[Mesa-dev] [PATCH] nv50/ra: prefer def == src2 for mad/sad with immediates on nvc0

[Karol Herbst]

From: Karol Herbst <karolherbst at gmail.com>

This helps with the PostRALoadPropagation pass moving long immediates into
FMA/MAD instructions.

changes in shader-db:
total instructions in shared programs : 5894114 -> 5886074 (-0.14%)
total gprs used in shared programs    : 666558 -> 666563 (0.00%)
total shared used in shared programs  : 520416 -> 520416 (0.00%)
total local used in shared programs   : 53524 -> 53524 (0.00%)
total bytes used in shared programs   : 54006744 -> 53932472 (-0.14%)

                local     shared        gpr       inst      bytes
    helped           0           0           2        4192        4192
      hurt           0           0           7           9           9

Signed-off-by: Karol Herbst <karolherbst at gmail.com>
---
 src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp | 30 ++++++++++++++--------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
index 3a0e56e1385..aeaf1ebe8f0 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
@@ -1466,17 +1466,27 @@ GCRA::allocateRegisters(ArrayList& insns)
          nodes[i].init(regs, lval);
          RIG.insert(&nodes[i]);
 
-         if (lval->inFile(FILE_GPR) && lval->getInsn() != NULL &&
-             prog->getTarget()->getChipset() < 0xc0) {
+         if (lval->inFile(FILE_GPR) && lval->getInsn() != NULL) {
             Instruction *insn = lval->getInsn();
-            if (insn->op == OP_MAD || insn->op == OP_FMA || insn->op == OP_SAD)
-               // Short encoding only possible if they're all GPRs, no need to
-               // affect them otherwise.
-               if (insn->flagsDef < 0 &&
-                   insn->src(0).getFile() == FILE_GPR &&
-                   insn->src(1).getFile() == FILE_GPR &&
-                   insn->src(2).getFile() == FILE_GPR)
-                  nodes[i].addRegPreference(getNode(insn->getSrc(2)->asLValue()));
+            if (insn->op != OP_MAD && insn->op != OP_FMA && insn->op != OP_SAD)
+               continue;
+            // Short encoding or load propagate immediates only possible if
+            // they're all GPRs, no need to affect them otherwise.
+            if (insn->flagsDef >= 0 ||
+                insn->src(0).getFile() != FILE_GPR ||
+                insn->src(1).getFile() != FILE_GPR ||
+                insn->src(2).getFile() != FILE_GPR)
+               continue;
+            // for nvc0+ we can loadpropagate limms only if we have
+            // dest == src2 reg id. Using getImmediate here is fine because
+            // we only set a reg preference and leave the immediate alone.
+            ImmediateValue imm;
+            if (prog->getTarget()->getChipset() >= 0xc0 &&
+                !insn->src(0).getImmediate(imm) &&
+                !insn->src(1).getImmediate(imm))
+               continue;
+
+            nodes[i].addRegPreference(getNode(insn->getSrc(2)->asLValue()));
          }
       }
    }
-- 
2.14.3