<div dir="ltr">Shouldn't this part of canEvaluateTruncated been changed in the original patch to avoid the explosion?<div><br></div><div><div> case Instruction::Add:</div><div> case Instruction::Sub:</div><div> case Instruction::Mul:</div><div> case Instruction::And:</div><div> case Instruction::Or:</div><div> case Instruction::Xor:</div><div> // These operators can all arbitrarily be extended or truncated.</div><div> return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) &&</div><div> canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI);</div></div><div><br></div></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 Mon, Feb 5, 2018 at 1:50 PM, Sanjay Patel 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: spatel<br>
Date: Mon Feb 5 13:50:32 2018<br>
New Revision: 324276<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=324276&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project?rev=324276&view=rev</a><br>
Log:<br>
[InstCombine] don't try to evaluate instructions with >1 use (revert r324014)<br>
<br>
This example causes a compile-time explosion:<br>
<br>
define i16 @foo(i16 %in) {<br>
%x = zext i16 %in to i32<br>
%a1 = mul i32 %x, %x<br>
%a2 = mul i32 %a1, %a1<br>
%a3 = mul i32 %a2, %a2<br>
%a4 = mul i32 %a3, %a3<br>
%a5 = mul i32 %a4, %a4<br>
%a6 = mul i32 %a5, %a5<br>
%a7 = mul i32 %a6, %a6<br>
%a8 = mul i32 %a7, %a7<br>
%a9 = mul i32 %a8, %a8<br>
%a10 = mul i32 %a9, %a9<br>
%a11 = mul i32 %a10, %a10<br>
%a12 = mul i32 %a11, %a11<br>
%a13 = mul i32 %a12, %a12<br>
%a14 = mul i32 %a13, %a13<br>
%a15 = mul i32 %a14, %a14<br>
%a16 = mul i32 %a15, %a15<br>
%a17 = mul i32 %a16, %a16<br>
%a18 = mul i32 %a17, %a17<br>
%a19 = mul i32 %a18, %a18<br>
%a20 = mul i32 %a19, %a19<br>
%a21 = mul i32 %a20, %a20<br>
%a22 = mul i32 %a21, %a21<br>
%a23 = mul i32 %a22, %a22<br>
%a24 = mul i32 %a23, %a23<br>
%T = trunc i32 %a24 to i16<br>
ret i16 %T<br>
}<br>
<br>
<br>
<br>
Modified:<br>
llvm/trunk/lib/Transforms/<wbr>InstCombine/InstCombineCasts.<wbr>cpp<br>
llvm/trunk/test/Transforms/<wbr>InstCombine/cast-mul-select.ll<br>
llvm/trunk/test/Transforms/<wbr>InstCombine/icmp-mul-zext.ll<br>
<br>
Modified: llvm/trunk/lib/Transforms/<wbr>InstCombine/InstCombineCasts.<wbr>cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp?rev=324276&r1=324275&r2=324276&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/llvm/trunk/lib/<wbr>Transforms/InstCombine/<wbr>InstCombineCasts.cpp?rev=<wbr>324276&r1=324275&r2=324276&<wbr>view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/lib/Transforms/<wbr>InstCombine/InstCombineCasts.<wbr>cpp (original)<br>
+++ llvm/trunk/lib/Transforms/<wbr>InstCombine/InstCombineCasts.<wbr>cpp Mon Feb 5 13:50:32 2018<br>
@@ -185,14 +185,8 @@ Value *InstCombiner::<wbr>EvaluateInDifferent<br>
case Instruction::Shl:<br>
case Instruction::UDiv:<br>
case Instruction::URem: {<br>
- Value *LHS, *RHS;<br>
- if (I->getOperand(0) == I->getOperand(1)) {<br>
- // Don't create an unnecessary value if the operands are repeated.<br>
- LHS = RHS = EvaluateInDifferentType(I-><wbr>getOperand(0), Ty, isSigned);<br>
- } else {<br>
- LHS = EvaluateInDifferentType(I-><wbr>getOperand(0), Ty, isSigned);<br>
- RHS = EvaluateInDifferentType(I-><wbr>getOperand(1), Ty, isSigned);<br>
- }<br>
+ Value *LHS = EvaluateInDifferentType(I-><wbr>getOperand(0), Ty, isSigned);<br>
+ Value *RHS = EvaluateInDifferentType(I-><wbr>getOperand(1), Ty, isSigned);<br>
Res = BinaryOperator::Create((<wbr>Instruction::BinaryOps)Opc, LHS, RHS);<br>
break;<br>
}<br>
@@ -326,15 +320,11 @@ static bool canNotEvaluateInType(Value *<br>
assert(!isa<Constant>(V) && "Constant should already be handled.");<br>
if (!isa<Instruction>(V))<br>
return true;<br>
- // We can't extend or shrink something that has multiple uses -- unless those<br>
- // multiple uses are all in the same binop instruction -- doing so would<br>
- // require duplicating the instruction which isn't profitable.<br>
- if (!V->hasOneUse()) {<br>
- if (!match(V->user_back(), m_BinOp()))<br>
- return true;<br>
- if (any_of(V->users(), [&](User *U) { return U != V->user_back(); }))<br>
- return true;<br>
- }<br>
+ // We don't extend or shrink something that has multiple uses -- doing so<br>
+ // would require duplicating the instruction which isn't profitable.<br>
+ if (!V->hasOneUse())<br>
+ return true;<br>
+<br>
return false;<br>
}<br>
<br>
<br>
Modified: llvm/trunk/test/Transforms/<wbr>InstCombine/cast-mul-select.ll<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/cast-mul-select.ll?rev=324276&r1=324275&r2=324276&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/llvm/trunk/test/<wbr>Transforms/InstCombine/cast-<wbr>mul-select.ll?rev=324276&r1=<wbr>324275&r2=324276&view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/test/Transforms/<wbr>InstCombine/cast-mul-select.ll (original)<br>
+++ llvm/trunk/test/Transforms/<wbr>InstCombine/cast-mul-select.ll Mon Feb 5 13:50:32 2018<br>
@@ -47,11 +47,16 @@ define i8 @select2(i1 %cond, i8 %x, i8 %<br>
ret i8 %F<br>
}<br>
<br>
+; The next 3 tests could be handled in instcombine, but evaluating values<br>
+; with multiple uses may be very slow. Let some other pass deal with it.<br>
+<br>
define i32 @eval_trunc_multi_use_in_one_<wbr>inst(i32 %x) {<br>
; CHECK-LABEL: @eval_trunc_multi_use_in_one_<wbr>inst(<br>
-; CHECK-NEXT: [[A:%.*]] = add i32 [[X:%.*]], 15<br>
-; CHECK-NEXT: [[M:%.*]] = mul i32 [[A]], [[A]]<br>
-; CHECK-NEXT: ret i32 [[M]]<br>
+; CHECK-NEXT: [[Z:%.*]] = zext i32 [[X:%.*]] to i64<br>
+; CHECK-NEXT: [[A:%.*]] = add nuw nsw i64 [[Z]], 15<br>
+; CHECK-NEXT: [[M:%.*]] = mul i64 [[A]], [[A]]<br>
+; CHECK-NEXT: [[T:%.*]] = trunc i64 [[M]] to i32<br>
+; CHECK-NEXT: ret i32 [[T]]<br>
;<br>
%z = zext i32 %x to i64<br>
%a = add nsw nuw i64 %z, 15<br>
@@ -62,9 +67,11 @@ define i32 @eval_trunc_multi_use_in_one_<br>
<br>
define i32 @eval_zext_multi_use_in_one_<wbr>inst(i32 %x) {<br>
; CHECK-LABEL: @eval_zext_multi_use_in_one_<wbr>inst(<br>
-; CHECK-NEXT: [[A:%.*]] = and i32 [[X:%.*]], 5<br>
-; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i32 [[A]], [[A]]<br>
-; CHECK-NEXT: ret i32 [[M]]<br>
+; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i16<br>
+; CHECK-NEXT: [[A:%.*]] = and i16 [[T]], 5<br>
+; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i16 [[A]], [[A]]<br>
+; CHECK-NEXT: [[R:%.*]] = zext i16 [[M]] to i32<br>
+; CHECK-NEXT: ret i32 [[R]]<br>
;<br>
%t = trunc i32 %x to i16<br>
%a = and i16 %t, 5<br>
@@ -75,10 +82,12 @@ define i32 @eval_zext_multi_use_in_one_i<br>
<br>
define i32 @eval_sext_multi_use_in_one_<wbr>inst(i32 %x) {<br>
; CHECK-LABEL: @eval_sext_multi_use_in_one_<wbr>inst(<br>
-; CHECK-NEXT: [[A:%.*]] = and i32 [[X:%.*]], 14<br>
-; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i32 [[A]], [[A]]<br>
-; CHECK-NEXT: [[O:%.*]] = or i32 [[M]], -32768<br>
-; CHECK-NEXT: ret i32 [[O]]<br>
+; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i16<br>
+; CHECK-NEXT: [[A:%.*]] = and i16 [[T]], 14<br>
+; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i16 [[A]], [[A]]<br>
+; CHECK-NEXT: [[O:%.*]] = or i16 [[M]], -32768<br>
+; CHECK-NEXT: [[R:%.*]] = sext i16 [[O]] to i32<br>
+; CHECK-NEXT: ret i32 [[R]]<br>
;<br>
%t = trunc i32 %x to i16<br>
%a = and i16 %t, 14<br>
<br>
Modified: llvm/trunk/test/Transforms/<wbr>InstCombine/icmp-mul-zext.ll<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp-mul-zext.ll?rev=324276&r1=324275&r2=324276&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-<wbr>project/llvm/trunk/test/<wbr>Transforms/InstCombine/icmp-<wbr>mul-zext.ll?rev=324276&r1=<wbr>324275&r2=324276&view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/test/Transforms/<wbr>InstCombine/icmp-mul-zext.ll (original)<br>
+++ llvm/trunk/test/Transforms/<wbr>InstCombine/icmp-mul-zext.ll Mon Feb 5 13:50:32 2018<br>
@@ -55,12 +55,13 @@ lor.end:<br>
<br>
define void @PR33765(i8 %beth) {<br>
; CHECK-LABEL: @PR33765(<br>
-; CHECK-NEXT: [[CONV:%.*]] = zext i8 [[BETH:%.*]] to i16<br>
+; CHECK-NEXT: [[CONV:%.*]] = zext i8 [[BETH:%.*]] to i32<br>
; CHECK-NEXT: br i1 false, label [[IF_THEN9:%.*]], label [[IF_THEN9]]<br>
; CHECK: if.then9:<br>
-; CHECK-NEXT: [[MUL:%.*]] = mul nuw i16 [[CONV]], [[CONV]]<br>
+; CHECK-NEXT: [[MUL:%.*]] = mul nuw nsw i32 [[CONV]], [[CONV]]<br>
; CHECK-NEXT: [[TINKY:%.*]] = load i16, i16* @glob, align 2<br>
-; CHECK-NEXT: [[CONV14:%.*]] = and i16 [[TINKY]], [[MUL]]<br>
+; CHECK-NEXT: [[TMP1:%.*]] = trunc i32 [[MUL]] to i16<br>
+; CHECK-NEXT: [[CONV14:%.*]] = and i16 [[TINKY]], [[TMP1]]<br>
; CHECK-NEXT: store i16 [[CONV14]], i16* @glob, align 2<br>
; CHECK-NEXT: ret void<br>
;<br>
<br>
<br>
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</blockquote></div><br></div>