a2ca902033
Summary: This patch teaches SCEV to calculate the maxBECount when the end bound of the loop can vary. Note that we cannot calculate the exactBECount. This will only be done when both conditions are satisfied: 1. the loop termination condition is strictly LT. 2. the IV is proven to not overflow. This provides more information to users of SCEV and can be used to improve identification of finite loops. Reviewers: sanjoy, mkazantsev, silviu.baranga, atrick Reviewed by: mkazantsev Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D38825 llvm-svn: 315683
181 lines
7.5 KiB
LLVM
181 lines
7.5 KiB
LLVM
; RUN: opt -S < %s -analyze -scalar-evolution -loop-simplify -scalar-evolution | FileCheck %s
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; Provide legal integer types.
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target datalayout = "n8:16:32:64"
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@maxStat = external global i32
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; LoopSimplify should invalidate SCEV when splitting out the
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; inner loop.
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;
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; First SCEV print:
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; CHECK-LABEL: Classifying expressions for: @test
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; CHECK: %[[PHI:.*]] = phi i32 [ 0, %entry ], [ %{{.*}}, %if.then5 ], [ %[[PHI]], %if.end ]
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; CHECK-LABEL: Determining loop execution counts for: @test
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; CHECK: Loop %for.body18: Unpredictable backedge-taken count.
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; CHECK: Loop %for.body18: max backedge-taken count is 2147483646
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; CHECK: Loop %for.body18: Unpredictable predicated backedge-taken count.
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; CHECK: Loop %for.cond: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %for.cond: Unpredictable max backedge-taken count.
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; CHECK: Loop %for.cond: Unpredictable predicated backedge-taken count.
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;
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; Now simplify the loop, which should cause SCEV to re-compute more precise
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; info here in addition to having preheader PHIs. Second SCEV print:
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; CHECK-LABEL: Classifying expressions for: @test
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; CHECK: phi i32 [ %{{.*}}, %if.then5 ], [ 0, %entry ]
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; CHECK-LABEL: Determining loop execution counts for: @test
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; CHECK: Loop %for.body18: Unpredictable backedge-taken count.
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; CHECK: Loop %for.body18: max backedge-taken count is 2147483646
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; CHECK: Loop %for.body18: Unpredictable predicated backedge-taken count.
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; CHECK: Loop %for.cond: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %for.cond: max backedge-taken count is -2147483647
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; CHECK: Loop %for.cond: Unpredictable predicated backedge-taken count.
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; CHECK: Loop %for.cond.outer: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %for.cond.outer: Unpredictable max backedge-taken count.
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; CHECK: Loop %for.cond.outer: Unpredictable predicated backedge-taken count.
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define i32 @test() nounwind {
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entry:
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br label %for.cond
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for.cond: ; preds = %if.then5, %if.end, %entry
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%cuts.1 = phi i32 [ 0, %entry ], [ %inc, %if.then5 ], [ %cuts.1, %if.end ]
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%0 = phi i32 [ 0, %entry ], [ %add, %if.end ], [ %add, %if.then5 ]
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%add = add i32 %0, 1
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%cmp = icmp slt i32 %0, 1
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%tmp1 = load i32, i32* @maxStat, align 4
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br i1 %cmp, label %for.body, label %for.cond14.preheader
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for.cond14.preheader: ; preds = %for.cond
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%cmp1726 = icmp sgt i32 %tmp1, 0
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br i1 %cmp1726, label %for.body18, label %return
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for.body: ; preds = %for.cond
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%cmp2 = icmp sgt i32 %tmp1, 100
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br i1 %cmp2, label %return, label %if.end
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if.end: ; preds = %for.body
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%cmp4 = icmp sgt i32 %tmp1, -1
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br i1 %cmp4, label %if.then5, label %for.cond
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if.then5: ; preds = %if.end
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call void @foo() nounwind
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%inc = add i32 %cuts.1, 1
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br label %for.cond
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for.body18: ; preds = %for.body18, %for.cond14.preheader
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%i13.027 = phi i32 [ %1, %for.body18 ], [ 0, %for.cond14.preheader ]
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call void @foo() nounwind
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%1 = add nsw i32 %i13.027, 1
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%tmp16 = load i32, i32* @maxStat, align 4
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%cmp17 = icmp slt i32 %1, %tmp16
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br i1 %cmp17, label %for.body18, label %return
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return: ; preds = %for.body18, %for.body, %for.cond14.preheader
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ret i32 0
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}
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declare void @foo() nounwind
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; Notify SCEV when removing an ExitingBlock. This only changes the
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; backedge-taken information.
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;
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; First SCEV print:
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; CHECK-LABEL: Determining loop execution counts for: @mergeExit
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; CHECK: Loop %while.cond191: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %while.cond191: max backedge-taken count is -1
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; CHECK: Loop %while.cond191: Unpredictable predicated backedge-taken count.
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; CHECK: Loop %while.cond191.outer: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %while.cond191.outer: Unpredictable max backedge-taken count.
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; CHECK: Loop %while.cond191.outer: Unpredictable predicated backedge-taken count.
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;
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; After simplifying, the max backedge count is refined.
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; Second SCEV print:
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; CHECK-LABEL: Determining loop execution counts for: @mergeExit
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; CHECK: Loop %while.cond191: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %while.cond191: max backedge-taken count is 0
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; CHECK: Loop %while.cond191: Unpredictable predicated backedge-taken count.
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; CHECK: Loop %while.cond191.outer: <multiple exits> Unpredictable backedge-taken count.
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; CHECK: Loop %while.cond191.outer: Unpredictable max backedge-taken count.
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; CHECK: Loop %while.cond191.outer: Unpredictable predicated backedge-taken count.
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define void @mergeExit(i32 %MapAttrCount) nounwind uwtable ssp {
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entry:
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br i1 undef, label %if.then124, label %if.end126
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if.then124: ; preds = %entry
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unreachable
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if.end126: ; preds = %entry
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br i1 undef, label %while.body.lr.ph, label %if.end591
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while.body.lr.ph: ; preds = %if.end126
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br i1 undef, label %if.end140, label %if.then137
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if.then137: ; preds = %while.body.lr.ph
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unreachable
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if.end140: ; preds = %while.body.lr.ph
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br i1 undef, label %while.cond191.outer, label %if.then148
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if.then148: ; preds = %if.end140
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unreachable
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while.cond191.outer: ; preds = %if.then205, %if.end140
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br label %while.cond191
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while.cond191: ; preds = %while.body197, %while.cond191.outer
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%CppIndex.0 = phi i32 [ %inc, %while.body197 ], [ undef, %while.cond191.outer ]
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br i1 undef, label %land.rhs, label %if.then216
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land.rhs: ; preds = %while.cond191
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%inc = add i32 %CppIndex.0, 1
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%cmp196 = icmp ult i32 %inc, %MapAttrCount
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br i1 %cmp196, label %while.body197, label %if.then216
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while.body197: ; preds = %land.rhs
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br i1 undef, label %if.then205, label %while.cond191
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if.then205: ; preds = %while.body197
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br label %while.cond191.outer
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if.then216: ; preds = %land.rhs, %while.cond191
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br i1 undef, label %if.else, label %if.then221
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if.then221: ; preds = %if.then216
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unreachable
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if.else: ; preds = %if.then216
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br i1 undef, label %if.then266, label %if.end340
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if.then266: ; preds = %if.else
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switch i32 undef, label %if.else329 [
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i32 17, label %if.then285
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i32 19, label %if.then285
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i32 18, label %if.then285
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i32 15, label %if.then285
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]
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if.then285: ; preds = %if.then266, %if.then266, %if.then266, %if.then266
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br i1 undef, label %if.then317, label %if.else324
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if.then317: ; preds = %if.then285
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br label %if.end340
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if.else324: ; preds = %if.then285
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unreachable
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if.else329: ; preds = %if.then266
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unreachable
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if.end340: ; preds = %if.then317, %if.else
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unreachable
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if.end591: ; preds = %if.end126
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br i1 undef, label %cond.end, label %cond.false
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cond.false: ; preds = %if.end591
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unreachable
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cond.end: ; preds = %if.end591
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ret void
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}
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