<div dir="ltr">Why does <span style="font-size:12.8px">(add (zext x), cst) --> (zext (add x, cst')) check for signed overflow but then create an NUW add. That's not valid is it?</span></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature">~Craig</div></div>
<br><div class="gmail_quote">On Thu, Dec 29, 2016 at 4:28 PM, David Majnemer via llvm-commits <span dir="ltr"><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: majnemer<br>
Date: Thu Dec 29 18:28:58 2016<br>
New Revision: 290733<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=290733&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project?rev=290733&view=rev</a><br>
Log:<br>
[InstCombine] More thoroughly canonicalize the position of zexts<br>
<br>
We correctly canonicalized (add (sext x), (sext y)) to (sext (add x, y))<br>
where possible. However, we didn't perform the same canonicalization<br>
for zexts or for muls.<br>
<br>
Modified:<br>
llvm/trunk/lib/Transforms/<wbr>InstCombine/InstCombineAddSub.<wbr>cpp<br>
llvm/trunk/lib/Transforms/<wbr>InstCombine/<wbr>InstCombineMulDivRem.cpp<br>
<br>
Modified: llvm/trunk/lib/Transforms/<wbr>InstCombine/InstCombineAddSub.<wbr>cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp?rev=290733&r1=290732&r2=290733&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/llvm/trunk/lib/<wbr>Transforms/InstCombine/<wbr>InstCombineAddSub.cpp?rev=<wbr>290733&r1=290732&r2=290733&<wbr>view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/lib/Transforms/<wbr>InstCombine/InstCombineAddSub.<wbr>cpp (original)<br>
+++ llvm/trunk/lib/Transforms/<wbr>InstCombine/InstCombineAddSub.<wbr>cpp Thu Dec 29 18:28:58 2016<br>
@@ -1226,15 +1226,16 @@ Instruction *InstCombiner::visitAdd(Bina<br>
if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) {<br>
// (add (sext x), cst) --> (sext (add x, cst'))<br>
if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {<br>
- Constant *CI =<br>
- ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)-><wbr>getType());<br>
- if (LHSConv->hasOneUse() &&<br>
- ConstantExpr::getSExt(CI, I.getType()) == RHSC &&<br>
- WillNotOverflowSignedAdd(<wbr>LHSConv->getOperand(0), CI, I)) {<br>
- // Insert the new, smaller add.<br>
- Value *NewAdd = Builder->CreateNSWAdd(LHSConv-<wbr>>getOperand(0),<br>
- CI, "addconv");<br>
- return new SExtInst(NewAdd, I.getType());<br>
+ if (LHSConv->hasOneUse()) {<br>
+ Constant *CI =<br>
+ ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)-><wbr>getType());<br>
+ if (ConstantExpr::getSExt(CI, I.getType()) == RHSC &&<br>
+ WillNotOverflowSignedAdd(<wbr>LHSConv->getOperand(0), CI, I)) {<br>
+ // Insert the new, smaller add.<br>
+ Value *NewAdd =<br>
+ Builder->CreateNSWAdd(LHSConv-<wbr>>getOperand(0), CI, "addconv");<br>
+ return new SExtInst(NewAdd, I.getType());<br>
+ }<br>
}<br>
}<br>
<br>
@@ -1255,6 +1256,43 @@ Instruction *InstCombiner::visitAdd(Bina<br>
}<br>
}<br>
}<br>
+<br>
+ // Check for (add (zext x), y), see if we can merge this into an<br>
+ // integer add followed by a zext.<br>
+ if (auto *LHSConv = dyn_cast<ZExtInst>(LHS)) {<br>
+ // (add (zext x), cst) --> (zext (add x, cst'))<br>
+ if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {<br>
+ if (LHSConv->hasOneUse()) {<br>
+ Constant *CI =<br>
+ ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)-><wbr>getType());<br>
+ if (ConstantExpr::getZExt(CI, I.getType()) == RHSC &&<br>
+ WillNotOverflowSignedAdd(<wbr>LHSConv->getOperand(0), CI, I)) {<br>
+ // Insert the new, smaller add.<br>
+ Value *NewAdd =<br>
+ Builder->CreateNUWAdd(LHSConv-<wbr>>getOperand(0), CI, "addconv");<br>
+ return new ZExtInst(NewAdd, I.getType());<br>
+ }<br>
+ }<br>
+ }<br>
+<br>
+ // (add (zext x), (zext y)) --> (zext (add int x, y))<br>
+ if (auto *RHSConv = dyn_cast<ZExtInst>(RHS)) {<br>
+ // Only do this if x/y have the same type, if at last one of them has a<br>
+ // single use (so we don't increase the number of zexts), and if the<br>
+ // integer add will not overflow.<br>
+ if (LHSConv->getOperand(0)-><wbr>getType() ==<br>
+ RHSConv->getOperand(0)-><wbr>getType() &&<br>
+ (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&<br>
+ computeOverflowForUnsignedAdd(<wbr>LHSConv->getOperand(0),<br>
+ RHSConv->getOperand(0),<br>
+ &I) == OverflowResult::<wbr>NeverOverflows) {<br>
+ // Insert the new integer add.<br>
+ Value *NewAdd = Builder->CreateNUWAdd(<br>
+ LHSConv->getOperand(0), RHSConv->getOperand(0), "addconv");<br>
+ return new ZExtInst(NewAdd, I.getType());<br>
+ }<br>
+ }<br>
+ }<br>
<br>
// (add (xor A, B) (and A, B)) --> (or A, B)<br>
{<br>
<br>
Modified: llvm/trunk/lib/Transforms/<wbr>InstCombine/<wbr>InstCombineMulDivRem.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp?rev=290733&r1=290732&r2=290733&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/llvm/trunk/lib/<wbr>Transforms/InstCombine/<wbr>InstCombineMulDivRem.cpp?rev=<wbr>290733&r1=290732&r2=290733&<wbr>view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/lib/Transforms/<wbr>InstCombine/<wbr>InstCombineMulDivRem.cpp (original)<br>
+++ llvm/trunk/lib/Transforms/<wbr>InstCombine/<wbr>InstCombineMulDivRem.cpp Thu Dec 29 18:28:58 2016<br>
@@ -389,6 +389,79 @@ Instruction *InstCombiner::visitMul(Bina<br>
}<br>
}<br>
<br>
+ // Check for (mul (sext x), y), see if we can merge this into an<br>
+ // integer mul followed by a sext.<br>
+ if (SExtInst *Op0Conv = dyn_cast<SExtInst>(Op0)) {<br>
+ // (mul (sext x), cst) --> (sext (mul x, cst'))<br>
+ if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {<br>
+ if (Op0Conv->hasOneUse()) {<br>
+ Constant *CI =<br>
+ ConstantExpr::getTrunc(Op1C, Op0Conv->getOperand(0)-><wbr>getType());<br>
+ if (ConstantExpr::getSExt(CI, I.getType()) == Op1C &&<br>
+ WillNotOverflowSignedMul(<wbr>Op0Conv->getOperand(0), CI, I)) {<br>
+ // Insert the new, smaller mul.<br>
+ Value *NewMul =<br>
+ Builder->CreateNSWMul(Op0Conv-<wbr>>getOperand(0), CI, "mulconv");<br>
+ return new SExtInst(NewMul, I.getType());<br>
+ }<br>
+ }<br>
+ }<br>
+<br>
+ // (mul (sext x), (sext y)) --> (sext (mul int x, y))<br>
+ if (SExtInst *Op1Conv = dyn_cast<SExtInst>(Op1)) {<br>
+ // Only do this if x/y have the same type, if at last one of them has a<br>
+ // single use (so we don't increase the number of sexts), and if the<br>
+ // integer mul will not overflow.<br>
+ if (Op0Conv->getOperand(0)-><wbr>getType() ==<br>
+ Op1Conv->getOperand(0)-><wbr>getType() &&<br>
+ (Op0Conv->hasOneUse() || Op1Conv->hasOneUse()) &&<br>
+ WillNotOverflowSignedMul(<wbr>Op0Conv->getOperand(0),<br>
+ Op1Conv->getOperand(0), I)) {<br>
+ // Insert the new integer mul.<br>
+ Value *NewMul = Builder->CreateNSWMul(<br>
+ Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");<br>
+ return new SExtInst(NewMul, I.getType());<br>
+ }<br>
+ }<br>
+ }<br>
+<br>
+ // Check for (mul (zext x), y), see if we can merge this into an<br>
+ // integer mul followed by a zext.<br>
+ if (auto *Op0Conv = dyn_cast<ZExtInst>(Op0)) {<br>
+ // (mul (zext x), cst) --> (zext (mul x, cst'))<br>
+ if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {<br>
+ if (Op0Conv->hasOneUse()) {<br>
+ Constant *CI =<br>
+ ConstantExpr::getTrunc(Op1C, Op0Conv->getOperand(0)-><wbr>getType());<br>
+ if (ConstantExpr::getZExt(CI, I.getType()) == Op1C &&<br>
+ WillNotOverflowSignedMul(<wbr>Op0Conv->getOperand(0), CI, I)) {<br>
+ // Insert the new, smaller mul.<br>
+ Value *NewMul =<br>
+ Builder->CreateNUWMul(Op0Conv-<wbr>>getOperand(0), CI, "mulconv");<br>
+ return new ZExtInst(NewMul, I.getType());<br>
+ }<br>
+ }<br>
+ }<br>
+<br>
+ // (mul (zext x), (zext y)) --> (zext (mul int x, y))<br>
+ if (auto *Op1Conv = dyn_cast<ZExtInst>(Op1)) {<br>
+ // Only do this if x/y have the same type, if at last one of them has a<br>
+ // single use (so we don't increase the number of zexts), and if the<br>
+ // integer mul will not overflow.<br>
+ if (Op0Conv->getOperand(0)-><wbr>getType() ==<br>
+ Op1Conv->getOperand(0)-><wbr>getType() &&<br>
+ (Op0Conv->hasOneUse() || Op1Conv->hasOneUse()) &&<br>
+ computeOverflowForUnsignedMul(<wbr>Op0Conv->getOperand(0),<br>
+ Op1Conv->getOperand(0),<br>
+ &I) == OverflowResult::<wbr>NeverOverflows) {<br>
+ // Insert the new integer mul.<br>
+ Value *NewMul = Builder->CreateNUWMul(<br>
+ Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");<br>
+ return new ZExtInst(NewMul, I.getType());<br>
+ }<br>
+ }<br>
+ }<br>
+<br>
if (!I.hasNoSignedWrap() && WillNotOverflowSignedMul(Op0, Op1, I)) {<br>
Changed = true;<br>
I.setHasNoSignedWrap(true);<br>
<br>
<br>
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</blockquote></div><br></div>