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InstSimplify: Optimize away pointless comparisons

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(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
This commit is contained in:
David Majnemer 2014-12-20 03:04:38 +00:00
parent 93e03df3cf
commit 9cd99a0724
3 changed files with 121 additions and 2 deletions
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7
include/llvm/IR/PatternMatch.h
View File

@ -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) {}

40
lib/Analysis/InstructionSimplify.cpp
View File

@ -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;

76
test/Transforms/InstSimplify/select.ll
View File

@ -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]]