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give instcombine some helper functions for matching MIN and MAX, and

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implement some optimizations for MIN(MIN()) and MAX(MAX()) and 
MIN(MAX()) etc.  This substantially improves the code in PR5822 but
doesn't kick in much elsewhere.  2 max's were optimized in 
pairlocalalign and one in smg2000.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91814 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-12-21 06:03:05 +00:00
parent a278d4a1f7
commit b109b5c148
2 changed files with 158 additions and 10 deletions
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128
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -75,6 +75,15 @@ STATISTIC(NumDeadInst , "Number of dead inst eliminated");
STATISTIC(NumDeadStore, "Number of dead stores eliminated");
STATISTIC(NumSunkInst , "Number of instructions sunk");
/// SelectPatternFlavor - We can match a variety of different patterns for
/// select operations.
enum SelectPatternFlavor {
SPF_UNKNOWN = 0,
SPF_SMIN, SPF_UMIN,
SPF_SMAX, SPF_UMAX
//SPF_ABS - TODO.
};
namespace {
/// InstCombineWorklist - This is the worklist management logic for
/// InstCombine.
@ -281,6 +290,9 @@ namespace {
Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI,
Instruction *FI);
Instruction *FoldSelectIntoOp(SelectInst &SI, Value*, Value*);
Instruction *FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1,
Value *A, Value *B, Instruction &Outer,
SelectPatternFlavor SPF2, Value *C);
Instruction *visitSelectInst(SelectInst &SI);
Instruction *visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
Instruction *visitCallInst(CallInst &CI);
@ -649,6 +661,57 @@ static inline Value *dyn_castFNegVal(Value *V) {
return 0;
}
/// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms,
/// returning the kind and providing the out parameter results if we
/// successfully match.
static SelectPatternFlavor
MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) {
SelectInst *SI = dyn_cast<SelectInst>(V);
if (SI == 0) return SPF_UNKNOWN;
ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition());
if (ICI == 0) return SPF_UNKNOWN;
LHS = ICI->getOperand(0);
RHS = ICI->getOperand(1);
// (icmp X, Y) ? X : Y
if (SI->getTrueValue() == ICI->getOperand(0) &&
SI->getFalseValue() == ICI->getOperand(1)) {
switch (ICI->getPredicate()) {
default: return SPF_UNKNOWN; // Equality.
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE: return SPF_UMAX;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: return SPF_SMAX;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE: return SPF_UMIN;
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: return SPF_SMIN;
}
}
// (icmp X, Y) ? Y : X
if (SI->getTrueValue() == ICI->getOperand(1) &&
SI->getFalseValue() == ICI->getOperand(0)) {
switch (ICI->getPredicate()) {
default: return SPF_UNKNOWN; // Equality.
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE: return SPF_UMIN;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: return SPF_SMIN;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE: return SPF_UMAX;
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: return SPF_SMAX;
}
}
// TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5)
return SPF_UNKNOWN;
}
/// isFreeToInvert - Return true if the specified value is free to invert (apply
/// ~ to). This happens in cases where the ~ can be eliminated.
static inline bool isFreeToInvert(Value *V) {
@ -733,12 +796,12 @@ static bool MultiplyOverflows(ConstantInt *C1, ConstantInt *C2, bool sign) {
APInt MulExt = LHSExt * RHSExt;
if (sign) {
APInt Min = APInt::getSignedMinValue(W).sext(W * 2);
APInt Max = APInt::getSignedMaxValue(W).sext(W * 2);
return MulExt.slt(Min) || MulExt.sgt(Max);
} else
if (!sign)
return MulExt.ugt(APInt::getLowBitsSet(W * 2, W));
APInt Min = APInt::getSignedMinValue(W).sext(W * 2);
APInt Max = APInt::getSignedMaxValue(W).sext(W * 2);
return MulExt.slt(Min) || MulExt.sgt(Max);
}
@ -9479,9 +9542,6 @@ Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
return ReplaceInstUsesWith(SI, TrueVal);
/// NOTE: if we wanted to, this is where to detect integer MIN/MAX
}
/// NOTE: if we wanted to, this is where to detect integer ABS
return Changed ? &SI : 0;
}
@ -9523,6 +9583,35 @@ static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V,
return false;
}
/// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form:
/// SPF2(SPF1(A, B), C)
Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner,
SelectPatternFlavor SPF1,
Value *A, Value *B,
Instruction &Outer,
SelectPatternFlavor SPF2, Value *C) {
if (C == A || C == B) {
// MAX(MAX(A, B), B) -> MAX(A, B)
// MIN(MIN(a, b), a) -> MIN(a, b)
if (SPF1 == SPF2)
return ReplaceInstUsesWith(Outer, Inner);
// MAX(MIN(a, b), a) -> a
// MIN(MAX(a, b), a) -> a
if (SPF1 == SPF_SMIN && SPF2 == SPF_SMAX ||
SPF1 == SPF_SMAX && SPF2 == SPF_SMIN ||
SPF1 == SPF_UMIN && SPF2 == SPF_UMAX ||
SPF1 == SPF_UMAX && SPF2 == SPF_UMIN)
return ReplaceInstUsesWith(Outer, C);
}
// TODO: MIN(MIN(A, 23), 97)
return 0;
}
Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
Value *CondVal = SI.getCondition();
Value *TrueVal = SI.getTrueValue();
@ -9729,9 +9818,28 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
// See if we can fold the select into one of our operands.
if (SI.getType()->isInteger()) {
Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal);
if (FoldI)
if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
return FoldI;
// MAX(MAX(a, b), a) -> MAX(a, b)
// MIN(MIN(a, b), a) -> MIN(a, b)
// MAX(MIN(a, b), a) -> a
// MIN(MAX(a, b), a) -> a
Value *LHS, *RHS, *LHS2, *RHS2;
if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) {
if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
SI, SPF, RHS))
return R;
if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2))
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
SI, SPF, LHS))
return R;
}
// TODO.
// ABS(-X) -> ABS(X)
// ABS(ABS(X)) -> ABS(X)
}
// See if we can fold the select into a phi node if the condition is a select.

40
test/Transforms/InstCombine/select.ll
View File

@ -382,3 +382,43 @@ next:
; CHECK-NEXT: ret i32 %a
}
define i32 @test30(i32 %x, i32 %y) {
%cmp = icmp sgt i32 %x, %y
%cond = select i1 %cmp, i32 %x, i32 %y
%cmp5 = icmp sgt i32 %cond, %x
%retval = select i1 %cmp5, i32 %cond, i32 %x
ret i32 %retval
}
define i32 @test31(i32 %x, i32 %y) {
%cmp = icmp ugt i32 %x, %y
%cond = select i1 %cmp, i32 %x, i32 %y
%cmp5 = icmp ugt i32 %cond, %x
%retval = select i1 %cmp5, i32 %cond, i32 %x
ret i32 %retval
}
define i32 @test32(i32 %x, i32 %y) {
%cmp = icmp sgt i32 %x, %y
%cond = select i1 %cmp, i32 %y, i32 %x
%cmp5 = icmp sgt i32 %cond, %x
%retval = select i1 %cmp5, i32 %x, i32 %cond
ret i32 %retval
}
define i32 @test33(i32 %x, i32 %y) {
%cmp = icmp sgt i32 %x, %y
%cond = select i1 %cmp, i32 %y, i32 %x
%cmp5 = icmp sgt i32 %cond, %x
%retval = select i1 %cmp5, i32 %cond, i32 %x
ret i32 %retval
}
define i32 @test34(i32 %x, i32 %y) {
%cmp = icmp sgt i32 %x, %y
%cond = select i1 %cmp, i32 %x, i32 %y
%cmp5 = icmp sgt i32 %cond, %x
%retval = select i1 %cmp5, i32 %x, i32 %cond
ret i32 %retval
}