[llvm-commits] [llvm] r61985 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/cast.ll test/Transforms/InstCombine/icmp.ll
Evan Cheng
echeng at apple.com
Mon Jan 12 23:39:54 PST 2009
I think it's failing in a lazy compilation callback. Dan, is that right?
Evan
On Jan 12, 2009, at 11:09 PM, Chris Lattner wrote:
>
> On Jan 12, 2009, at 5:18 PM, Dan Gohman wrote:
>
>> Hi Chris,
>>
>> The recent 176.gcc JIT regression on darwin x86-32 isolated down to
>> this commit. Can you investigate?
>
> Absolutely.
>
> -Chris
>
>>
>>
>> Thanks,
>>
>> Dan
>>
>> On Jan 8, 2009, at 11:47 PM, Chris Lattner wrote:
>>
>>> Author: lattner
>>> Date: Fri Jan 9 01:47:06 2009
>>> New Revision: 61985
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=61985&view=rev
>>> Log:
>>> Implement rdar://6480391, extending of equality icmp's to avoid a
>>> truncation.
>>> I noticed this in the code compiled for a routine using std::map,
>>> which produced
>>> this code:
>>> %25 = tail call i32 @memcmp(i8* %24, i8* %23, i32 6) nounwind
>>> readonly
>>> %.lobit.i = lshr i32 %25, 31 ; <i32> [#uses=1]
>>> %tmp.i = trunc i32 %.lobit.i to i8 ; <i8> [#uses=1]
>>> %toBool = icmp eq i8 %tmp.i, 0 ; <i1> [#uses=1]
>>> br i1 %toBool, label %bb3, label %bb4
>>> which compiled to:
>>>
>>> call L_memcmp$stub
>>> shrl $31, %eax
>>> testb %al, %al
>>> jne LBB1_11 ##
>>>
>>> with this change, we compile it to:
>>>
>>> call L_memcmp$stub
>>> testl %eax, %eax
>>> js LBB1_11
>>>
>>> This triggers all the time in common code, with patters like this:
>>>
>>> %169 = and i32 %ply, 1 ; <i32> [#uses=1]
>>> %170 = trunc i32 %169 to i8 ; <i8> [#uses=1]
>>> %toBool = icmp ne i8 %170, 0 ; <i1> [#uses=1]
>>>
>>> %7 = lshr i32 %6, 24 ; <i32> [#uses=1]
>>> %9 = trunc i32 %7 to i8 ; <i8> [#uses=1]
>>> %10 = icmp ne i8 %9, 0 ; <i1> [#uses=1]
>>>
>>> etc
>>>
>>>
>>> Modified:
>>> llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
>>> llvm/trunk/test/Transforms/InstCombine/cast.ll
>>> llvm/trunk/test/Transforms/InstCombine/icmp.ll
>>>
>>> Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=61985&r1=61984&r2=61985&view=diff
>>>
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> ====================================================================
>>> --- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
>>> (original)
>>> +++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Fri
>>> Jan 9 01:47:06 2009
>>> @@ -6343,6 +6343,28 @@
>>> const APInt &RHSV = RHS->getValue();
>>>
>>> switch (LHSI->getOpcode()) {
>>> + case Instruction::Trunc:
>>> + if (ICI.isEquality() && LHSI->hasOneUse()) {
>>> + // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|
>>> highbits if all
>>> + // of the high bits truncated out of x are known.
>>> + unsigned DstBits = LHSI->getType()->getPrimitiveSizeInBits(),
>>> + SrcBits = LHSI->getOperand(0)->getType()-
>>>> getPrimitiveSizeInBits();
>>> + APInt Mask(APInt::getHighBitsSet(SrcBits, SrcBits-DstBits));
>>> + APInt KnownZero(SrcBits, 0), KnownOne(SrcBits, 0);
>>> + ComputeMaskedBits(LHSI->getOperand(0), Mask, KnownZero,
>>> KnownOne);
>>> +
>>> + // If all the high bits are known, we can do this xform.
>>> + if ((KnownZero|KnownOne).countLeadingOnes() >= SrcBits-
>>> DstBits) {
>>> + // Pull in the high bits from known-ones set.
>>> + APInt NewRHS(RHS->getValue());
>>> + NewRHS.zext(SrcBits);
>>> + NewRHS |= KnownOne;
>>> + return new ICmpInst(ICI.getPredicate(), LHSI-
>>> >getOperand(0),
>>> + ConstantInt::get(NewRHS));
>>> + }
>>> + }
>>> + break;
>>> +
>>> case Instruction::Xor: // (icmp pred (xor X, XorCST), CI)
>>> if (ConstantInt *XorCST = dyn_cast<ConstantInt>(LHSI-
>>>> getOperand(1))) {
>>> // If this is a comparison that tests the signbit (X < 0) or
>>> (x > -1),
>>>
>>> Modified: llvm/trunk/test/Transforms/InstCombine/cast.ll
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/cast.ll?rev=61985&r1=61984&r2=61985&view=diff
>>>
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> ====================================================================
>>> --- llvm/trunk/test/Transforms/InstCombine/cast.ll (original)
>>> +++ llvm/trunk/test/Transforms/InstCombine/cast.ll Fri Jan 9
>>> 01:47:06 2009
>>> @@ -1,7 +1,5 @@
>>> ; Tests to make sure elimination of casts is working correctly
>>> -; RUN: llvm-as < %s | opt -instcombine | llvm-dis | \
>>> -; RUN: grep %c | notcast
>>> -; END.
>>> +; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep %c |
>>> notcast
>>>
>>> @inbuf = external global [32832 x i8] ; <[32832 x i8]*>
>>> [#uses=1]
>>>
>>> @@ -238,3 +236,21 @@
>>> ret i16 %c2
>>> }
>>>
>>> +; icmp sgt i32 %a, -1
>>> +; rdar://6480391
>>> +define i1 @test36(i32 %a) {
>>> + %b = lshr i32 %a, 31
>>> + %c = trunc i32 %b to i8
>>> + %d = icmp eq i8 %c, 0
>>> + ret i1 %d
>>> +}
>>> +
>>> +; ret i1 false
>>> +define i1 @test37(i32 %a) {
>>> + %b = lshr i32 %a, 31
>>> + %c = or i32 %b, 512
>>> + %d = trunc i32 %c to i8
>>> + %e = icmp eq i8 %d, 11
>>> + ret i1 %e
>>> +}
>>> +
>>>
>>> Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=61985&r1=61984&r2=61985&view=diff
>>>
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> =
>>> ====================================================================
>>> --- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
>>> +++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Fri Jan 9
>>> 01:47:06 2009
>>> @@ -1,5 +1,4 @@
>>> ; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep icmp
>>> -; END.
>>>
>>> define i32 @test1(i32 %X) {
>>> entry:
>>>
>>>
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