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Fill in some holes in ScalarEvolution's loop iteration condition

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analysis. This allows indvars to emit a simpler loop trip count
expression.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76085 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-07-16 17:34:36 +00:00
parent 358ab1dbb0
commit 850f791abc
2 changed files with 65 additions and 2 deletions
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29
lib/Analysis/ScalarEvolution.cpp
View File

@ -960,6 +960,22 @@ const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
return getAddRecExpr(getSignExtendExpr(Start, Ty),
getSignExtendExpr(Step, Ty),
L);
// Similar to above, only this time treat the step value as unsigned.
// This covers loops that count up with an unsigned step.
const SCEV *UMul =
getMulExpr(CastedMaxBECount,
getTruncateOrZeroExtend(Step, Start->getType()));
Add = getAddExpr(Start, UMul);
OperandExtendedAdd =
getAddExpr(getZeroExtendExpr(Start, WideTy),
getMulExpr(getZeroExtendExpr(CastedMaxBECount, WideTy),
getZeroExtendExpr(Step, WideTy)));
if (getZeroExtendExpr(Add, WideTy) == OperandExtendedAdd)
// Return the expression with the addrec on the outside.
return getAddRecExpr(getSignExtendExpr(Start, Ty),
getZeroExtendExpr(Step, Ty),
L);
}
// If the backedge is guarded by a comparison with the pre-inc value
@ -4248,7 +4264,7 @@ bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,
switch (Pred) {
default:
assert(0 && "Unexpected ICmpInst::Predicate value!");
llvm_unreachable("Unexpected ICmpInst::Predicate value!");
break;
case ICmpInst::ICMP_SGT:
Pred = ICmpInst::ICMP_SLT;
@ -4556,23 +4572,32 @@ ScalarEvolution::isNecessaryCondOperands(ICmpInst::Predicate Pred,
const SCEV *FoundLHS,
const SCEV *FoundRHS) {
switch (Pred) {
default: break;
default: llvm_unreachable("Unexpected ICmpInst::Predicate value!");
case ICmpInst::ICMP_EQ:
case ICmpInst::ICMP_NE:
if (HasSameValue(LHS, FoundLHS) && HasSameValue(RHS, FoundRHS))
return true;
break;
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE:
if (isKnownPredicate(ICmpInst::ICMP_SLE, LHS, FoundLHS) &&
isKnownPredicate(ICmpInst::ICMP_SGE, RHS, FoundRHS))
return true;
break;
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE:
if (isKnownPredicate(ICmpInst::ICMP_SGE, LHS, FoundLHS) &&
isKnownPredicate(ICmpInst::ICMP_SLE, RHS, FoundRHS))
return true;
break;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE:
if (isKnownPredicate(ICmpInst::ICMP_ULE, LHS, FoundLHS) &&
isKnownPredicate(ICmpInst::ICMP_UGE, RHS, FoundRHS))
return true;
break;
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE:
if (isKnownPredicate(ICmpInst::ICMP_UGE, LHS, FoundLHS) &&
isKnownPredicate(ICmpInst::ICMP_ULE, RHS, FoundRHS))
return true;

38
test/Transforms/IndVarSimplify/lftr-promote.ll Normal file
View File

@ -0,0 +1,38 @@
; RUN: llvm-as < %s | opt -indvars | llvm-dis | grep add | count 1
; Indvars should be able to compute the exit value of this loop
; without any additional arithmetic. The only add needed should
; be the canonical IV increment.
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
define void @foo(double* %p, i32 %n) nounwind {
entry:
%0 = icmp sgt i32 %n, 0 ; <i1> [#uses=1]
br i1 %0, label %bb.nph, label %return
bb.nph: ; preds = %entry
br label %bb2
bb2: ; preds = %bb3, %bb.nph
%i.01 = phi i32 [ %7, %bb3 ], [ 0, %bb.nph ] ; <i32> [#uses=3]
%1 = sext i32 %i.01 to i64 ; <i64> [#uses=1]
%2 = getelementptr double* %p, i64 %1 ; <double*> [#uses=1]
%3 = load double* %2, align 8 ; <double> [#uses=1]
%4 = fmul double %3, 1.100000e+00 ; <double> [#uses=1]
%5 = sext i32 %i.01 to i64 ; <i64> [#uses=1]
%6 = getelementptr double* %p, i64 %5 ; <double*> [#uses=1]
store double %4, double* %6, align 8
%7 = add i32 %i.01, 1 ; <i32> [#uses=2]
br label %bb3
bb3: ; preds = %bb2
%8 = icmp slt i32 %7, %n ; <i1> [#uses=1]
br i1 %8, label %bb2, label %bb3.return_crit_edge
bb3.return_crit_edge: ; preds = %bb3
br label %return
return: ; preds = %bb3.return_crit_edge, %entry
ret void
}