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[SCEV] Commute zero extends through <nuw> additions

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251052 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das 2015-10-22 19:57:38 +00:00
parent b9d057df5c
commit 63c52aea76
2 changed files with 49 additions and 0 deletions
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12
lib/Analysis/ScalarEvolution.cpp
View File

@ -1559,6 +1559,18 @@ const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
}
}
if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) {
// zext((A + B + ...)<nuw>) --> (zext(A) + zext(B) + ...)<nuw>
if (SA->getNoWrapFlags(SCEV::FlagNUW)) {
// If the addition does not unsign overflow then we can, by definition,
// commute the zero extension with the addition operation.
SmallVector<const SCEV *, 4> Ops;
for (const auto *Op : SA->operands())
Ops.push_back(getZeroExtendExpr(Op, Ty));
return getAddExpr(Ops, SCEV::FlagNUW);
}
}
// The cast wasn't folded; create an explicit cast node.
// Recompute the insert position, as it may have been invalidated.
if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;

37
test/Analysis/ScalarEvolution/no-wrap-add-exprs.ll
View File

@ -83,3 +83,40 @@ define void @f1(i8* %len_addr) {
ret void
}
define void @f2(i8* %len_addr) {
; CHECK-LABEL: Classifying expressions for: @f2
entry:
%len = load i8, i8* %len_addr, !range !0
%len_norange = load i8, i8* %len_addr
; CHECK: %len = load i8, i8* %len_addr, !range !0
; CHECK-NEXT: --> %len U: [0,127) S: [0,127)
; CHECK: %len_norange = load i8, i8* %len_addr
; CHECK-NEXT: --> %len_norange U: full-set S: full-set
%t0 = add i8 %len, 1
%t1 = add i8 %len, 2
; CHECK: %t0 = add i8 %len, 1
; CHECK-NEXT: --> (1 + %len)<nuw><nsw>
; CHECK: %t1 = add i8 %len, 2
; CHECK-NEXT: --> (2 + %len)<nuw>
%t0.zext = zext i8 %t0 to i16
%t1.zext = zext i8 %t1 to i16
; CHECK: %t0.zext = zext i8 %t0 to i16
; CHECK-NEXT: --> (1 + (zext i8 %len to i16))<nuw><nsw> U: [1,128) S: [1,128)
; CHECK: %t1.zext = zext i8 %t1 to i16
; CHECK-NEXT: --> (2 + (zext i8 %len to i16))<nuw><nsw> U: [2,129) S: [2,129)
%q0 = add i8 %len_norange, 1
%q1 = add i8 %len_norange, 2
%q0.zext = zext i8 %q0 to i16
%q1.zext = zext i8 %q1 to i16
; CHECK: %q0.zext = zext i8 %q0 to i16
; CHECK-NEXT: --> (zext i8 (1 + %len_norange) to i16) U: [0,256) S: [0,256)
; CHECK: %q1.zext = zext i8 %q1 to i16
; CHECK-NEXT: --> (zext i8 (2 + %len_norange) to i16) U: [0,256) S: [0,256)
ret void
}