[llvm] 10aa7ea - [CodeGenPrepare] Freeze condition when transforming select to br
Juneyoung Lee via llvm-commits
llvm-commits at lists.llvm.org
Sun Mar 15 20:30:43 PDT 2020
oops, I'll be careful next time
On Mon, Mar 16, 2020 at 12:15 PM Philip Reames via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> minor: past tense of freeze is frozen, not freezed.
>
> On 3/14/20 7:10 PM, Juneyoung Lee via llvm-commits wrote:
> > Author: Juneyoung Lee
> > Date: 2020-03-15T11:10:46+09:00
> > New Revision: 10aa7ea951e22dbd7f2ebdeb6410cfbc8a251eb1
> >
> > URL:
> https://github.com/llvm/llvm-project/commit/10aa7ea951e22dbd7f2ebdeb6410cfbc8a251eb1
> > DIFF:
> https://github.com/llvm/llvm-project/commit/10aa7ea951e22dbd7f2ebdeb6410cfbc8a251eb1.diff
> >
> > LOG: [CodeGenPrepare] Freeze condition when transforming select to br
> >
> > Summary:
> > This is a simple fix for CodeGenPrepare that freezes branch condition
> when transforming select to branch.
> > If it is not freezed, instsimplify or the later pipeline can potentially
> exploit undefined behavior.
> >
> > The diff shows optimized form becase D75859 and D76048 already made a
> few changes to CodeGenPrepare for optimizing freeze(cmp).
> >
> > Reviewers: jdoerfert, spatel, lebedev.ri, efriedma
> >
> > Reviewed By: lebedev.ri
> >
> > Subscribers: hiraditya, llvm-commits
> >
> > Tags: #llvm
> >
> > Differential Revision: https://reviews.llvm.org/D76179
> >
> > Added:
> >
> >
> > Modified:
> > llvm/lib/CodeGen/CodeGenPrepare.cpp
> > llvm/test/CodeGen/ARM/2012-08-30-select.ll
> > llvm/test/Transforms/CodeGenPrepare/X86/optimizeSelect-DT.ll
> > llvm/test/Transforms/CodeGenPrepare/X86/select.ll
> >
> > Removed:
> >
> >
> >
> >
> ################################################################################
> > diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp
> b/llvm/lib/CodeGen/CodeGenPrepare.cpp
> > index 373064da7bb8..fd55ef2936b0 100644
> > --- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
> > +++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
> > @@ -6131,7 +6131,8 @@ bool CodeGenPrepare::optimizeSelectInst(SelectInst
> *SI) {
> > // Into:
> > // start:
> > // %cmp = cmp uge i32 %a, %b
> > - // br i1 %cmp, label %select.true, label %select.false
> > + // %cmp.frozen = freeze %cmp
> > + // br i1 %cmp.frozen, label %select.true, label %select.false
> > // select.true:
> > // br label %select.end
> > // select.false:
> > @@ -6139,6 +6140,7 @@ bool CodeGenPrepare::optimizeSelectInst(SelectInst
> *SI) {
> > // select.end:
> > // %sel = phi i32 [ %c, %select.true ], [ %d, %select.false ]
> > //
> > + // %cmp should be freezed, otherwise it may introduce undefined
> behavior.
> > // In addition, we may sink instructions that produce %c or %d from
> > // the entry block into the destination(s) of the new branch.
> > // If the true or false blocks do not contain a sunken instruction,
> that
> > @@ -6217,7 +6219,9 @@ bool CodeGenPrepare::optimizeSelectInst(SelectInst
> *SI) {
> > TT = TrueBlock;
> > FT = FalseBlock;
> > }
> > - IRBuilder<>(SI).CreateCondBr(SI->getCondition(), TT, FT, SI);
> > + IRBuilder<> IB(SI);
> > + auto CondFr = IB.CreateFreeze(SI->getCondition(), SI->getName() +
> ".frozen");
> > + IB.CreateCondBr(CondFr, TT, FT, SI);
> >
> > SmallPtrSet<const Instruction *, 2> INS;
> > INS.insert(ASI.begin(), ASI.end());
> >
> > diff --git a/llvm/test/CodeGen/ARM/2012-08-30-select.ll
> b/llvm/test/CodeGen/ARM/2012-08-30-select.ll
> > index 97b732beb4d7..b51688702a54 100644
> > --- a/llvm/test/CodeGen/ARM/2012-08-30-select.ll
> > +++ b/llvm/test/CodeGen/ARM/2012-08-30-select.ll
> > @@ -2,9 +2,9 @@
> > ; rdar://12201387
> >
> > ;CHECK-LABEL: select_s_v_v:
> > +;CHECK: vmov.i32
> > ;CHECK: vmov
> > ;CHECK-NEXT: vmov
> > -;CHECK: vmov.i32
> > ;CHECK: bx
> > define <16 x i8> @select_s_v_v(<16 x i8> %vec, i32 %avail) {
> > entry:
> >
> > diff --git
> a/llvm/test/Transforms/CodeGenPrepare/X86/optimizeSelect-DT.ll
> b/llvm/test/Transforms/CodeGenPrepare/X86/optimizeSelect-DT.ll
> > index 05389bfe8d0a..eb4e4ce431af 100644
> > --- a/llvm/test/Transforms/CodeGenPrepare/X86/optimizeSelect-DT.ll
> > +++ b/llvm/test/Transforms/CodeGenPrepare/X86/optimizeSelect-DT.ll
> > @@ -7,7 +7,8 @@ target triple = "x86_64-unknown-linux-gnu"
> > define i1 @PR41004(i32 %x, i32 %y, i32 %t1) {
> > ; CHECK-LABEL: @PR41004(
> > ; CHECK-NEXT: entry:
> > -; CHECK-NEXT: [[T0:%.*]] = icmp eq i32 [[Y:%.*]], 1
> > +; CHECK-NEXT: [[MUL_FR:%.*]] = freeze i32 [[Y:%.*]]
> > +; CHECK-NEXT: [[T0:%.*]] = icmp eq i32 [[MUL_FR]], 1
> > ; CHECK-NEXT: br i1 [[T0]], label [[SELECT_TRUE_SINK:%.*]], label
> [[SELECT_END:%.*]]
> > ; CHECK: select.true.sink:
> > ; CHECK-NEXT: [[REM:%.*]] = srem i32 [[X:%.*]], 2
> >
> > diff --git a/llvm/test/Transforms/CodeGenPrepare/X86/select.ll
> b/llvm/test/Transforms/CodeGenPrepare/X86/select.ll
> > index 7829376e9db1..390794ab3cda 100644
> > --- a/llvm/test/Transforms/CodeGenPrepare/X86/select.ll
> > +++ b/llvm/test/Transforms/CodeGenPrepare/X86/select.ll
> > @@ -27,7 +27,8 @@ entry:
> > define float @fdiv_true_sink(float %a, float %b) {
> > ; CHECK-LABEL: @fdiv_true_sink(
> > ; CHECK-NEXT: entry:
> > -; CHECK-NEXT: [[CMP:%.*]] = fcmp ogt float [[A:%.*]], 1.000000e+00
> > +; CHECK-NEXT: [[SEL_FR:%.*]] = freeze float [[A:%.*]]
> > +; CHECK-NEXT: [[CMP:%.*]] = fcmp ogt float [[SEL_FR]], 1.000000e+00
> > ; CHECK-NEXT: br i1 [[CMP]], label [[SELECT_TRUE_SINK:%.*]], label
> [[SELECT_END:%.*]]
> > ; CHECK: select.true.sink:
> > ; CHECK-NEXT: [[DIV:%.*]] = fdiv float [[A]], [[B:%.*]]
> > @@ -38,7 +39,8 @@ define float @fdiv_true_sink(float %a, float %b) {
> > ;
> > ; DEBUG-LABEL: @fdiv_true_sink(
> > ; DEBUG-NEXT: entry:
> > -; DEBUG-NEXT: [[CMP:%.*]] = fcmp ogt float [[A:%.*]], 1.000000e+00
> > +; DEBUG-NEXT: [[SEL_FR:%.*]] = freeze float [[A:%.*]]
> > +; DEBUG-NEXT: [[CMP:%.*]] = fcmp ogt float [[SEL_FR]], 1.000000e+00,
> !dbg !24
> > ; DEBUG-NEXT: call void @llvm.dbg.value(metadata i1 [[CMP]]
> > ; DEBUG-NEXT: br i1 [[CMP]], label [[SELECT_TRUE_SINK:%.*]], label
> [[SELECT_END:%.*]], !dbg
> > ; DEBUG: select.true.sink:
> > @@ -60,7 +62,8 @@ entry:
> > define float @fdiv_false_sink(float %a, float %b) {
> > ; CHECK-LABEL: @fdiv_false_sink(
> > ; CHECK-NEXT: entry:
> > -; CHECK-NEXT: [[CMP:%.*]] = fcmp ogt float [[A:%.*]], 3.000000e+00
> > +; CHECK-NEXT: [[SEL_FR:%.*]] = freeze float [[A:%.*]]
> > +; CHECK-NEXT: [[CMP:%.*]] = fcmp ogt float [[SEL_FR]], 3.000000e+00
> > ; CHECK-NEXT: br i1 [[CMP]], label [[SELECT_END:%.*]], label
> [[SELECT_FALSE_SINK:%.*]]
> > ; CHECK: select.false.sink:
> > ; CHECK-NEXT: [[DIV:%.*]] = fdiv float [[A]], [[B:%.*]]
> > @@ -71,7 +74,8 @@ define float @fdiv_false_sink(float %a, float %b) {
> > ;
> > ; DEBUG-LABEL: @fdiv_false_sink(
> > ; DEBUG-NEXT: entry:
> > -; DEBUG-NEXT: [[CMP:%.*]] = fcmp ogt float [[A:%.*]], 3.000000e+00
> > +; DEBUG-NEXT: [[SEL_FR:%.*]] = freeze float [[A:%.*]]
> > +; DEBUG-NEXT: [[CMP:%.*]] = fcmp ogt float [[SEL_FR]], 3.000000e+00,
> !dbg !33
> > ; DEBUG-NEXT: call void @llvm.dbg.value(metadata i1 [[CMP]]
> > ; DEBUG-NEXT: br i1 [[CMP]], label [[SELECT_END:%.*]], label
> [[SELECT_FALSE_SINK:%.*]], !dbg
> > ; DEBUG: select.false.sink:
> > @@ -93,7 +97,8 @@ entry:
> > define float @fdiv_both_sink(float %a, float %b) {
> > ; CHECK-LABEL: @fdiv_both_sink(
> > ; CHECK-NEXT: entry:
> > -; CHECK-NEXT: [[CMP:%.*]] = fcmp ogt float [[A:%.*]], 5.000000e+00
> > +; CHECK-NEXT: [[SEL_FR:%.*]] = freeze float [[A:%.*]]
> > +; CHECK-NEXT: [[CMP:%.*]] = fcmp ogt float [[SEL_FR]], 5.000000e+00
> > ; CHECK-NEXT: br i1 [[CMP]], label [[SELECT_TRUE_SINK:%.*]], label
> [[SELECT_FALSE_SINK:%.*]]
> > ; CHECK: select.true.sink:
> > ; CHECK-NEXT: [[DIV1:%.*]] = fdiv float [[A]], [[B:%.*]]
> >
> >
> >
> > _______________________________________________
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> > llvm-commits at lists.llvm.org
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--
Juneyoung Lee
Software Foundation Lab, Seoul National University
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