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[SCEV] Add transform zext((A * B * ...)<nuw>) --> (zext(A) * zext(B) * ...)<nuw>. 

Reviewers: sanjoy

Subscribers: hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D48041

llvm-svn: 334429
This commit is contained in:
Justin Lebar 2018-06-11 18:57:58 +00:00
parent aa4fec94d8
commit 4da41c13a5
2 changed files with 43 additions and 0 deletions
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12
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -1778,6 +1778,18 @@ ScalarEvolution::getZeroExtendExpr(const SCEV *Op, Type *Ty, unsigned Depth) {
}
}
if (auto *SA = dyn_cast<SCEVMulExpr>(Op)) {
// zext((A * B * ...)<nuw>) --> (zext(A) * zext(B) * ...)<nuw>
if (SA->hasNoUnsignedWrap()) {
// If the multiply does not unsign overflow then we can, by definition,
// commute the zero extension with the multiply operation.
SmallVector<const SCEV *, 4> Ops;
for (const auto *Op : SA->operands())
Ops.push_back(getZeroExtendExpr(Op, Ty, Depth + 1));
return getMulExpr(Ops, SCEV::FlagNUW, Depth + 1);
}
}
// 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;

31
llvm/test/Analysis/ScalarEvolution/zext-mul.ll Normal file
View File

@ -0,0 +1,31 @@
; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
; Check that we convert
; zext((a * b)<nuw>)
; to
; (zext(a) * zext(b))<nuw>
declare i32 @get_int();
; Transform doesn't apply here, because %a lacks range metadata.
; CHECK-LABEL: @no_range
define void @no_range() {
%a = call i32 @get_int()
%b = mul i32 %a, 4
%c = zext i32 %b to i64
; CHECK: %c
; CHECK-NEXT: --> (zext i32 (4 * %a) to i64)
ret void
}
; CHECK-LABEL: @range
define void @range() {
%a = call i32 @get_int(), !range !0
%b = mul i32 %a, 4
%c = zext i32 %b to i64
; CHECK: %c
; CHECK-NEXT: --> (4 * (zext i32 %a to i64))<nuw>
ret void
}
!0 = !{i32 0, i32 100}