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[LSR][SCEVExpander] Avoid blind cast 'Factor' to SCEVConstant in FactorOutConstant. 

Summary:
In SCEVExpander FactorOutConstant(), when GEP indexing into/over scalable vector,
it is legal for the 'Factor' in a MulExpr to be the size of a scalable vector
instead of a compile-time constant.

Current upstream crash with the test attached.

Reviewers: efriedma, sdesmalen, sanjoy.google, mkazantsev

Reviewed By: efriedma

Subscribers: hiraditya, javed.absar, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80973
This commit is contained in:
Huihui Zhang 2020-06-04 10:32:36 -07:00
parent c2625f330f
commit bd43f78c76
2 changed files with 61 additions and 8 deletions
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20
llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
View File

@ -287,14 +287,14 @@ static bool FactorOutConstant(const SCEV *&S, const SCEV *&Remainder,
if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
// Size is known, check if there is a constant operand which is a multiple
// of the given factor. If so, we can factor it.
const SCEVConstant *FC = cast<SCEVConstant>(Factor);
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
if (!C->getAPInt().srem(FC->getAPInt())) {
SmallVector<const SCEV *, 4> NewMulOps(M->op_begin(), M->op_end());
NewMulOps[0] = SE.getConstant(C->getAPInt().sdiv(FC->getAPInt()));
S = SE.getMulExpr(NewMulOps);
return true;
}
if (const SCEVConstant *FC = dyn_cast<SCEVConstant>(Factor))
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
if (!C->getAPInt().srem(FC->getAPInt())) {
SmallVector<const SCEV *, 4> NewMulOps(M->op_begin(), M->op_end());
NewMulOps[0] = SE.getConstant(C->getAPInt().sdiv(FC->getAPInt()));
S = SE.getMulExpr(NewMulOps);
return true;
}
}
// In an AddRec, check if both start and step are divisible.
@ -504,6 +504,10 @@ Value *SCEVExpander::expandAddToGEP(const SCEV *const *op_begin,
if (ArrayType *ATy = dyn_cast<ArrayType>(ElTy))
ElTy = ATy->getElementType();
else
// FIXME: Handle VectorType.
// E.g., If ElTy is scalable vector, then ElSize is not a compile-time
// constant, therefore can not be factored out. The generated IR is less
// ideal with base 'V' cast to i8* and do ugly getelementptr over that.
break;
}

49
llvm/test/Transforms/LoopStrengthReduce/vscale-factor-out-constant.ll Normal file
View File

@ -0,0 +1,49 @@
; RUN: opt -S -loop-reduce < %s | FileCheck %s
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-unknown-linux-gnu"
; This test check SCEVExpander FactorOutConstant() is not crashing with blind cast 'Factor' to SCEVConstant.
; CHECK-LABEL: test
; FIXME: Handle VectorType in SCEVExpander::expandAddToGEP.
; The generated IR is not ideal with base 'scalar_vector' cast to i8*, and do ugly getelementptr over casted base.
; CHECK: uglygep
define void @test(i32* %a, i32 %v, i64 %n) {
entry:
%scalar_vector = alloca <vscale x 4 x i32>, align 16
%num_elm = call i64 @llvm.aarch64.sve.cntw(i32 31)
%scalar_count = and i64 %num_elm, -4
br label %loop_header
exit:
ret void
loop_header:
%indvar = phi i64 [ 0, %entry ], [ %indvar_next, %for_loop ]
%gep_a_0 = getelementptr i32, i32* %a, i64 0
%gep_vec_0 = getelementptr inbounds <vscale x 4 x i32>, <vscale x 4 x i32>* %scalar_vector, i64 0, i64 0
br label %scalar_loop
scalar_loop:
%gep_vec = phi i32* [ %gep_vec_0, %loop_header ], [ %gep_vec_inc, %scalar_loop ]
%scalar_iv = phi i64 [ 0, %loop_header ], [ %scalar_iv_next, %scalar_loop ]
store i32 %v, i32* %gep_vec, align 4
%scalar_iv_next = add i64 %scalar_iv, 1
%gep_vec_inc = getelementptr i32, i32* %gep_vec, i64 1
%scalar_exit = icmp eq i64 %scalar_iv_next, %scalar_count
br i1 %scalar_exit, label %for_loop, label %scalar_loop
for_loop:
%vector = load <vscale x 4 x i32>, <vscale x 4 x i32>* %scalar_vector, align 16
%gep_a = getelementptr i32, i32* %gep_a_0, i64 %indvar
%vector_ptr = bitcast i32* %gep_a to <vscale x 4 x i32>*
call void @llvm.masked.store.nxv4i32.p0nxv4i32(<vscale x 4 x i32> %vector, <vscale x 4 x i32>* %vector_ptr, i32 4, <vscale x 4 x i1> undef)
%indvar_next = add nsw i64 %indvar, %scalar_count
%exit_cond = icmp eq i64 %indvar_next, %n
br i1 %exit_cond, label %exit, label %loop_header
}
declare i64 @llvm.aarch64.sve.cntw(i32 immarg)
declare void @llvm.masked.store.nxv4i32.p0nxv4i32(<vscale x 4 x i32>, <vscale x 4 x i32>*, i32 immarg, <vscale x 4 x i1>)