[PATCH] D43063: [DAGCombiner] Call ExtendUsesToFormExtLoad in (zext (and (load)))->(and (zextload)) when the load has multiple uses not when the and has multiple uses.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, niravd.
Herald added a subscriber: jholewinski.
craig.topper added reviewers: jholewinski, tra.

Same for the sign extend case.

Currently we check for multiple uses on the binop. Then we call ExtendUsesToFormExtLoad to capture SetCCs that use the load. So we only end up finding any setccs when the and has additional uses and the load is used by a setcc. I don't think the and having multiple uses is relevant here. I think we should only be checking for the load having multiple uses.

This changes an NVPTX test because we now find that the load has a second use by a truncate, but ExtendUsesToFormExtLoad only looks at setccs it can extend. All other operations just check isTruncateFree. Maybe we should allow widening of an existing truncate even if its not free?

I'm also wondering if we need to check isTruncateFree for the truncate we introduce when the and/or/xor has additional users?


Repository:
  rL LLVM

https://reviews.llvm.org/D43063

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/NVPTX/param-load-store.ll


Index: test/CodeGen/NVPTX/param-load-store.ll
===================================================================
--- test/CodeGen/NVPTX/param-load-store.ll
+++ test/CodeGen/NVPTX/param-load-store.ll
@@ -23,10 +23,11 @@
 ; CHECK: .func  (.param .b32 func_retval0)
 ; CHECK-LABEL: test_i1(
 ; CHECK-NEXT: .param .b32 test_i1_param_0
-; CHECK:      ld.param.u8 [[A8:%r[0-9]+]], [test_i1_param_0];
-; CHECK:      and.b32 [[A:%r[0-9]+]], [[A8]], 1;
+; CHECK:      ld.param.u8 [[A8:%rs[0-9]+]], [test_i1_param_0];
+; CHECK:      and.b16 [[A:%rs[0-9]+]], [[A8]], 1;
+; CHECK:      cvt.u32.u16 [[B:%r[0-9]+]], [[A]]
 ; CHECK:      .param .b32 param0;
-; CHECK:      st.param.b32    [param0+0], [[A]]
+; CHECK:      st.param.b32    [param0+0], [[B]]
 ; CHECK:      .param .b32 retval0;
 ; CHECK:      call.uni
 ; CHECK-NEXT: test_i1,
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7610,7 +7610,7 @@
       LN00->getExtensionType() != ISD::ZEXTLOAD && LN00->isUnindexed()) {
       bool DoXform = true;
       SmallVector<SDNode*, 4> SetCCs;
-      if (!N0.hasOneUse())
+      if (!N0.getOperand(0).hasOneUse())
         DoXform = ExtendUsesToFormExtLoad(N, N0.getOperand(0), ISD::SIGN_EXTEND,
                                           SetCCs, TLI);
       if (DoXform) {
@@ -7913,10 +7913,10 @@
           if (isAndLoadExtLoad(AndC, LN00, LoadResultTy, ExtVT))
             DoXform = false;
         }
-        if (DoXform)
-          DoXform = ExtendUsesToFormExtLoad(N, N0.getOperand(0),
-                                            ISD::ZERO_EXTEND, SetCCs, TLI);
       }
+      if (DoXform && !N0.getOperand(0).hasOneUse())
+        DoXform = ExtendUsesToFormExtLoad(N, N0.getOperand(0),
+                                          ISD::ZERO_EXTEND, SetCCs, TLI);
       if (DoXform) {
         SDValue ExtLoad = DAG.getExtLoad(ISD::ZEXTLOAD, SDLoc(LN00), VT,
                                          LN00->getChain(), LN00->getBasePtr(),


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