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ScalarEvolution: do not set nuw when creating exprs of form <expr> + <all-ones>.

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The nuw constraint will not be satisfied unless <expr> == 0.

This bug has been around since r102234 (in 2010!), but was uncovered by
r251052, which introduced more aggressive optimization of nuw scev expressions.

Differential Revision: http://reviews.llvm.org/D14850

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253627 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne 2015-11-20 01:26:13 +00:00
parent 77072b3170
commit 5178bc957a
2 changed files with 51 additions and 4 deletions
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6
lib/Analysis/ScalarEvolution.cpp
View File

@ -7045,16 +7045,14 @@ bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
Pred = ICmpInst::ICMP_ULT; Pred = ICmpInst::ICMP_ULT;
Changed = true; Changed = true;
} else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) { } else if (!getUnsignedRange(LHS).getUnsignedMin().isMinValue()) {
LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS, LHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), LHS);
SCEV::FlagNUW);
Pred = ICmpInst::ICMP_ULT; Pred = ICmpInst::ICMP_ULT;
Changed = true; Changed = true;
} }
break; break;
case ICmpInst::ICMP_UGE: case ICmpInst::ICMP_UGE:
if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) { if (!getUnsignedRange(RHS).getUnsignedMin().isMinValue()) {
RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS, RHS = getAddExpr(getConstant(RHS->getType(), (uint64_t)-1, true), RHS);
SCEV::FlagNUW);
Pred = ICmpInst::ICMP_UGT; Pred = ICmpInst::ICMP_UGT;
Changed = true; Changed = true;
} else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) { } else if (!getUnsignedRange(LHS).getUnsignedMax().isMaxValue()) {

49
test/Transforms/IndVarSimplify/zext-nuw.ll Normal file
View File

@ -0,0 +1,49 @@
; RUN: opt -indvars -S %s | FileCheck %s
%struct.A = type { i8 }
@c = global %struct.A* null
@d = global i32 4
define void @_Z3fn1v() {
%x2 = load i32, i32* @d
%x3 = icmp slt i32 %x2, 1
%x4 = select i1 %x3, i32 1, i32 %x2
%x5 = load %struct.A*, %struct.A** @c
%j.sroa.0.0..sroa_idx = getelementptr %struct.A, %struct.A* %x5, i64 0, i32 0
%j.sroa.0.0.copyload = load i8, i8* %j.sroa.0.0..sroa_idx
br label %.preheader4.lr.ph
.preheader4.lr.ph: ; preds = %0
; CHECK-NOT: add i64 {{.*}}, 4294967296
br label %.preheader4
.preheader4: ; preds = %x22, %.preheader4.lr.ph
%k.09 = phi i8* [ undef, %.preheader4.lr.ph ], [ %x25, %x22 ]
%x8 = icmp ult i32 0, 4
br i1 %x8, label %.preheader.lr.ph, label %x22
.preheader.lr.ph: ; preds = %.preheader4
br label %.preheader
.preheader: ; preds = %x17, %.preheader.lr.ph
%k.17 = phi i8* [ %k.09, %.preheader.lr.ph ], [ %x19, %x17 ]
%v.06 = phi i32 [ 0, %.preheader.lr.ph ], [ %x20, %x17 ]
br label %x17
x17: ; preds = %.preheader
%x18 = sext i8 %j.sroa.0.0.copyload to i64
%x19 = getelementptr i8, i8* %k.17, i64 %x18
%x20 = add i32 %v.06, 1
%x21 = icmp ult i32 %x20, %x4
br i1 %x21, label %.preheader, label %._crit_edge.8
._crit_edge.8: ; preds = %x17
%split = phi i8* [ %x19, %x17 ]
br label %x22
x22: ; preds = %._crit_edge.8, %.preheader4
%k.1.lcssa = phi i8* [ %split, %._crit_edge.8 ], [ %k.09, %.preheader4 ]
%x25 = getelementptr i8, i8* %k.1.lcssa
br label %.preheader4
}