {
-                               r600_bytecode_src(&alu.src[j], &ctx->src[j], k * 2 + ((i == 3) ? 0 : 1));
-                       }
-                       alu.dst.sel = t1;
-                       alu.dst.chan = i;
-                       alu.dst.write = 1;
-                       if (i == 3)
-                               alu.last = 1;
-                       r = r600_bytecode_add_alu(ctx->bc, &alu);
-                       if (r)
-                               return r;
+       k = inst->Dst[0].Register.WriteMask == TGSI_WRITEMASK_XY ? 0 : 1;
+
+       for (i = 0; i < 4; i++) {
+               memset(&alu, 0, sizeof(struct r600_bytecode_alu));
+               alu.op = ctx->inst_info->op;
+               for (j = 0; j < inst->Instruction.NumSrcRegs; j++) {
+                       r600_bytecode_src(&alu.src[j], &ctx->src[j], k * 2 + ((i == 3) ? 0 : 1));
                }
+               alu.dst.sel = t1;
+               alu.dst.chan = i;
+               alu.dst.write = 1;
+               if (i == 3)
+                       alu.last = 1;
+               r = r600_bytecode_add_alu(ctx->bc, &alu);
+               if (r)
+                       return r;
        }
 
        for (i = 0; i <= lasti; i++) {