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ScalarEvolution support for <= and >= loops.

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Also, generalize ScalarEvolutions's min and max recognition to handle
some new forms of min and max that this change makes more common.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@102234 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-04-24 03:09:42 +00:00
parent d19bba69ad
commit 9f93d30a26
5 changed files with 138 additions and 24 deletions
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127
lib/Analysis/ScalarEvolution.cpp
View File

@ -3416,10 +3416,22 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
// fall through
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE:
if (LHS == U->getOperand(1) && RHS == U->getOperand(2))
return getSMaxExpr(getSCEV(LHS), getSCEV(RHS));
else if (LHS == U->getOperand(2) && RHS == U->getOperand(1))
return getSMinExpr(getSCEV(LHS), getSCEV(RHS));
// a >s b ? a+x : b+x -> smax(a, b)+x
// a >s b ? b+x : a+x -> smin(a, b)+x
if (LHS->getType() == U->getType()) {
const SCEV *LS = getSCEV(LHS);
const SCEV *RS = getSCEV(RHS);
const SCEV *LA = getSCEV(U->getOperand(1));
const SCEV *RA = getSCEV(U->getOperand(2));
const SCEV *LDiff = getMinusSCEV(LA, LS);
const SCEV *RDiff = getMinusSCEV(RA, RS);
if (LDiff == RDiff)
return getAddExpr(getSMaxExpr(LS, RS), LDiff);
LDiff = getMinusSCEV(LA, RS);
RDiff = getMinusSCEV(RA, LS);
if (LDiff == RDiff)
return getAddExpr(getSMinExpr(LS, RS), LDiff);
}
break;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE:
@ -3427,28 +3439,52 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
// fall through
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE:
if (LHS == U->getOperand(1) && RHS == U->getOperand(2))
return getUMaxExpr(getSCEV(LHS), getSCEV(RHS));
else if (LHS == U->getOperand(2) && RHS == U->getOperand(1))
return getUMinExpr(getSCEV(LHS), getSCEV(RHS));
// a >u b ? a+x : b+x -> umax(a, b)+x
// a >u b ? b+x : a+x -> umin(a, b)+x
if (LHS->getType() == U->getType()) {
const SCEV *LS = getSCEV(LHS);
const SCEV *RS = getSCEV(RHS);
const SCEV *LA = getSCEV(U->getOperand(1));
const SCEV *RA = getSCEV(U->getOperand(2));
const SCEV *LDiff = getMinusSCEV(LA, LS);
const SCEV *RDiff = getMinusSCEV(RA, RS);
if (LDiff == RDiff)
return getAddExpr(getUMaxExpr(LS, RS), LDiff);
LDiff = getMinusSCEV(LA, RS);
RDiff = getMinusSCEV(RA, LS);
if (LDiff == RDiff)
return getAddExpr(getUMinExpr(LS, RS), LDiff);
}
break;
case ICmpInst::ICMP_NE:
// n != 0 ? n : 1 -> umax(n, 1)
if (LHS == U->getOperand(1) &&
isa<ConstantInt>(U->getOperand(2)) &&
cast<ConstantInt>(U->getOperand(2))->isOne() &&
// n != 0 ? n+x : 1+x -> umax(n, 1)+x
if (LHS->getType() == U->getType() &&
isa<ConstantInt>(RHS) &&
cast<ConstantInt>(RHS)->isZero())
return getUMaxExpr(getSCEV(LHS), getSCEV(U->getOperand(2)));
cast<ConstantInt>(RHS)->isZero()) {
const SCEV *One = getConstant(LHS->getType(), 1);
const SCEV *LS = getSCEV(LHS);
const SCEV *LA = getSCEV(U->getOperand(1));
const SCEV *RA = getSCEV(U->getOperand(2));
const SCEV *LDiff = getMinusSCEV(LA, LS);
const SCEV *RDiff = getMinusSCEV(RA, One);
if (LDiff == RDiff)
return getAddExpr(getUMaxExpr(LS, One), LDiff);
}
break;
case ICmpInst::ICMP_EQ:
// n == 0 ? 1 : n -> umax(n, 1)
if (LHS == U->getOperand(2) &&
isa<ConstantInt>(U->getOperand(1)) &&
cast<ConstantInt>(U->getOperand(1))->isOne() &&
// n == 0 ? 1+x : n+x -> umax(n, 1)+x
if (LHS->getType() == U->getType() &&
isa<ConstantInt>(RHS) &&
cast<ConstantInt>(RHS)->isZero())
return getUMaxExpr(getSCEV(LHS), getSCEV(U->getOperand(1)));
cast<ConstantInt>(RHS)->isZero()) {
const SCEV *One = getConstant(LHS->getType(), 1);
const SCEV *LS = getSCEV(LHS);
const SCEV *LA = getSCEV(U->getOperand(1));
const SCEV *RA = getSCEV(U->getOperand(2));
const SCEV *LDiff = getMinusSCEV(LA, One);
const SCEV *RDiff = getMinusSCEV(RA, LS);
if (LDiff == RDiff)
return getAddExpr(getUMaxExpr(LS, One), LDiff);
}
break;
default:
break;
@ -3885,6 +3921,57 @@ ScalarEvolution::ComputeBackedgeTakenCountFromExitCondICmp(const Loop *L,
if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
}
// If possible, canonicalize GE/LE comparisons to GT/LT comparisons, by
// adding or subtracting 1 from one of the operands.
switch (Cond) {
case ICmpInst::ICMP_SLE:
if (!getSignedRange(RHS).getSignedMax().isMaxSignedValue()) {
RHS = getAddExpr(getConstant(RHS->getType(), 1, true), RHS,
/*HasNUW=*/false, /*HasNSW=*/true);
Cond = ICmpInst::ICMP_SLT;
} else if (!getSignedRange(LHS).getSignedMin().isMinSignedValue()) {
LHS = getAddExpr(getConstant(RHS->getType(), -1, true), LHS,
/*HasNUW=*/false, /*HasNSW=*/true);
Cond = ICmpInst::ICMP_SLT;
}
break;
case ICmpInst::ICMP_SGE:
if (!getSignedRange(RHS).getSignedMin().isMinSignedValue()) {
RHS = getAddExpr(getConstant(RHS->getType(), -1, true), RHS,
/*HasNUW=*/false, /*HasNSW=*/true);
Cond = ICmpInst::ICMP_SGT;
} else if (!getSignedRange(LHS).getSignedMax().isMaxSignedValue()) {
LHS = getAddExpr(getConstant(RHS->getType(), 1, true), LHS,
/*HasNUW=*/false, /*HasNSW=*/true);
Cond = ICmpInst::ICMP_SGT;
}
break;
case ICmpInst::ICMP_ULE:
if (!getUnsignedRange(RHS).getUnsignedMax().isMaxValue()) {
RHS = getAddExpr(getConstant(RHS->getType(), 1, false), RHS,
/*HasNUW=*/true, /*HasNSW=*/false);
Cond = ICmpInst::ICMP_ULT;
} else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
LHS = getAddExpr(getConstant(RHS->getType(), -1, false), LHS,
/*HasNUW=*/true, /*HasNSW=*/false);
Cond = ICmpInst::ICMP_ULT;
}
break;
case ICmpInst::ICMP_UGE:
if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
RHS = getAddExpr(getConstant(RHS->getType(), -1, false), RHS,
/*HasNUW=*/true, /*HasNSW=*/false);
Cond = ICmpInst::ICMP_UGT;
} else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {
LHS = getAddExpr(getConstant(RHS->getType(), 1, false), LHS,
/*HasNUW=*/true, /*HasNSW=*/false);
Cond = ICmpInst::ICMP_UGT;
}
break;
default:
break;
}
switch (Cond) {
case ICmpInst::ICMP_NE: { // while (X != Y)
// Convert to: while (X-Y != 0)

1
test/Analysis/ScalarEvolution/2008-11-18-LessThanOrEqual.ll
View File

@ -1,6 +1,5 @@
; RUN: opt < %s -analyze -scalar-evolution |& \
; RUN: grep {Loop %bb: backedge-taken count is (7 + (-1 \\* %argc))}
; XFAIL: *
define i32 @main(i32 %argc, i8** %argv) nounwind {
entry:

1
test/Analysis/ScalarEvolution/2008-12-08-FiniteSGE.ll
View File

@ -1,5 +1,4 @@
; RUN: opt < %s -analyze -scalar-evolution | grep {backedge-taken count is 255}
; XFAIL: *
define i32 @foo(i32 %x, i32 %y, i32* %lam, i32* %alp) nounwind {
bb1.thread:

6
test/Analysis/ScalarEvolution/2008-12-11-SMaxOverflow.ll
View File

@ -1,5 +1,7 @@
; RUN: opt < %s -analyze -scalar-evolution | grep {0 smax}
; XFAIL: *
; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
; CHECK: @f
; CHECK: Loop %bb16.preheader: backedge-taken count is (-1 + %c.idx.val)
define i32 @f(i32 %c.idx.val) {

27
test/Analysis/ScalarEvolution/sle.ll Normal file
View File

@ -0,0 +1,27 @@
; RUN: opt -analyze -scalar-evolution < %s | FileCheck %s
; ScalarEvolution should be able to use nsw information to prove that
; this loop has a finite trip count.
; CHECK: @le
; CHECK: Loop %for.body: backedge-taken count is %n
; CHECK: Loop %for.body: max backedge-taken count is 9223372036854775807
define void @le(i64 %n, double* nocapture %p) nounwind {
entry:
%cmp6 = icmp slt i64 %n, 0 ; <i1> [#uses=1]
br i1 %cmp6, label %for.end, label %for.body
for.body: ; preds = %for.body, %entry
%i = phi i64 [ %i.next, %for.body ], [ 0, %entry ] ; <i64> [#uses=2]
%arrayidx = getelementptr double* %p, i64 %i ; <double*> [#uses=2]
%t4 = load double* %arrayidx ; <double> [#uses=1]
%mul = fmul double %t4, 2.200000e+00 ; <double> [#uses=1]
store double %mul, double* %arrayidx
%i.next = add nsw i64 %i, 1 ; <i64> [#uses=2]
%cmp = icmp sgt i64 %i.next, %n ; <i1> [#uses=1]
br i1 %cmp, label %for.end, label %for.body
for.end: ; preds = %for.body, %entry
ret void
}