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LoopVectorize: Math functions only read rounding mode

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Math functions are mark as readonly because they read the floating point
rounding mode. Because we don't vectorize loops that would contain function
calls that set the rounding mode it is safe to ignore this memory read.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185299 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnold Schwaighofer
2013-07-01 00:54:44 +00:00
parent c36a8d2b3d
commit c14380d195
2 changed files with 39 additions and 0 deletions
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7
lib/Transforms/Vectorize/LoopVectorize.cpp
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@ -3520,6 +3520,13 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
// but is not a load, then we quit. Notice that we don't handle function
// calls that read or write.
if (it->mayReadFromMemory()) {
// Many math library functions read the rounding mode. We will only
// vectorize a loop if it contains known function calls that don't set
// the flag. Therefore, it is safe to ignore this read from memory.
CallInst *Call = dyn_cast<CallInst>(it);
if (Call && getIntrinsicIDForCall(Call, TLI))
continue;
LoadInst *Ld = dyn_cast<LoadInst>(it);
if (!Ld) return false;
if (!Ld->isSimple() && !IsAnnotatedParallel) {