[Mesa-dev] [RFC 20/24] nvc0/ir: prevent out of bounds when no images are bound

[Samuel Pitoiset]

Checking if the image address is not 0 should be enough to prevent
read faults. To improve robustness, make sure that the destination
value of atomic operations is correctly initialized in case the
instruction is not performed.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
---
 .../drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
index bd7e4bd..253084e 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
@@ -1774,6 +1774,13 @@ NVC0LoweringPass::processSurfaceCoordsNVE4(TexInstruction *su)
    su->setSrc(0, addr);
    su->setSrc(1, v);
    su->setSrc(2, pred);
+
+   // prevent read fault when the image is not actually bound
+   CmpInstruction *pred1 =
+      bld.mkCmp(OP_SET, CC_EQ, TYPE_U32, bld.getSSA(1, FILE_PREDICATE),
+                TYPE_U32, bld.mkImm(0),
+                loadSuInfo32(ind, base + NVE4_SU_INFO_ADDR));
+   su->setPredicate(CC_NOT_P, pred1->getDef(0));
 }
 
 static DataType
@@ -1893,7 +1900,6 @@ NVC0LoweringPass::handleSurfaceOpNVE4(TexInstruction *su)
       convertSurfaceFormat(su);
 
    if (su->op == OP_SUREDB || su->op == OP_SUREDP) {
-      // FIXME: for out of bounds access, destination value will be undefined !
       Value *pred = su->getSrc(2);
       CondCode cc = CC_NOT_P;
       if (su->getPredicate()) {
@@ -1915,7 +1921,18 @@ NVC0LoweringPass::handleSurfaceOpNVE4(TexInstruction *su)
       if (su->subOp == NV50_IR_SUBOP_ATOM_CAS)
          red->setSrc(2, su->getSrc(4));
       red->setIndirect(0, 0, su->getSrc(0));
+
+      // make sure to initialize dst value when the atomic operation is not
+      // performed
+      Instruction *mov = bld.mkMov(bld.getScratch(), bld.loadImm(NULL, 0));
+
+      assert(cc == CC_NOT_P);
       red->setPredicate(cc, pred);
+      mov->setPredicate(CC_P, pred);
+
+      bld.mkOp2(OP_UNION, TYPE_U32, su->getDef(0),
+                red->getDef(0), mov->getDef(0));
+
       delete_Instruction(bld.getProgram(), su);
       handleCasExch(red, true);
    }
-- 
2.8.0