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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166877 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 54 insertions, 3 deletions

diff --git a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
index 495d403..bc8ae66 100644
--- a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -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());
diff --git a/test/Transforms/LoopIdiom/memset_noidiom.ll b/test/Transforms/LoopIdiom/memset_noidiom.ll
index 168eb95..27ef4f6 100644
--- a/test/Transforms/LoopIdiom/memset_noidiom.ll
+++ b/test/Transforms/LoopIdiom/memset_noidiom.ll
@@ -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
+}