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LoopIdiom: Add checks to avoid turning memmove into an infinite loop. 

I don't think this is possible with the current implementation but that may change eventually.

llvm-svn: 166877
This commit is contained in:
Benjamin Kramer 2012-10-27 15:18:28 +00:00
parent 2ea126e73e
commit 8d2ee55a0c
2 changed files with 54 additions and 3 deletions
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4
llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
View File

@ -178,7 +178,7 @@ bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) {
// Disable loop idiom recognition if the function's name is a common idiom.
StringRef Name = L->getHeader()->getParent()->getName();
if (Name == "memset" || Name == "memcpy")
if (Name == "memset" || Name == "memcpy" || Name == "memmove")
return false;
// The trip count of the loop must be analyzable.
@ -524,7 +524,7 @@ processLoopStoreOfLoopLoad(StoreInst *SI, unsigned StoreSize,
const SCEVAddRecExpr *LoadEv,
const SCEV *BECount) {
// If we're not allowed to form memcpy, we fail.
if (!TLI->has(LibFunc::memcpy))
if (!TLI->has(LibFunc::memcpy) || !TLI->has(LibFunc::memmove))
return false;
LoadInst *LI = cast<LoadInst>(SI->getValueOperand());

53
llvm/test/Transforms/LoopIdiom/memset_noidiom.ll
View File

@ -1,4 +1,4 @@
; RUN: opt -loop-idiom < %s -S | FileCheck %s
; RUN: opt -basicaa -loop-idiom < %s -S | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin10.0.0"
@ -28,3 +28,54 @@ for.end: ; preds = %for.cond.for.end_cr
ret i8* %b
}
; CHECK: @memcpy
; CHECK-NOT: llvm.memcpy
define i8* @memcpy(i8* noalias %dst, i8* noalias %src, i64 %n) nounwind {
entry:
%tobool3 = icmp eq i64 %n, 0
br i1 %tobool3, label %while.end, label %while.body
while.body: ; preds = %entry, %while.body
%c2.06 = phi i8* [ %incdec.ptr, %while.body ], [ %src, %entry ]
%c1.05 = phi i8* [ %incdec.ptr1, %while.body ], [ %dst, %entry ]
%n.addr.04 = phi i64 [ %dec, %while.body ], [ %n, %entry ]
%dec = add i64 %n.addr.04, -1
%incdec.ptr = getelementptr inbounds i8* %c2.06, i64 1
%0 = load i8* %c2.06, align 1
%incdec.ptr1 = getelementptr inbounds i8* %c1.05, i64 1
store i8 %0, i8* %c1.05, align 1
%tobool = icmp eq i64 %dec, 0
br i1 %tobool, label %while.end, label %while.body
while.end: ; preds = %while.body, %entry
ret i8* %dst
}
; CHECK: @memmove
; CHECK-NOT: llvm.memmove
define i8* @memmove(i8* %dst, i8* nocapture %src, i64 %count) nounwind {
entry:
%sub = add i64 %count, -1
%tobool9 = icmp eq i64 %count, 0
br i1 %tobool9, label %while.end, label %while.body.lr.ph
while.body.lr.ph: ; preds = %entry
%add.ptr2 = getelementptr inbounds i8* %src, i64 %sub
%add.ptr = getelementptr inbounds i8* %dst, i64 %sub
br label %while.body
while.body: ; preds = %while.body.lr.ph, %while.body
%b.012 = phi i8* [ %add.ptr2, %while.body.lr.ph ], [ %incdec.ptr, %while.body ]
%a.011 = phi i8* [ %add.ptr, %while.body.lr.ph ], [ %incdec.ptr3, %while.body ]
%count.addr.010 = phi i64 [ %count, %while.body.lr.ph ], [ %dec, %while.body ]
%dec = add i64 %count.addr.010, -1
%incdec.ptr = getelementptr inbounds i8* %b.012, i64 -1
%0 = load i8* %b.012, align 1
%incdec.ptr3 = getelementptr inbounds i8* %a.011, i64 -1
store i8 %0, i8* %a.011, align 1
%tobool = icmp eq i64 %dec, 0
br i1 %tobool, label %while.end, label %while.body
while.end: ; preds = %while.body, %entry
ret i8* %dst
}