[llvm] r324276 - [InstCombine] don't try to evaluate instructions with >1 use (revert r324014)
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Mon Feb 5 14:01:51 PST 2018
Shouldn't this part of canEvaluateTruncated been changed in the original
patch to avoid the explosion?
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
// These operators can all arbitrarily be extended or truncated.
return canEvaluateTruncated(I->getOperand(0), Ty, IC, CxtI) &&
canEvaluateTruncated(I->getOperand(1), Ty, IC, CxtI);
~Craig
On Mon, Feb 5, 2018 at 1:50 PM, Sanjay Patel via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: spatel
> Date: Mon Feb 5 13:50:32 2018
> New Revision: 324276
>
> URL: http://llvm.org/viewvc/llvm-project?rev=324276&view=rev
> Log:
> [InstCombine] don't try to evaluate instructions with >1 use (revert
> r324014)
>
> This example causes a compile-time explosion:
>
> define i16 @foo(i16 %in) {
> %x = zext i16 %in to i32
> %a1 = mul i32 %x, %x
> %a2 = mul i32 %a1, %a1
> %a3 = mul i32 %a2, %a2
> %a4 = mul i32 %a3, %a3
> %a5 = mul i32 %a4, %a4
> %a6 = mul i32 %a5, %a5
> %a7 = mul i32 %a6, %a6
> %a8 = mul i32 %a7, %a7
> %a9 = mul i32 %a8, %a8
> %a10 = mul i32 %a9, %a9
> %a11 = mul i32 %a10, %a10
> %a12 = mul i32 %a11, %a11
> %a13 = mul i32 %a12, %a12
> %a14 = mul i32 %a13, %a13
> %a15 = mul i32 %a14, %a14
> %a16 = mul i32 %a15, %a15
> %a17 = mul i32 %a16, %a16
> %a18 = mul i32 %a17, %a17
> %a19 = mul i32 %a18, %a18
> %a20 = mul i32 %a19, %a19
> %a21 = mul i32 %a20, %a20
> %a22 = mul i32 %a21, %a21
> %a23 = mul i32 %a22, %a22
> %a24 = mul i32 %a23, %a23
> %T = trunc i32 %a24 to i16
> ret i16 %T
> }
>
>
>
> Modified:
> llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
> llvm/trunk/test/Transforms/InstCombine/cast-mul-select.ll
> llvm/trunk/test/Transforms/InstCombine/icmp-mul-zext.ll
>
> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/
> Transforms/InstCombine/InstCombineCasts.cpp?rev=
> 324276&r1=324275&r2=324276&view=diff
> ============================================================
> ==================
> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp (original)
> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp Mon Feb 5
> 13:50:32 2018
> @@ -185,14 +185,8 @@ Value *InstCombiner::EvaluateInDifferent
> case Instruction::Shl:
> case Instruction::UDiv:
> case Instruction::URem: {
> - Value *LHS, *RHS;
> - if (I->getOperand(0) == I->getOperand(1)) {
> - // Don't create an unnecessary value if the operands are repeated.
> - LHS = RHS = EvaluateInDifferentType(I->getOperand(0), Ty,
> isSigned);
> - } else {
> - LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
> - RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
> - }
> + Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
> + Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
> Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS);
> break;
> }
> @@ -326,15 +320,11 @@ static bool canNotEvaluateInType(Value *
> assert(!isa<Constant>(V) && "Constant should already be handled.");
> if (!isa<Instruction>(V))
> return true;
> - // We can't extend or shrink something that has multiple uses -- unless
> those
> - // multiple uses are all in the same binop instruction -- doing so would
> - // require duplicating the instruction which isn't profitable.
> - if (!V->hasOneUse()) {
> - if (!match(V->user_back(), m_BinOp()))
> - return true;
> - if (any_of(V->users(), [&](User *U) { return U != V->user_back(); }))
> - return true;
> - }
> + // We don't extend or shrink something that has multiple uses -- doing
> so
> + // would require duplicating the instruction which isn't profitable.
> + if (!V->hasOneUse())
> + return true;
> +
> return false;
> }
>
>
> Modified: llvm/trunk/test/Transforms/InstCombine/cast-mul-select.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/InstCombine/cast-mul-select.ll?rev=324276&r1=
> 324275&r2=324276&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/InstCombine/cast-mul-select.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/cast-mul-select.ll Mon Feb 5
> 13:50:32 2018
> @@ -47,11 +47,16 @@ define i8 @select2(i1 %cond, i8 %x, i8 %
> ret i8 %F
> }
>
> +; The next 3 tests could be handled in instcombine, but evaluating values
> +; with multiple uses may be very slow. Let some other pass deal with it.
> +
> define i32 @eval_trunc_multi_use_in_one_inst(i32 %x) {
> ; CHECK-LABEL: @eval_trunc_multi_use_in_one_inst(
> -; CHECK-NEXT: [[A:%.*]] = add i32 [[X:%.*]], 15
> -; CHECK-NEXT: [[M:%.*]] = mul i32 [[A]], [[A]]
> -; CHECK-NEXT: ret i32 [[M]]
> +; CHECK-NEXT: [[Z:%.*]] = zext i32 [[X:%.*]] to i64
> +; CHECK-NEXT: [[A:%.*]] = add nuw nsw i64 [[Z]], 15
> +; CHECK-NEXT: [[M:%.*]] = mul i64 [[A]], [[A]]
> +; CHECK-NEXT: [[T:%.*]] = trunc i64 [[M]] to i32
> +; CHECK-NEXT: ret i32 [[T]]
> ;
> %z = zext i32 %x to i64
> %a = add nsw nuw i64 %z, 15
> @@ -62,9 +67,11 @@ define i32 @eval_trunc_multi_use_in_one_
>
> define i32 @eval_zext_multi_use_in_one_inst(i32 %x) {
> ; CHECK-LABEL: @eval_zext_multi_use_in_one_inst(
> -; CHECK-NEXT: [[A:%.*]] = and i32 [[X:%.*]], 5
> -; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i32 [[A]], [[A]]
> -; CHECK-NEXT: ret i32 [[M]]
> +; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i16
> +; CHECK-NEXT: [[A:%.*]] = and i16 [[T]], 5
> +; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i16 [[A]], [[A]]
> +; CHECK-NEXT: [[R:%.*]] = zext i16 [[M]] to i32
> +; CHECK-NEXT: ret i32 [[R]]
> ;
> %t = trunc i32 %x to i16
> %a = and i16 %t, 5
> @@ -75,10 +82,12 @@ define i32 @eval_zext_multi_use_in_one_i
>
> define i32 @eval_sext_multi_use_in_one_inst(i32 %x) {
> ; CHECK-LABEL: @eval_sext_multi_use_in_one_inst(
> -; CHECK-NEXT: [[A:%.*]] = and i32 [[X:%.*]], 14
> -; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i32 [[A]], [[A]]
> -; CHECK-NEXT: [[O:%.*]] = or i32 [[M]], -32768
> -; CHECK-NEXT: ret i32 [[O]]
> +; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i16
> +; CHECK-NEXT: [[A:%.*]] = and i16 [[T]], 14
> +; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i16 [[A]], [[A]]
> +; CHECK-NEXT: [[O:%.*]] = or i16 [[M]], -32768
> +; CHECK-NEXT: [[R:%.*]] = sext i16 [[O]] to i32
> +; CHECK-NEXT: ret i32 [[R]]
> ;
> %t = trunc i32 %x to i16
> %a = and i16 %t, 14
>
> Modified: llvm/trunk/test/Transforms/InstCombine/icmp-mul-zext.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/InstCombine/icmp-mul-zext.ll?rev=324276&r1=
> 324275&r2=324276&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/InstCombine/icmp-mul-zext.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/icmp-mul-zext.ll Mon Feb 5
> 13:50:32 2018
> @@ -55,12 +55,13 @@ lor.end:
>
> define void @PR33765(i8 %beth) {
> ; CHECK-LABEL: @PR33765(
> -; CHECK-NEXT: [[CONV:%.*]] = zext i8 [[BETH:%.*]] to i16
> +; CHECK-NEXT: [[CONV:%.*]] = zext i8 [[BETH:%.*]] to i32
> ; CHECK-NEXT: br i1 false, label [[IF_THEN9:%.*]], label [[IF_THEN9]]
> ; CHECK: if.then9:
> -; CHECK-NEXT: [[MUL:%.*]] = mul nuw i16 [[CONV]], [[CONV]]
> +; CHECK-NEXT: [[MUL:%.*]] = mul nuw nsw i32 [[CONV]], [[CONV]]
> ; CHECK-NEXT: [[TINKY:%.*]] = load i16, i16* @glob, align 2
> -; CHECK-NEXT: [[CONV14:%.*]] = and i16 [[TINKY]], [[MUL]]
> +; CHECK-NEXT: [[TMP1:%.*]] = trunc i32 [[MUL]] to i16
> +; CHECK-NEXT: [[CONV14:%.*]] = and i16 [[TINKY]], [[TMP1]]
> ; CHECK-NEXT: store i16 [[CONV14]], i16* @glob, align 2
> ; CHECK-NEXT: ret void
> ;
>
>
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