[PATCH] D47878: [DAGCombiner] Fix for PR37667

[Sam Parker via Phabricator via llvm-commits]

samparker created this revision.
samparker added reviewers: spatel, niravd.

While trying to propagate AND masks back to loads, we currently allow one non-load node to be included as a leaf in chain. This fix now limits that node to produce only a single data value.


https://reviews.llvm.org/D47878

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/X86/pr37667.ll


Index: test/CodeGen/X86/pr37667.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/pr37667.ll
@@ -0,0 +1,26 @@
+; RUN: llc -O1 -mtriple=x86_64-unknown-linux-gnu %s -o - | FileCheck %s
+
+ at b = local_unnamed_addr global i32 918, align 4
+ at d = local_unnamed_addr global i32 8089, align 4
+ at c = common local_unnamed_addr global i32 0, align 4
+ at a = common local_unnamed_addr global i32 0, align 4
+
+; CHECK-LABEL: PR37667:
+; CHECK:  movl  b(%rip), %eax
+; CHECK:  xorl  %edx, %edx
+; CHECK:  divl  d(%rip)
+; CHECK:  orl c(%rip), %edx
+; CHECK:  movzbl  %dl, %eax
+; CHECK:  movl  %eax, a(%rip)
+; CHECK:  retq
+define void @PR37667() {
+  %t0 = load i32, i32* @c, align 4
+  %t1 = load i32, i32* @b, align 4
+  %t2 = load i32, i32* @d, align 4
+  %rem = urem i32 %t1, %t2
+  %or = or i32 %rem, %t0
+  %conv1 = and i32 %or, 255
+  store i32 %conv1, i32* @a, align 4
+  ret void
+}
+
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3997,7 +3997,22 @@
     // Allow one node which will masked along with any loads found.
     if (NodeToMask)
       return false;
+ 
+    // Also ensure that the node to be masked only produces one data result. 
     NodeToMask = Op.getNode();
+    if (NodeToMask->getNumValues() > 1) {
+      unsigned DataValues = 0;
+      for (unsigned i = 0; i < NodeToMask->getNumValues(); ++i) {
+        MVT VT = SDValue(NodeToMask, i).getSimpleValueType();
+        if (VT == MVT::Glue || VT == MVT::Other)
+          continue;
+        ++DataValues;
+      }
+      if (DataValues > 1) {
+        NodeToMask = nullptr;
+        return false;
+      }
+    }
   }
   return true;
 }


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