[Mesa-dev] [PATCH v2] nv50/ir: make a copy of tex src if it's referenced multiple times

[Ilia Mirkin]

For nv50 we coalesce the srcs and defs into a single node. As such, we
can end up with impossible constraints if the source is referenced
after the tex operation (which, due to the coalescing of values, will
have overwritten it).

This logic already exists for inserting moves for MERGE/UNION sources.
It's the exact same idea here, so leverage that code, which also
includes a few optimizations around not extending live ranges
unnecessarily.

Signed-off-by: Ilia Mirkin <imir...@alum.mit.edu>
---

v1 -> v2: make use of existing logic in insertConstraintMoves

 src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp | 86 ++++++++++++----------
 1 file changed, 49 insertions(+), 37 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..7d107aca68d 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
@@ -257,6 +257,7 @@ private:
    private:
       virtual bool visit(BasicBlock *);
 
+      void insertConstraintMove(Instruction *, int s);
       bool insertConstraintMoves();
 
       void condenseDefs(Instruction *);
@@ -2216,6 +2217,8 @@ 
RegAlloc::InsertConstraintsPass::texConstraintNV50(TexInstruction *tex)
    for (c = 0; tex->srcExists(c) || tex->defExists(c); ++c) {
       if (!tex->srcExists(c))
          tex->setSrc(c, new_LValue(func, tex->getSrc(0)->asLValue()));
+      else
+         insertConstraintMove(tex, c);
       if (!tex->defExists(c))
          tex->setDef(c, new_LValue(func, tex->getDef(0)->asLValue()));
    }
@@ -2288,6 +2291,51 @@ RegAlloc::InsertConstraintsPass::visit(BasicBlock *bb)
    return true;
 }
 
+void
+RegAlloc::InsertConstraintsPass::insertConstraintMove(Instruction *cst, int s)
+{
+   const uint8_t size = cst->src(s).getSize();
+
+   assert(cst->getSrc(s)->defs.size() == 1); // still SSA
+
+   Instruction *defi = cst->getSrc(s)->defs.front()->getInsn();
+   bool imm = defi->op == OP_MOV &&
+      defi->src(0).getFile() == FILE_IMMEDIATE;
+   bool load = defi->op == OP_LOAD &&
+      defi->src(0).getFile() == FILE_MEMORY_CONST &&
+      !defi->src(0).isIndirect(0);
+   // catch some cases where don't really need MOVs
+   if (cst->getSrc(s)->refCount() == 1 && !defi->constrainedDefs()) {
+      if (imm || load) {
+         // Move the defi right before the cst. No point in expanding
+         // the range.
+         defi->bb->remove(defi);
+         cst->bb->insertBefore(cst, defi);
+      }
+      return;
+   }
+
+   LValue *lval = new_LValue(func, cst->src(s).getFile());
+   lval->reg.size = size;
+
+   Instruction *mov = new_Instruction(func, OP_MOV, typeOfSize(size));
+   mov->setDef(0, lval);
+   mov->setSrc(0, cst->getSrc(s));
+
+   if (load) {
+      mov->op = OP_LOAD;
+      mov->setSrc(0, defi->getSrc(0));
+   } else if (imm) {
+      mov->setSrc(0, defi->getSrc(0));
+   }
+
+   if (defi->getPredicate())
+      mov->setPredicate(defi->cc, defi->getPredicate());
+
+   cst->setSrc(s, mov->getDef(0));
+   cst->bb->insertBefore(cst, mov);
+}
+
 // Insert extra moves so that, if multiple register constraints on a value are
 // in conflict, these conflicts can be resolved.
 bool
@@ -2328,46 +2376,10 @@ RegAlloc::InsertConstraintsPass::insertConstraintMoves()
                cst->bb->insertBefore(cst, mov);
                continue;
             }
-            assert(cst->getSrc(s)->defs.size() == 1); // still SSA
-
-            Instruction *defi = cst->getSrc(s)->defs.front()->getInsn();
-            bool imm = defi->op == OP_MOV &&
-               defi->src(0).getFile() == FILE_IMMEDIATE;
-            bool load = defi->op == OP_LOAD &&
-               defi->src(0).getFile() == FILE_MEMORY_CONST &&
-               !defi->src(0).isIndirect(0);
-            // catch some cases where don't really need MOVs
-            if (cst->getSrc(s)->refCount() == 1 && !defi->constrainedDefs()) {
-               if (imm || load) {
-                  // Move the defi right before the cst. No point in expanding
-                  // the range.
-                  defi->bb->remove(defi);
-                  cst->bb->insertBefore(cst, defi);
-               }
-               continue;
-            }
 
-            LValue *lval = new_LValue(func, cst->src(s).getFile());
-            lval->reg.size = size;
-
-            mov = new_Instruction(func, OP_MOV, typeOfSize(size));
-            mov->setDef(0, lval);
-            mov->setSrc(0, cst->getSrc(s));
-
-            if (load) {
-               mov->op = OP_LOAD;
-               mov->setSrc(0, defi->getSrc(0));
-            } else if (imm) {
-               mov->setSrc(0, defi->getSrc(0));
-            }
-
-            cst->setSrc(s, mov->getDef(0));
-            cst->bb->insertBefore(cst, mov);
+            insertConstraintMove(cst, s);
 
             cst->getDef(0)->asLValue()->noSpill = 1; // doesn't help
-
-            if (cst->op == OP_UNION)
-               mov->setPredicate(defi->cc, defi->getPredicate());
          }
       }
    }
-- 
2.16.1

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