InstSimplify: Optimize away pointless comparisons

(X & INT_MIN) ? X & INT_MAX : X  into  X & INT_MAX
(X & INT_MIN) ? X : X & INT_MAX  into  X
(X & INT_MIN) ? X | INT_MIN : X  into  X
(X & INT_MIN) ? X : X | INT_MIN  into  X | INT_MIN

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224669 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/IR/PatternMatch.h b/include/llvm/IR/PatternMatch.h
index 1152af9239493d5159daad6e62166129ef361175..f94e10576893310c24fd967e59f0ba8cc9161b05 100644 (file)
--- a/include/llvm/IR/PatternMatch.h
+++ b/include/llvm/IR/PatternMatch.h
@@ -272,6 +272,13 @@ struct is_power2 {
 inline cst_pred_ty<is_power2> m_Power2() { return cst_pred_ty<is_power2>(); }
 inline api_pred_ty<is_power2> m_Power2(const APInt *&V) { return V; }
 
+struct is_maxsignedvalue {
+  bool isValue(const APInt &C) { return C.isMaxSignedValue(); }
+};
+
+inline cst_pred_ty<is_maxsignedvalue> m_MaxSignedValue() { return cst_pred_ty<is_maxsignedvalue>(); }
+inline api_pred_ty<is_maxsignedvalue> m_MaxSignedValue(const APInt *&V) { return V; }
+
 template <typename Class> struct bind_ty {
   Class *&VR;
   bind_ty(Class *&V) : VR(V) {}

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 1db7ab7bf0356c0df1800141170e226f7b00397f..b7882651d36f7362df330baa143249deaf3522a4 100644 (file)
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -3155,10 +3155,10 @@ static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal,
   if (const auto *ICI = dyn_cast<ICmpInst>(CondVal)) {
     Value *X;
     const APInt *Y;
-    if (ICI->isEquality() &&
+    ICmpInst::Predicate Pred = ICI->getPredicate();
+    if (ICmpInst::isEquality(Pred) &&
         match(ICI->getOperand(0), m_And(m_Value(X), m_APInt(Y))) &&
         match(ICI->getOperand(1), m_Zero())) {
-      ICmpInst::Predicate Pred = ICI->getPredicate();
       const APInt *C;
       // (X & Y) == 0 ? X & ~Y : X  --> X
       // (X & Y) != 0 ? X & ~Y : X  --> X & ~Y
@@ -3184,6 +3184,42 @@ static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal,
           return Pred == ICmpInst::ICMP_EQ ? TrueVal : FalseVal;
       }
     }
+    if (Pred == ICmpInst::ICMP_SLT && match(ICI->getOperand(1), m_Zero())) {
+      // (X < 0) ? X : X | SignBit  --> X | SignBit
+      if (TrueVal == ICI->getOperand(0) &&
+          match(FalseVal, m_Or(m_Specific(TrueVal), m_SignBit())))
+        return FalseVal;
+      // (X < 0) ? X | SignBit : X  --> X
+      if (FalseVal == ICI->getOperand(0) &&
+          match(TrueVal, m_Or(m_Specific(FalseVal), m_SignBit())))
+        return FalseVal;
+      // (X < 0) ? X & INT_MAX : X  --> X & INT_MAX
+      if (FalseVal == ICI->getOperand(0) &&
+          match(TrueVal, m_And(m_Specific(FalseVal), m_MaxSignedValue())))
+        return TrueVal;
+      // (X < 0) ? X : X & INT_MAX  --> X
+      if (TrueVal == ICI->getOperand(0) &&
+          match(FalseVal, m_And(m_Specific(TrueVal), m_MaxSignedValue())))
+        return TrueVal;
+    }
+    if (Pred == ICmpInst::ICMP_SGT && match(ICI->getOperand(1), m_AllOnes())) {
+      // (X > -1) ? X : X | SignBit  --> X
+      if (TrueVal == ICI->getOperand(0) &&
+          match(FalseVal, m_Or(m_Specific(TrueVal), m_SignBit())))
+        return TrueVal;
+      // (X > -1) ? X | SignBit : X  --> X | SignBit
+      if (FalseVal == ICI->getOperand(0) &&
+          match(TrueVal, m_Or(m_Specific(FalseVal), m_SignBit())))
+        return TrueVal;
+      // (X > -1) ? X & INT_MAX : X  --> X
+      if (FalseVal == ICI->getOperand(0) &&
+          match(TrueVal, m_And(m_Specific(FalseVal), m_MaxSignedValue())))
+        return FalseVal;
+      // (X > -1) ? X : X & INT_MAX  --> X & INT_MAX
+      if (TrueVal == ICI->getOperand(0) &&
+          match(FalseVal, m_And(m_Specific(TrueVal), m_MaxSignedValue())))
+        return FalseVal;
+    }
   }
 
   return nullptr;

diff --git a/test/Transforms/InstSimplify/select.ll b/test/Transforms/InstSimplify/select.ll
index b30416e9d265d476167b869cd543a1710b68e821..1d45e5728e687a60771e0dcc24fb0e10984aa1ae 100644 (file)
--- a/test/Transforms/InstSimplify/select.ll
+++ b/test/Transforms/InstSimplify/select.ll
@@ -31,6 +31,82 @@ define i32 @test3(i32 %x) {
 ; CHECK: ret i32 %[[and]]
 }
 
+define i32 @test4(i32 %X) {
+  %cmp = icmp slt i32 %X, 0
+  %or = or i32 %X, -2147483648
+  %cond = select i1 %cmp, i32 %X, i32 %or
+  ret i32 %cond
+; CHECK-LABEL: @test4
+; CHECK: %[[or:.*]] = or i32 %X, -2147483648
+; CHECK: ret i32 %[[or]]
+}
+
+define i32 @test5(i32 %X) {
+  %cmp = icmp slt i32 %X, 0
+  %or = or i32 %X, -2147483648
+  %cond = select i1 %cmp, i32 %or, i32 %X
+  ret i32 %cond
+; CHECK-LABEL: @test5
+; CHECK: ret i32 %X
+}
+
+define i32 @test6(i32 %X) {
+  %cmp = icmp slt i32 %X, 0
+  %and = and i32 %X, 2147483647
+  %cond = select i1 %cmp, i32 %and, i32 %X
+  ret i32 %cond
+; CHECK-LABEL: @test6
+; CHECK: %[[and:.*]] = and i32 %X, 2147483647
+; CHECK: ret i32 %[[and]]
+}
+
+define i32 @test7(i32 %X) {
+  %cmp = icmp slt i32 %X, 0
+  %and = and i32 %X, 2147483647
+  %cond = select i1 %cmp, i32 %X, i32 %and
+  ret i32 %cond
+; CHECK-LABEL: @test7
+; CHECK: ret i32 %X
+}
+
+define i32 @test8(i32 %X) {
+  %cmp = icmp sgt i32 %X, -1
+  %or = or i32 %X, -2147483648
+  %cond = select i1 %cmp, i32 %X, i32 %or
+  ret i32 %cond
+; CHECK-LABEL: @test8
+; CHECK: ret i32 %X
+}
+
+define i32 @test9(i32 %X) {
+  %cmp = icmp sgt i32 %X, -1
+  %or = or i32 %X, -2147483648
+  %cond = select i1 %cmp, i32 %or, i32 %X
+  ret i32 %cond
+; CHECK-LABEL: @test9
+; CHECK: %[[or:.*]] = or i32 %X, -2147483648
+; CHECK: ret i32 %[[or]]
+}
+
+define i32 @test10(i32 %X) {
+  %cmp = icmp sgt i32 %X, -1
+  %and = and i32 %X, 2147483647
+  %cond = select i1 %cmp, i32 %and, i32 %X
+  ret i32 %cond
+; CHECK-LABEL: @test10
+; CHECK: ret i32 %X
+}
+
+define i32 @test11(i32 %X) {
+  %cmp = icmp sgt i32 %X, -1
+  %and = and i32 %X, 2147483647
+  %cond = select i1 %cmp, i32 %X, i32 %and
+  ret i32 %cond
+; CHECK-LABEL: @test11
+; CHECK: %[[and:.*]] = and i32 %X, 2147483647
+; CHECK: ret i32 %[[and]]
+}
+
 ; CHECK-LABEL: @select_icmp_and_8_eq_0_or_8(
 ; CHECK-NEXT: [[OR:%[a-z0-9]+]] = or i32 %x, 8
 ; CHECK-NEXT: ret i32 [[OR]]