[PATCH] D75808: [ValueTracking] isKnownNonZero, computeKnownBits for freeze

[Juneyoung Lee via Phabricator via llvm-commits]

This revision was not accepted when it landed; it landed in state "Needs Review".
This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGa6183d0f028c: [ValueTracking] isKnownNonZero, computeKnownBits for freeze (authored by aqjune).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D75808/new/

https://reviews.llvm.org/D75808

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/test/Transforms/InstSimplify/known-non-zero.ll
  llvm/unittests/Analysis/ValueTrackingTest.cpp


Index: llvm/unittests/Analysis/ValueTrackingTest.cpp
===================================================================
--- llvm/unittests/Analysis/ValueTrackingTest.cpp
+++ llvm/unittests/Analysis/ValueTrackingTest.cpp
@@ -1059,6 +1059,24 @@
   EXPECT_EQ(Known.One.getZExtValue(), 0u);
 }
 
+TEST_F(ComputeKnownBitsTest, ComputeKnownBitsFreeze) {
+  parseAssembly("define void @test() {\n"
+                "  %m = call i32 @any_num()\n"
+                "  %A = freeze i32 %m\n"
+                "  %n = and i32 %m, 31\n"
+                "  %c = icmp eq i32 %n, 0\n"
+                "  call void @llvm.assume(i1 %c)\n"
+                "  ret void\n"
+                "}\n"
+                "declare void @llvm.assume(i1)\n"
+                "declare i32 @any_num()\n");
+  AssumptionCache AC(*F);
+  KnownBits Known = computeKnownBits(A, M->getDataLayout(), /* Depth */ 0, &AC,
+                                     F->front().getTerminator());
+  EXPECT_EQ(Known.Zero.getZExtValue(), 31u);
+  EXPECT_EQ(Known.One.getZExtValue(), 0u);
+}
+
 class IsBytewiseValueTest : public ValueTrackingTest,
                             public ::testing::WithParamInterface<
                                 std::pair<const char *, const char *>> {
Index: llvm/test/Transforms/InstSimplify/known-non-zero.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/known-non-zero.ll
+++ llvm/test/Transforms/InstSimplify/known-non-zero.ll
@@ -145,3 +145,24 @@
   %inc = add nuw nsw i32 %shift.0, 1
   br label %for.cond
 }
+
+define i1 @freeze_nonzero(i8 %x, i8 %mask) {
+; CHECK-LABEL: @freeze_nonzero(
+; CHECK-NEXT:    [[Y:%.*]] = or i8 [[X:%.*]], [[MASK:%.*]]
+; CHECK-NEXT:    [[C:%.*]] = icmp ne i8 [[Y]], 0
+; CHECK-NEXT:    br i1 [[C]], label [[A:%.*]], label [[B:%.*]]
+; CHECK:       A:
+; CHECK-NEXT:    ret i1 false
+; CHECK:       B:
+; CHECK-NEXT:    ret i1 false
+;
+  %y = or i8 %x, %mask
+  %c = icmp ne i8 %y, 0
+  br i1 %c, label %A, label %B
+A:
+  %fr = freeze i8 %y
+  %c2 = icmp eq i8 %fr, 0
+  ret i1 %c2
+B:
+  ret i1 0
+}
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -1872,6 +1872,10 @@
       }
     }
     break;
+  case Instruction::Freeze:
+    if (isGuaranteedNotToBePoison(I->getOperand(0), Q.CxtI, Q.DT, Depth + 1))
+      computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
+    break;
   }
 }
 
@@ -2577,6 +2581,13 @@
       return isKnownNonZero(Vec, DemandedVecElts, Depth, Q);
     }
   }
+  // Freeze
+  else if (const FreezeInst *FI = dyn_cast<FreezeInst>(V)) {
+    auto *Op = FI->getOperand(0);
+    if (isKnownNonZero(Op, Depth, Q) &&
+        isGuaranteedNotToBePoison(Op, Q.CxtI, Q.DT, Depth))
+      return true;
+  }
 
   KnownBits Known(BitWidth);
   computeKnownBits(V, DemandedElts, Known, Depth, Q);


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