i915: fix broken indirect constant buffer reads

The READ message's msg_control value can be 0 or 1 to indicate that the
Oword should be read into the lower or upper half of the target register.
It seems that the other half of the register gets clobbered though.  So
we read into two dest registers then use a MOV to combine the upper/lower
halves.

1 files changed, 36 insertions, 7 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_vs_emit.c b/src/mesa/drivers/dri/i965/brw_vs_emit.c
index 0c86c23ad9..524f1211ce 100644
--- a/src/mesa/drivers/dri/i965/brw_vs_emit.c
+++ b/src/mesa/drivers/dri/i965/brw_vs_emit.c
@@ -708,10 +708,12 @@ get_constant(struct brw_vs_compile *c,
    const struct prog_src_register *src = &inst->SrcReg[argIndex];
    struct brw_compile *p = &c->func;
    struct brw_reg const_reg;
+   struct brw_reg const2_reg;
 
    assert(argIndex < 3);
 
    if (c->current_const[argIndex].index != src->Index || src->RelAddr) {
+      struct brw_reg addrReg = c->regs[PROGRAM_ADDRESS][0];
 
       c->current_const[argIndex].index = src->Index;
 
@@ -719,19 +721,46 @@ get_constant(struct brw_vs_compile *c,
       printf("  fetch const[%d] for arg %d into reg %d\n",
              src->Index, argIndex, c->current_const[argIndex].reg.nr);
 #endif
-
       /* need to fetch the constant now */
       brw_dp_READ_4_vs(p,
-                       c->current_const[argIndex].reg, /* writeback dest */
-                       src->RelAddr,                   /* relative indexing? */
-                       c->regs[PROGRAM_ADDRESS][0],    /* address register */
-                       16 * src->Index,                /* byte offset */
-                       SURF_INDEX_VERT_CONST_BUFFER    /* binding table index */
+                       c->current_const[argIndex].reg,/* writeback dest */
+                       0,                             /* oword */
+                       src->RelAddr,                  /* relative indexing? */
+                       addrReg,                       /* address register */
+                       16 * src->Index,               /* byte offset */
+                       SURF_INDEX_VERT_CONST_BUFFER   /* binding table index */
                        );
+
+      if (src->RelAddr) {
+         /* second read */
+         const2_reg = get_tmp(c);
+
+         /* use upper half of address reg for second read */
+         addrReg = stride(addrReg, 0, 4, 0);
+         addrReg.subnr = 16;
+
+         brw_dp_READ_4_vs(p,
+                          const2_reg,              /* writeback dest */
+                          1,                       /* oword */
+                          src->RelAddr,            /* relative indexing? */
+                          addrReg,                 /* address register */
+                          16 * src->Index,         /* byte offset */
+                          SURF_INDEX_VERT_CONST_BUFFER
+                          );
+      }
    }
 
    const_reg = c->current_const[argIndex].reg;
-   if (!src->RelAddr) {
+
+   if (src->RelAddr) {
+      /* merge the two Owords into the constant register */
+      /* const_reg[7..4] = const2_reg[7..4] */
+      brw_MOV(p,
+              suboffset(stride(const_reg, 0, 4, 1), 4),
+              suboffset(stride(const2_reg, 0, 4, 1), 4));
+      release_tmp(c, const2_reg);
+   }
+   else {
       /* replicate lower four floats into upper half (to get XYZWXYZW) */
       const_reg = stride(const_reg, 0, 4, 0);
       const_reg.subnr = 0;