[llvm] r335020 - [SimplifyIndVars] Eliminate redundant truncs
Mikael Holmén via llvm-commits
llvm-commits at lists.llvm.org
Thu Jun 28 00:58:01 PDT 2018
On 06/28/2018 09:47 AM, Maxim Kazantsev wrote:
> Interesting. A user in block unreachable from entry, I didn't think we can end up with something like this. :) I'll come up with a fix soon. Thanks for test!
Yes I don't know how many problems I've stumbled upon now due to weird
code in blocks that are unreachable from entry that several passes then
flips out on.
I hope the gain from allowing such code is huge since there are
certainly many problems with it.
Thanks,
Mikael
>
> -- Max
>
> -----Original Message-----
> From: Mikael Holmén [mailto:mikael.holmen at ericsson.com]
> Sent: Thursday, June 28, 2018 2:34 PM
> To: Maxim Kazantsev <max.kazantsev at azul.com>
> Cc: llvm-commits at lists.llvm.org
> Subject: Re: [llvm] r335020 - [SimplifyIndVars] Eliminate redundant truncs
>
> Hi Max,
>
> With
>
> opt -S -o - bbi-15696.ll -indvars
>
> I trigger one of the new asserts in this patch:
>
> opt: ../lib/Transforms/Utils/SimplifyIndVar.cpp:540: bool (anonymous namespace)::SimplifyIndvar::eliminateTrunc(llvm::TruncInst *): Assertion
> `L->contains(ICI->getParent()) && "LCSSA form broken?"' failed.
> Stack dump:
> 0. Program arguments: build-all/bin/opt -S -o - bbi-15696.ll -indvars
> 1. Running pass 'Function Pass Manager' on module 'bbi-15696.ll'.
> 2. Running pass 'Loop Pass Manager' on function '@f3'
> 3. Running pass 'Induction Variable Simplification' on basic block
> '%bb1'
> #0 0x0000000001ff1b44 PrintStackTraceSignalHandler(void*)
> (build-all/bin/opt+0x1ff1b44)
> #1 0x0000000001fefdb0 llvm::sys::RunSignalHandlers()
> (build-all/bin/opt+0x1fefdb0)
> #2 0x0000000001ff1ea8 SignalHandler(int) (build-all/bin/opt+0x1ff1ea8)
> #3 0x00007f314bd38330 __restore_rt
> (/lib/x86_64-linux-gnu/libpthread.so.0+0x10330)
> #4 0x00007f314a927c37 gsignal
> /build/eglibc-ripdx6/eglibc-2.19/signal/../nptl/sysdeps/unix/sysv/linux/raise.c:56:0
> #5 0x00007f314a92b028 abort
> /build/eglibc-ripdx6/eglibc-2.19/stdlib/abort.c:91:0
> #6 0x00007f314a920bf6 __assert_fail_base
> /build/eglibc-ripdx6/eglibc-2.19/assert/assert.c:92:0
> #7 0x00007f314a920ca2 (/lib/x86_64-linux-gnu/libc.so.6+0x2fca2)
> #8 0x00000000020d2906 (anonymous
> namespace)::SimplifyIndvar::eliminateIVUser(llvm::Instruction*,
> llvm::Instruction*) (build-all/bin/opt+0x20d2906)
> #9 0x00000000020cf81b llvm::simplifyUsersOfIV(llvm::PHINode*,
> llvm::ScalarEvolution*, llvm::DominatorTree*, llvm::LoopInfo*, llvm::SmallVectorImpl<llvm::WeakTrackingVH>&, llvm::SCEVExpander&,
> llvm::IVVisitor*) (build-all/bin/opt+0x20cf81b)
> #10 0x0000000001ded2c1 (anonymous
> namespace)::IndVarSimplify::run(llvm::Loop*) (build-all/bin/opt+0x1ded2c1)
> #11 0x0000000001df202c (anonymous
> namespace)::IndVarSimplifyLegacyPass::runOnLoop(llvm::Loop*,
> llvm::LPPassManager&) (build-all/bin/opt+0x1df202c)
> #12 0x0000000001533995
> llvm::LPPassManager::runOnFunction(llvm::Function&)
> (build-all/bin/opt+0x1533995)
> #13 0x0000000001a7f5da
> llvm::FPPassManager::runOnFunction(llvm::Function&)
> (build-all/bin/opt+0x1a7f5da)
> #14 0x0000000001a7f838 llvm::FPPassManager::runOnModule(llvm::Module&)
> (build-all/bin/opt+0x1a7f838)
> #15 0x0000000001a7fd6d llvm::legacy::PassManagerImpl::run(llvm::Module&)
> (build-all/bin/opt+0x1a7fd6d)
> #16 0x0000000000744f4c main (build-all/bin/opt+0x744f4c)
> #17 0x00007f314a912f45 __libc_start_main
> /build/eglibc-ripdx6/eglibc-2.19/csu/libc-start.c:321:0
> #18 0x000000000072e2ad _start (build-all/bin/opt+0x72e2ad) Abort
>
> When the assertion fails TI is
> %_tmp15 = trunc i32 %e.5.0 to i16
> and ICI is
> %_tmp24 = icmp slt i16 %_tmp15, 0
> and L is
> Loop at depth 1 containing:
> %bb1<header>,%bb2,%bb3,%bb4,%bb6<latch><exiting>
>
> %bb5 which contains the icmp is only reached from itself
>
> bb5: ; preds = %bb5, %bb5
> %_tmp24 = icmp slt i16 %_tmp15, 0
> br i1 %_tmp24, label %bb5, label %bb5
>
> Regards,
> Mikael
>
> On 06/19/2018 06:48 AM, Max Kazantsev via llvm-commits wrote:
>> Author: mkazantsev
>> Date: Mon Jun 18 21:48:34 2018
>> New Revision: 335020
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=335020&view=rev
>> Log:
>> [SimplifyIndVars] Eliminate redundant truncs
>>
>> This patch adds logic to deal with the following constructions:
>>
>> %iv = phi i64 ...
>> %trunc = trunc i64 %iv to i32
>> %cmp = icmp <pred> i32 %trunc, %invariant
>>
>> Replacing it with
>> %iv = phi i64 ...
>> %cmp = icmp <pred> i64 %iv, sext/zext(%invariant)
>>
>> In case if it is legal. Specifically, if `%iv` has signed comparison
>> users, it is required that `sext(trunc(%iv)) == %iv`, and if it has
>> unsigned comparison uses then we require `zext(trunc(%iv)) == %iv`.
>> The current implementation bails if `%trunc` has other uses than
>> `icmp`, but in theory we can handle more cases here (e.g. if the user of trunc is bitcast).
>>
>> Differential Revision: https://reviews.llvm.org/D47928 Reviewed By:
>> reames
>>
>> Added:
>> llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll
>> Modified:
>> llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
>> llvm/trunk/test/Transforms/IndVarSimplify/ada-loops.ll
>> llvm/trunk/test/Transforms/IndVarSimplify/widen-loop-comp.ll
>>
>> Modified: llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/Si
>> mplifyIndVar.cpp?rev=335020&r1=335019&r2=335020&view=diff
>> ======================================================================
>> ========
>> --- llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp Mon Jun 18
>> +++ 21:48:34 2018
>> @@ -81,6 +81,7 @@ namespace {
>> bool replaceIVUserWithLoopInvariant(Instruction *UseInst);
>>
>> bool eliminateOverflowIntrinsic(CallInst *CI);
>> + bool eliminateTrunc(TruncInst *TI);
>> bool eliminateIVUser(Instruction *UseInst, Instruction *IVOperand);
>> bool makeIVComparisonInvariant(ICmpInst *ICmp, Value *IVOperand);
>> void eliminateIVComparison(ICmpInst *ICmp, Value *IVOperand); @@
>> -494,6 +495,93 @@ bool SimplifyIndvar::eliminateOverflowIn
>> return true;
>> }
>>
>> +bool SimplifyIndvar::eliminateTrunc(TruncInst *TI) {
>> + // It is always legal to replace
>> + // icmp <pred> i32 trunc(iv), n
>> + // with
>> + // icmp <pred> i64 sext(trunc(iv)), sext(n), if pred is signed predicate.
>> + // Or with
>> + // icmp <pred> i64 zext(trunc(iv)), zext(n), if pred is unsigned predicate.
>> + // Or with either of these if pred is an equality predicate.
>> + //
>> + // If we can prove that iv == sext(trunc(iv)) or iv ==
>> +zext(trunc(iv)) for
>> + // every comparison which uses trunc, it means that we can replace
>> +each of
>> + // them with comparison of iv against sext/zext(n). We no longer
>> +need trunc
>> + // after that.
>> + //
>> + // TODO: Should we do this if we can widen *some* comparisons, but
>> +not all
>> + // of them? Sometimes it is enough to enable other optimizations,
>> +but the
>> + // trunc instruction will stay in the loop.
>> + Value *IV = TI->getOperand(0);
>> + Type *IVTy = IV->getType();
>> + const SCEV *IVSCEV = SE->getSCEV(IV);
>> + const SCEV *TISCEV = SE->getSCEV(TI);
>> +
>> + // Check if iv == zext(trunc(iv)) and if iv == sext(trunc(iv)). If
>> + so, we can // get rid of trunc bool DoesSExtCollapse = false;
>> + bool DoesZExtCollapse = false; if (IVSCEV ==
>> + SE->getSignExtendExpr(TISCEV, IVTy))
>> + DoesSExtCollapse = true;
>> + if (IVSCEV == SE->getZeroExtendExpr(TISCEV, IVTy))
>> + DoesZExtCollapse = true;
>> +
>> + // If neither sext nor zext does collapse, it is not profitable to
>> + do any // transform. Bail.
>> + if (!DoesSExtCollapse && !DoesZExtCollapse)
>> + return false;
>> +
>> + // Collect users of the trunc that look like comparisons against invariants.
>> + // Bail if we find something different.
>> + SmallVector<ICmpInst *, 4> ICmpUsers; for (auto *U : TI->users())
>> + {
>> + if (ICmpInst *ICI = dyn_cast<ICmpInst>(U)) {
>> + if (ICI->getOperand(0) == TI && L->isLoopInvariant(ICI->getOperand(1))) {
>> + assert(L->contains(ICI->getParent()) && "LCSSA form broken?");
>> + // If we cannot get rid of trunc, bail.
>> + if (ICI->isSigned() && !DoesSExtCollapse)
>> + return false;
>> + if (ICI->isUnsigned() && !DoesZExtCollapse)
>> + return false;
>> + // For equality, either signed or unsigned works.
>> + ICmpUsers.push_back(ICI);
>> + } else
>> + return false;
>> + } else
>> + return false;
>> + }
>> +
>> + // Replace all comparisons against trunc with comparisons against IV.
>> + for (auto *ICI : ICmpUsers) {
>> + auto *Op1 = ICI->getOperand(1);
>> + Instruction *Ext = nullptr;
>> + // For signed/unsigned predicate, replace the old comparison with comparison
>> + // of immediate IV against sext/zext of the invariant argument. If we can
>> + // use either sext or zext (i.e. we are dealing with equality predicate),
>> + // then prefer zext as a more canonical form.
>> + // TODO: If we see a signed comparison which can be turned into unsigned,
>> + // we can do it here for canonicalization purposes.
>> + if (ICI->isUnsigned() || (ICI->isEquality() && DoesZExtCollapse)) {
>> + assert(DoesZExtCollapse && "Unprofitable zext?");
>> + Ext = new ZExtInst(Op1, IVTy, "zext", ICI);
>> + } else {
>> + assert(DoesSExtCollapse && "Unprofitable sext?");
>> + Ext = new SExtInst(Op1, IVTy, "sext", ICI);
>> + }
>> + bool Changed;
>> + L->makeLoopInvariant(Ext, Changed);
>> + (void)Changed;
>> + ICmpInst *NewICI = new ICmpInst(ICI, ICI->getPredicate(), IV, Ext);
>> + ICI->replaceAllUsesWith(NewICI);
>> + DeadInsts.emplace_back(ICI);
>> + }
>> +
>> + // Trunc no longer needed.
>> + TI->replaceAllUsesWith(UndefValue::get(TI->getType()));
>> + DeadInsts.emplace_back(TI);
>> + return true;
>> +}
>> +
>> /// Eliminate an operation that consumes a simple IV and has no observable
>> /// side-effect given the range of IV values. IVOperand is guaranteed SCEVable,
>> /// but UseInst may not be.
>> @@ -518,6 +606,10 @@ bool SimplifyIndvar::eliminateIVUser(Ins
>> if (eliminateOverflowIntrinsic(CI))
>> return true;
>>
>> + if (auto *TI = dyn_cast<TruncInst>(UseInst))
>> + if (eliminateTrunc(TI))
>> + return true;
>> +
>> if (eliminateIdentitySCEV(UseInst, IVOperand))
>> return true;
>>
>>
>> Modified: llvm/trunk/test/Transforms/IndVarSimplify/ada-loops.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarS
>> implify/ada-loops.ll?rev=335020&r1=335019&r2=335020&view=diff
>> ======================================================================
>> ========
>> --- llvm/trunk/test/Transforms/IndVarSimplify/ada-loops.ll (original)
>> +++ llvm/trunk/test/Transforms/IndVarSimplify/ada-loops.ll Mon Jun 18
>> +++ 21:48:34 2018
>> @@ -10,12 +10,17 @@
>> ; don't check that phis are "folded together" because that is a job
>> ; for loop strength reduction. But indvars must remove sext, zext, and add i8.
>> ;
>> -; CHECK-NOT: {{sext|zext|add i8}}
>>
>> ; ModuleID = 'ada.bc'
>> target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-n8:16:32"
>> target triple = "i686-pc-linux-gnu"
>>
>> +; CHECK-LABEL: @kinds__sbytezero
>> +; CHECK: bb.thread:
>> +; CHECK: sext
>> +; CHECK: bb:
>> +; CHECK-NOT: {{sext i8|zext i8|add i8|trunc}}
>> +
>> define void @kinds__sbytezero([256 x i32]* nocapture %a) nounwind {
>> bb.thread:
>> %tmp46 = getelementptr [256 x i32], [256 x i32]* %a, i32 0, i32 0 ; <i32*> [#uses=1]
>> @@ -36,6 +41,8 @@ return: ; preds = %bb
>> ret void
>> }
>>
>> +; CHECK-LABEL: @kinds__ubytezero
>> +
>> define void @kinds__ubytezero([256 x i32]* nocapture %a) nounwind {
>> bb.thread:
>> %tmp35 = getelementptr [256 x i32], [256 x i32]* %a, i32 0, i32 0 ; <i32*> [#uses=1]
>>
>> Added: llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarS
>> implify/eliminate-trunc.ll?rev=335020&view=auto
>> ======================================================================
>> ========
>> --- llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll
>> (added)
>> +++ llvm/trunk/test/Transforms/IndVarSimplify/eliminate-trunc.ll Mon
>> +++ Jun 18 21:48:34 2018
>> @@ -0,0 +1,486 @@
>> +; NOTE: Assertions have been autogenerated by
>> +utils/update_test_checks.py ; RUN: opt -indvars -S < %s | FileCheck
>> +%s
>> +
>> +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
>> +target triple = "x86_64-unknown-linux-gnu"
>> +
>> +; General case: without extra knowledge, trunc cannot be eliminated.
>> +define void @test_00(i64 %start, i32 %n) { ; ; CHECK-LABEL: @test_00(
>> +; CHECK-NEXT: entry:
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1
>> +; CHECK-NEXT: [[NARROW_IV:%.*]] = trunc i64 [[IV]] to i32
>> +; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[NARROW_IV]], [[N:%.*]]
>> +; CHECK-NEXT: br i1 [[CMP]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ %start, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp slt i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +
>> +define void @test_01(i32 %n) {
>> +;
>> +; CHECK-LABEL: @test_01(
>> +; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[N:%.*]] to i64
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[TMP0:%.*]] = icmp slt i64 [[IV]], [[SEXT]]
>> +; CHECK-NEXT: br i1 [[TMP0]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp slt i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Max value at which we can eliminate trunc: SINT_MAX - 1.
>> +define void @test_02(i32 %n) {
>> +;
>> +; CHECK-LABEL: @test_02(
>> +; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[N:%.*]] to i64
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 2147483646, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[TMP0:%.*]] = icmp slt i64 [[IV]], [[SEXT]]
>> +; CHECK-NEXT: br i1 [[TMP0]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ 2147483646, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp slt i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; If we start from SINT_MAX then the predicate is always false.
>> +define void @test_03(i32 %n) {
>> +;
>> +; CHECK-LABEL: @test_03(
>> +; CHECK-NEXT: entry:
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: br i1 false, label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [2147483647, %entry], [%iv.next, %loop]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp slt i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Minimum value at which we can apply the transform: SINT_MIN + 1.
>> +define void @test_04(i32 %n) {
>> +;
>> +; CHECK-LABEL: @test_04(
>> +; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[N:%.*]] to i64
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ -2147483647, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[TMP0:%.*]] = icmp slt i64 [[IV]], [[SEXT]]
>> +; CHECK-NEXT: br i1 [[TMP0]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ -2147483647, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp slt i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; FIXME: Harmful LFTR should be thrown away.
>> +define void @test_05(i32 %n) {
>> +;
>> +; CHECK-LABEL: @test_05(
>> +; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[N:%.*]], 1
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ -2147483648, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[LFTR_WIDEIV:%.*]] = trunc i64 [[IV_NEXT]] to i32
>> +; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i32 [[LFTR_WIDEIV]], [[TMP0]]
>> +; CHECK-NEXT: br i1 [[EXITCOND]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ -2147483648, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp slt i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Trunc changes the actual value of the IV, so it is invalid to remove it: SINT_MIN - 1.
>> +define void @test_06(i32 %n) {
>> +;
>> +; CHECK-LABEL: @test_06(
>> +; CHECK-NEXT: entry:
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ -2147483649, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[NARROW_IV:%.*]] = trunc i64 [[IV]] to i32
>> +; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[NARROW_IV]], [[N:%.*]]
>> +; CHECK-NEXT: br i1 [[CMP]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ -2147483649, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp slt i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; General case: without extra knowledge, trunc cannot be eliminated.
>> +define void @test_00_unsigned(i64 %start, i32 %n) { ; CHECK-LABEL:
>> + at test_00_unsigned( ; CHECK-NEXT: entry:
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1
>> +; CHECK-NEXT: [[NARROW_IV:%.*]] = trunc i64 [[IV]] to i32
>> +; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[NARROW_IV]], [[N:%.*]]
>> +; CHECK-NEXT: br i1 [[CMP]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ %start, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp ult i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; FIXME: Harmful LFTR should be thrown away.
>> +define void @test_01_unsigned(i32 %n) { ; CHECK-LABEL:
>> + at test_01_unsigned( ; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[N:%.*]], 1
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[LFTR_WIDEIV:%.*]] = trunc i64 [[IV_NEXT]] to i32
>> +; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i32 [[LFTR_WIDEIV]], [[TMP0]]
>> +; CHECK-NEXT: br i1 [[EXITCOND]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp ult i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Max value at which we can eliminate trunc: UINT_MAX - 1.
>> +define void @test_02_unsigned(i32 %n) { ; CHECK-LABEL:
>> + at test_02_unsigned( ; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[N:%.*]] to i64
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 4294967294, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i64 [[IV]], [[ZEXT]]
>> +; CHECK-NEXT: br i1 [[TMP0]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ 4294967294, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp ult i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; If we start from UINT_MAX then the predicate is always false.
>> +define void @test_03_unsigned(i32 %n) { ; CHECK-LABEL:
>> + at test_03_unsigned( ; CHECK-NEXT: entry:
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: br i1 false, label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ 4294967295, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp ult i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Minimum value at which we can apply the transform: UINT_MIN.
>> +define void @test_04_unsigned(i32 %n) { ; CHECK-LABEL:
>> + at test_04_unsigned( ; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[N:%.*]], 1
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[LFTR_WIDEIV:%.*]] = trunc i64 [[IV_NEXT]] to i32
>> +; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i32 [[LFTR_WIDEIV]], [[TMP0]]
>> +; CHECK-NEXT: br i1 [[EXITCOND]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp ult i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Start from 1.
>> +define void @test_05_unsigned(i32 %n) { ; CHECK-LABEL:
>> + at test_05_unsigned( ; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[N:%.*]] to i64
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 1, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i64 [[IV]], [[ZEXT]]
>> +; CHECK-NEXT: br i1 [[TMP0]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ 1, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp ult i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Trunc changes the actual value of the IV, so it is invalid to remove it: UINT_MIN - 1.
>> +define void @test_06_unsigned(i32 %n) { ; CHECK-LABEL:
>> + at test_06_unsigned( ; CHECK-NEXT: entry:
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ -1, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[NARROW_IV:%.*]] = trunc i64 [[IV]] to i32
>> +; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[NARROW_IV]], [[N:%.*]]
>> +; CHECK-NEXT: br i1 [[CMP]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ -1, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp ult i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Do not eliminate trunc if it is used by something different from icmp.
>> +define void @test_07(i32* %p, i32 %n) { ; CHECK-LABEL: @test_07( ;
>> +CHECK-NEXT: entry:
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[NARROW_IV:%.*]] = trunc i64 [[IV]] to i32
>> +; CHECK-NEXT: store i32 [[NARROW_IV]], i32* [[P:%.*]]
>> +; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[NARROW_IV]], [[N:%.*]]
>> +; CHECK-NEXT: br i1 [[CMP]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + store i32 %narrow.iv, i32* %p
>> + %cmp = icmp slt i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Check that we can eliminate both signed and unsigned compare.
>> +define void @test_08(i32 %n) {
>> +; CHECK-LABEL: @test_08(
>> +; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[N:%.*]] to i64
>> +; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[N]] to i64
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 1, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[TMP0:%.*]] = icmp slt i64 [[IV]], [[SEXT]]
>> +; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i64 [[IV]], [[ZEXT]]
>> +; CHECK-NEXT: [[CMP:%.*]] = and i1 [[TMP0]], [[TMP1]]
>> +; CHECK-NEXT: br i1 [[CMP]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ 1, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp1 = icmp slt i32 %narrow.iv, %n
>> + %cmp2 = icmp ult i32 %narrow.iv, %n
>> + %cmp = and i1 %cmp1, %cmp2
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Widen NE as unsigned.
>> +define void @test_09(i32 %n) {
>> +; CHECK-LABEL: @test_09(
>> +; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[N:%.*]] to i64
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[TMP0:%.*]] = icmp ne i64 [[IV]], [[ZEXT]]
>> +; CHECK-NEXT: br i1 [[TMP0]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %cmp = icmp ne i32 %narrow.iv, %n
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>> +
>> +; Widen NE as signed.
>> +define void @test_10(i32 %n) {
>> +; CHECK-LABEL: @test_10(
>> +; CHECK-NEXT: entry:
>> +; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[N:%.*]] to i64
>> +; CHECK-NEXT: br label [[LOOP:%.*]]
>> +; CHECK: loop:
>> +; CHECK-NEXT: [[IV:%.*]] = phi i64 [ -100, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
>> +; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
>> +; CHECK-NEXT: [[TMP0:%.*]] = icmp ne i64 [[IV]], [[SEXT]]
>> +; CHECK-NEXT: [[NEGCMP:%.*]] = icmp slt i64 [[IV]], -10
>> +; CHECK-NEXT: [[CMP:%.*]] = and i1 [[TMP0]], [[NEGCMP]]
>> +; CHECK-NEXT: br i1 [[CMP]], label [[LOOP]], label [[EXIT:%.*]]
>> +; CHECK: exit:
>> +; CHECK-NEXT: ret void
>> +;
>> +entry:
>> + br label %loop
>> +loop:
>> + %iv = phi i64 [ -100, %entry ], [ %iv.next, %loop ]
>> + %iv.next = add i64 %iv, 1
>> + %narrow.iv = trunc i64 %iv to i32
>> + %trunccmp = icmp ne i32 %narrow.iv, %n
>> + %negcmp = icmp slt i64 %iv, -10
>> + %cmp = and i1 %trunccmp, %negcmp
>> + br i1 %cmp, label %loop, label %exit
>> +exit:
>> + ret void
>> +}
>>
>> Modified: llvm/trunk/test/Transforms/IndVarSimplify/widen-loop-comp.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarS
>> implify/widen-loop-comp.ll?rev=335020&r1=335019&r2=335020&view=diff
>> ======================================================================
>> ========
>> --- llvm/trunk/test/Transforms/IndVarSimplify/widen-loop-comp.ll
>> (original)
>> +++ llvm/trunk/test/Transforms/IndVarSimplify/widen-loop-comp.ll Mon
>> +++ Jun 18 21:48:34 2018
>> @@ -332,12 +332,12 @@ define i32 @test10(i32 %v) {
>> br label %loop
>>
>> loop:
>> +; CHECK: [[WIDE_V:%[a-z0-9]+]] = sext i32 %v to i64
>> ; CHECK: loop:
>> ; CHECK: %indvars.iv = phi i64 [ %indvars.iv.next, %loop ], [ 0, %entry ]
>> ; CHECK: %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
>> ; CHECK: [[MUL:%[a-z0-9]+]] = mul nsw i64 %indvars.iv, -1 -; CHECK:
>> [[MUL_TRUNC:%[a-z0-9]+]] = trunc i64 [[MUL]] to i32 -; CHECK:
>> [[CMP:%[a-z0-9]+]] = icmp eq i32 [[MUL_TRUNC]], %v
>> +; CHECK: [[CMP:%[a-z0-9]+]] = icmp eq i64 [[MUL]], [[WIDE_V]]
>> ; CHECK: call void @consume.i1(i1 [[CMP]])
>>
>> %i = phi i32 [ 0, %entry ], [ %i.inc, %loop ]
>>
>>
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