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Teach isDereferenceablePointer() to look through bitcast constant expressions. 

This fixes a LICM regression due to the new load+store pair canonicalization.

Differential Revision: http://reviews.llvm.org/D7411

llvm-svn: 228284
This commit is contained in:
Michael Kuperstein 2015-02-05 09:15:37 +00:00
parent 0857a1da0c
commit d2b6fdbc31
3 changed files with 61 additions and 1 deletions
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14
llvm/include/llvm/IR/Operator.h
View File

@ -504,6 +504,20 @@ public:
}
};
class BitCastOperator
: public ConcreteOperator<Operator, Instruction::BitCast> {
friend class BitCastInst;
friend class ConstantExpr;
public:
Type *getSrcTy() const {
return getOperand(0)->getType();
}
Type *getDestTy() const {
return getType();
}
};
} // End llvm namespace

2
llvm/lib/IR/Value.cpp
View File

@ -496,7 +496,7 @@ static bool isDereferenceablePointer(const Value *V, const DataLayout *DL,
// is at least as large as for the resulting pointer type, then
// we can look through the bitcast.
if (DL)
if (const BitCastInst* BC = dyn_cast<BitCastInst>(V)) {
if (const BitCastOperator *BC = dyn_cast<BitCastOperator>(V)) {
Type *STy = BC->getSrcTy()->getPointerElementType(),
*DTy = BC->getDestTy()->getPointerElementType();
if (STy->isSized() && DTy->isSized() &&

46
llvm/test/Transforms/LICM/constexpr.ll Normal file
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@ -0,0 +1,46 @@
; RUN: opt < %s -S -basicaa -licm | FileCheck %s
; This fixes PR22460
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-windows-msvc"
@in = internal unnamed_addr global i32* null, align 8
@out = internal unnamed_addr global i32* null, align 8
; CHECK-LABEL: @bar
; CHECK: entry:
; CHECK: load i64* bitcast (i32** @in to i64*)
; CHECK: do.body:
; CHECK-NOT: load
define i64 @bar(i32 %N) {
entry:
br label %do.body
do.body: ; preds = %l2, %entry
%i.0 = phi i32 [ 0, %entry ], [ %inc, %l2 ]
%total = phi i64 [ 0, %entry ], [ %next, %l2 ]
%c = icmp eq i32 %N, 6
br i1 %c, label %l1, label %do.body.l2_crit_edge
do.body.l2_crit_edge: ; preds = %do.body
%inval.pre = load i32** @in, align 8
br label %l2
l1: ; preds = %do.body
%v1 = load i64* bitcast (i32** @in to i64*), align 8
store i64 %v1, i64* bitcast (i32** @out to i64*), align 8
%0 = inttoptr i64 %v1 to i32*
br label %l2
l2: ; preds = %do.body.l2_crit_edge, %l1
%inval = phi i32* [ %inval.pre, %do.body.l2_crit_edge ], [ %0, %l1 ]
%int = ptrtoint i32* %inval to i64
%next = add i64 %total, %int
%inc = add nsw i32 %i.0, 1
%cmp = icmp slt i32 %inc, %N
br i1 %cmp, label %do.body, label %do.end
do.end: ; preds = %l2
ret i64 %total
}