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Teach instruction simplify to use constant ranges to solve problems of the form
"icmp pred %X, CI" and a number of examples where "%X = binop %Y, CI2". Some of these cases (div and rem) used to make it through opt -O2, but the others are probably now making code elsewhere redundant (probably instcombine). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126988 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -23,6 +23,7 @@
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#include "llvm/Analysis/ConstantFolding.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/Support/ConstantRange.h"
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#include "llvm/Support/PatternMatch.h"
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#include "llvm/Support/ValueHandle.h"
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#include "llvm/Target/TargetData.h"
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@ -1399,44 +1400,67 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
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// See if we are doing a comparison with a constant integer.
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if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
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switch (Pred) {
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default: break;
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case ICmpInst::ICMP_UGT:
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if (CI->isMaxValue(false)) // A >u MAX -> FALSE
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return ConstantInt::getFalse(CI->getContext());
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break;
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case ICmpInst::ICMP_UGE:
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if (CI->isMinValue(false)) // A >=u MIN -> TRUE
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return ConstantInt::getTrue(CI->getContext());
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break;
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case ICmpInst::ICMP_ULT:
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if (CI->isMinValue(false)) // A <u MIN -> FALSE
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return ConstantInt::getFalse(CI->getContext());
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break;
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case ICmpInst::ICMP_ULE:
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if (CI->isMaxValue(false)) // A <=u MAX -> TRUE
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return ConstantInt::getTrue(CI->getContext());
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break;
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case ICmpInst::ICMP_SGT:
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if (CI->isMaxValue(true)) // A >s MAX -> FALSE
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return ConstantInt::getFalse(CI->getContext());
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break;
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case ICmpInst::ICMP_SGE:
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if (CI->isMinValue(true)) // A >=s MIN -> TRUE
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return ConstantInt::getTrue(CI->getContext());
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break;
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case ICmpInst::ICMP_SLT:
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if (CI->isMinValue(true)) // A <s MIN -> FALSE
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return ConstantInt::getFalse(CI->getContext());
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break;
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case ICmpInst::ICMP_SLE:
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if (CI->isMaxValue(true)) // A <=s MAX -> TRUE
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return ConstantInt::getTrue(CI->getContext());
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break;
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}
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// Rule out tautological comparisons (eg., ult 0 or uge 0).
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ConstantRange RHS_CR = ICmpInst::makeConstantRange(Pred, CI->getValue());
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if (RHS_CR.isEmptySet())
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return ConstantInt::getFalse(CI->getContext());
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if (RHS_CR.isFullSet())
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return ConstantInt::getTrue(CI->getContext());
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// TODO: integer div and rem with constant RHS all produce values in a
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// constant range. We should check whether the comparison is a tautology.
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// Many binary operators with constant RHS have easy to compute constant
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// range. Use them to check whether the comparison is a tautology.
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uint32_t Width = CI->getBitWidth();
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APInt Lower = APInt(Width, 0);
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APInt Upper = APInt(Width, 0);
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ConstantInt *CI2;
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if (match(LHS, m_URem(m_Value(), m_ConstantInt(CI2)))) {
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// 'urem x, CI2' produces [0, CI2).
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Upper = CI2->getValue();
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} else if (match(LHS, m_SRem(m_Value(), m_ConstantInt(CI2)))) {
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// 'srem x, CI2' produces (-|CI2|, |CI2|).
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Upper = CI2->getValue().abs();
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Lower = (-Upper) + 1;
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} else if (match(LHS, m_UDiv(m_Value(), m_ConstantInt(CI2)))) {
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// 'udiv x, CI2' produces [0, UINT_MAX / CI2].
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APInt NegOne = APInt::getAllOnesValue(Width);
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if (!CI2->isZero())
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Upper = NegOne.udiv(CI2->getValue()) + 1;
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} else if (match(LHS, m_SDiv(m_Value(), m_ConstantInt(CI2)))) {
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// 'sdiv x, CI2' produces [INT_MIN / CI2, INT_MAX / CI2].
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APInt IntMin = APInt::getSignedMinValue(Width);
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APInt IntMax = APInt::getSignedMaxValue(Width);
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APInt Val = CI2->getValue().abs();
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if (!Val.isMinValue()) {
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Lower = IntMin.sdiv(Val);
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Upper = IntMax.sdiv(Val) + 1;
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}
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} else if (match(LHS, m_LShr(m_Value(), m_ConstantInt(CI2)))) {
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// 'lshr x, CI2' produces [0, UINT_MAX >> CI2].
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APInt NegOne = APInt::getAllOnesValue(Width);
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if (CI2->getValue().ult(Width))
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Upper = NegOne.lshr(CI2->getValue()) + 1;
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} else if (match(LHS, m_AShr(m_Value(), m_ConstantInt(CI2)))) {
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// 'ashr x, CI2' produces [INT_MIN >> CI2, INT_MAX >> CI2].
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APInt IntMin = APInt::getSignedMinValue(Width);
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APInt IntMax = APInt::getSignedMaxValue(Width);
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if (CI2->getValue().ult(Width)) {
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Lower = IntMin.ashr(CI2->getValue());
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Upper = IntMax.ashr(CI2->getValue()) + 1;
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}
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} else if (match(LHS, m_Or(m_Value(), m_ConstantInt(CI2)))) {
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// 'or x, CI2' produces [CI2, UINT_MAX].
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Lower = CI2->getValue();
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} else if (match(LHS, m_And(m_Value(), m_ConstantInt(CI2)))) {
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// 'and x, CI2' produces [0, CI2].
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Upper = CI2->getValue() + 1;
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}
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if (Lower != Upper) {
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ConstantRange LHS_CR = ConstantRange(Lower, Upper);
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if (RHS_CR.contains(LHS_CR))
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return ConstantInt::getTrue(RHS->getContext());
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if (RHS_CR.inverse().contains(LHS_CR))
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return ConstantInt::getFalse(RHS->getContext());
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}
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}
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// Compare of cast, for example (zext X) != 0 -> X != 0
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@ -137,22 +137,38 @@ define i1 @shl(i32 %x) {
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; CHECK: ret i1 false
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}
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define i1 @lshr(i32 %x) {
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; CHECK: @lshr
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define i1 @lshr1(i32 %x) {
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; CHECK: @lshr1
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%s = lshr i32 -1, %x
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%c = icmp eq i32 %s, 0
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ret i1 %c
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; CHECK: ret i1 false
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}
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define i1 @ashr(i32 %x) {
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; CHECK: @ashr
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define i1 @lshr2(i32 %x) {
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; CHECK: @lshr2
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%s = lshr i32 %x, 30
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%c = icmp ugt i32 %s, 8
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ret i1 %c
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; CHECK: ret i1 false
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}
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define i1 @ashr1(i32 %x) {
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; CHECK: @ashr1
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%s = ashr i32 -1, %x
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%c = icmp eq i32 %s, 0
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ret i1 %c
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; CHECK: ret i1 false
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}
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define i1 @ashr2(i32 %x) {
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; CHECK: @ashr2
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%s = ashr i32 %x, 30
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%c = icmp slt i32 %s, -5
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ret i1 %c
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; CHECK: ret i1 false
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}
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define i1 @select1(i1 %cond) {
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; CHECK: @select1
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%s = select i1 %cond, i32 1, i32 0
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@ -203,3 +219,59 @@ define i1 @urem2(i32 %X, i32 %Y) {
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ret i1 %B
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; CHECK ret i1 false
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}
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define i1 @urem3(i32 %X) {
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; CHECK: @urem3
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%A = urem i32 %X, 10
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%B = icmp ult i32 %A, 15
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ret i1 %B
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; CHECK: ret i1 true
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}
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define i1 @urem4(i32 %X) {
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; CHECK: @urem4
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%A = urem i32 %X, 15
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%B = icmp ult i32 %A, 10
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ret i1 %B
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; CHECK: ret i1 %B
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}
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define i1 @srem1(i32 %X) {
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; CHECK: @srem1
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%A = srem i32 %X, -5
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%B = icmp sgt i32 %A, 5
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ret i1 %B
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; CHECK: ret i1 false
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}
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define i1 @udiv1(i32 %X) {
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; CHECK: @udiv1
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%A = udiv i32 %X, 1000000
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%B = icmp ult i32 %A, 5000
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ret i1 %B
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; CHECK: ret i1 true
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}
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define i1 @sdiv1(i32 %X) {
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; CHECK: @sdiv1
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%A = sdiv i32 %X, 1000000
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%B = icmp slt i32 %A, 3000
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ret i1 %B
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; CHECK: ret i1 true
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}
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define i1 @or1(i32 %X) {
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; CHECK: @or1
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%A = or i32 %X, 62
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%B = icmp ult i32 %A, 50
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ret i1 %B
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; CHECK: ret i1 false
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}
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define i1 @and1(i32 %X) {
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; CHECK: @and1
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%A = and i32 %X, 62
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%B = icmp ugt i32 %A, 70
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ret i1 %B
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; CHECK: ret i1 false
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}
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