diff --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp index 07b201bdf182..e8e6cf21f1c4 100644 --- a/llvm/lib/CodeGen/RegAllocGreedy.cpp +++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp @@ -125,6 +125,11 @@ static cl::opt EnableDeferredSpilling( "variable because of other evicted variables."), cl::init(false)); +static cl::opt + HugeSizeForSplit("huge-size-for-split", cl::Hidden, + cl::desc("Last chance recoloring max depth"), + cl::init(5000)); + // FIXME: Find a good default for this flag and remove the flag. static cl::opt CSRFirstTimeCost("regalloc-csr-first-time-cost", @@ -478,6 +483,7 @@ private: SmallVectorImpl&, unsigned = ~0u); unsigned tryRegionSplit(LiveInterval&, AllocationOrder&, SmallVectorImpl&); + unsigned isSplitBenefitWorthCost(LiveInterval &VirtReg); /// Calculate cost of region splitting. unsigned calculateRegionSplitCost(LiveInterval &VirtReg, AllocationOrder &Order, @@ -1771,8 +1777,21 @@ void RAGreedy::splitAroundRegion(LiveRangeEdit &LREdit, MF->verify(this, "After splitting live range around region"); } +// Global split has high compile time cost especially for large live range. +// Return false for the case here where the potential benefit will never +// worth the cost. +unsigned RAGreedy::isSplitBenefitWorthCost(LiveInterval &VirtReg) { + MachineInstr *MI = MRI->getUniqueVRegDef(VirtReg.reg); + if (MI && TII->isTriviallyReMaterializable(*MI, AA) && + VirtReg.size() > HugeSizeForSplit) + return false; + return true; +} + unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order, SmallVectorImpl &NewVRegs) { + if (!isSplitBenefitWorthCost(VirtReg)) + return 0; unsigned NumCands = 0; BlockFrequency SpillCost = calcSpillCost(); BlockFrequency BestCost; diff --git a/llvm/test/CodeGen/X86/limit-split-cost.mir b/llvm/test/CodeGen/X86/limit-split-cost.mir new file mode 100644 index 000000000000..219ff3741a7c --- /dev/null +++ b/llvm/test/CodeGen/X86/limit-split-cost.mir @@ -0,0 +1,150 @@ +# REQUIRES: asserts +# RUN: llc -mtriple=x86_64-- -run-pass=greedy %s -debug-only=regalloc -huge-size-for-split=0 -o /dev/null 2>&1 | FileCheck %s +# Check no global region split is needed because the live range to split is trivially rematerializable. +# CHECK-NOT: Compact region bundles +--- | + ; ModuleID = '' + source_filename = "2.cc" + target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" + target triple = "x86_64-unknown-linux-gnu" + + @m = local_unnamed_addr global i32 0, align 4 + @.str = private unnamed_addr constant [4 x i8] c"abc\00", align 1 + @.str.1 = private unnamed_addr constant [4 x i8] c"def\00", align 1 + @.str.2 = private unnamed_addr constant [4 x i8] c"ghi\00", align 1 + + ; Function Attrs: uwtable + define void @_Z3fooi(i32 %value) local_unnamed_addr #0 { + entry: + br label %do.body + + do.body: ; preds = %do.cond, %entry + tail call void asm sideeffect "", "~{r10},~{r11},~{r12},~{r13},~{r14},~{r15},~{dirflag},~{fpsr},~{flags}"() #2, !srcloc !3 + switch i32 %value, label %do.cond [ + i32 0, label %sw.bb + i32 1, label %sw.bb1 + i32 2, label %sw.bb2 + ] + + sw.bb: ; preds = %do.body + tail call void @_Z3gooPKc(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i64 0, i64 0)) + br label %sw.bb1 + + sw.bb1: ; preds = %sw.bb, %do.body + tail call void @_Z3gooPKc(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0)) + br label %sw.bb2 + + sw.bb2: ; preds = %sw.bb1, %do.body + tail call void @_Z3gooPKc(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.2, i64 0, i64 0)) + br label %do.cond + + do.cond: ; preds = %sw.bb2, %do.body + %0 = load i32, i32* @m, align 4, !tbaa !4 + %cmp = icmp eq i32 %0, 5 + br i1 %cmp, label %do.end, label %do.body + + do.end: ; preds = %do.cond + ret void + } + + declare void @_Z3gooPKc(i8*) local_unnamed_addr #1 + + ; Function Attrs: nounwind + declare void @llvm.stackprotector(i8*, i8**) #2 + + attributes #0 = { uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" } + attributes #1 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" } + attributes #2 = { nounwind } + + !llvm.module.flags = !{!0, !1} + !llvm.ident = !{!2} + + !0 = !{i32 1, !"wchar_size", i32 4} + !1 = !{i32 7, !"PIC Level", i32 2} + !2 = !{!"clang version 7.0.0 (trunk 335057)"} + !3 = !{i32 80} + !4 = !{!5, !5, i64 0} + !5 = !{!"int", !6, i64 0} + !6 = !{!"omnipotent char", !7, i64 0} + !7 = !{!"Simple C++ TBAA"} + +... +--- +name: _Z3fooi +alignment: 4 +tracksRegLiveness: true +registers: + - { id: 0, class: gr32 } + - { id: 1, class: gr32 } + - { id: 2, class: gr32 } + - { id: 3, class: gr64 } + - { id: 4, class: gr64 } + - { id: 5, class: gr64 } + - { id: 6, class: gr64 } + - { id: 7, class: gr32 } + - { id: 8, class: gr32 } +liveins: + - { reg: '$edi', virtual-reg: '%0' } +frameInfo: + hasCalls: true +body: | + bb.0.entry: + liveins: $edi + + %0:gr32 = COPY $edi + %5:gr64 = LEA64r $rip, 1, $noreg, @.str.2, $noreg + %6:gr64 = MOV64rm $rip, 1, $noreg, target-flags(x86-gotpcrel) @m, $noreg :: (load 8 from got) + %4:gr64 = LEA64r $rip, 1, $noreg, @.str.1, $noreg + %3:gr64 = LEA64r $rip, 1, $noreg, @.str, $noreg + + bb.1.do.body: + successors: %bb.6(0x20000000), %bb.2(0x60000000) + + INLINEASM &"", 1, 12, implicit-def dead early-clobber $r10, 12, implicit-def dead early-clobber $r11, 12, implicit-def dead early-clobber $r12, 12, implicit-def dead early-clobber $r13, 12, implicit-def dead early-clobber $r14, 12, implicit-def dead early-clobber $r15, 12, implicit-def dead early-clobber $eflags, !3 + CMP32ri8 %0, 2, implicit-def $eflags + JE_1 %bb.6, implicit killed $eflags + JMP_1 %bb.2 + + bb.2.do.body: + successors: %bb.5(0x2aaaaaab), %bb.3(0x55555555) + + CMP32ri8 %0, 1, implicit-def $eflags + JE_1 %bb.5, implicit killed $eflags + JMP_1 %bb.3 + + bb.3.do.body: + successors: %bb.4, %bb.7 + + TEST32rr %0, %0, implicit-def $eflags + JNE_1 %bb.7, implicit killed $eflags + JMP_1 %bb.4 + + bb.4.sw.bb: + ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp + $rdi = COPY %3 + CALL64pcrel32 target-flags(x86-plt) @_Z3gooPKc, csr_64, implicit $rsp, implicit $ssp, implicit $rdi, implicit-def $rsp, implicit-def $ssp + ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp + + bb.5.sw.bb1: + ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp + $rdi = COPY %4 + CALL64pcrel32 target-flags(x86-plt) @_Z3gooPKc, csr_64, implicit $rsp, implicit $ssp, implicit $rdi, implicit-def $rsp, implicit-def $ssp + ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp + + bb.6.sw.bb2: + ADJCALLSTACKDOWN64 0, 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp + $rdi = COPY %5 + CALL64pcrel32 target-flags(x86-plt) @_Z3gooPKc, csr_64, implicit $rsp, implicit $ssp, implicit $rdi, implicit-def $rsp, implicit-def $ssp + ADJCALLSTACKUP64 0, 0, implicit-def dead $rsp, implicit-def dead $eflags, implicit-def dead $ssp, implicit $rsp, implicit $ssp + + bb.7.do.cond: + successors: %bb.8(0x04000000), %bb.1(0x7c000000) + + CMP32mi8 %6, 1, $noreg, 0, $noreg, 5, implicit-def $eflags :: (dereferenceable load 4 from @m, !tbaa !4) + JNE_1 %bb.1, implicit killed $eflags + JMP_1 %bb.8 + + bb.8.do.end: + RET 0 + +...