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Teach ScalarEvolution how to analyze loops with multiple exit

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blocks, and also exit blocks with multiple conditions (combined
with (bitwise) ands and ors). It's often infeasible to compute an
exact trip count in such cases, but a useful upper bound can often
be found.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73866 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-06-22 00:31:57 +00:00
parent 743ab498d8
commit a334aa7a10
3 changed files with 300 additions and 27 deletions
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48
test/Analysis/ScalarEvolution/trip-count5.ll Normal file
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; RUN: llvm-as < %s | opt -analyze -scalar-evolution -disable-output > %t
; RUN: grep sext %t | count 2
; RUN: not grep {(sext} %t
; ScalarEvolution should be able to compute a maximum trip count
; value sufficient to fold away both sext casts.
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
define float @t(float* %pTmp1, float* %peakWeight, float* %nrgReducePeakrate, i32 %bim) nounwind {
entry:
%tmp3 = load float* %peakWeight, align 4 ; <float> [#uses=2]
%tmp2538 = icmp sgt i32 %bim, 0 ; <i1> [#uses=1]
br i1 %tmp2538, label %bb.nph, label %bb4
bb.nph: ; preds = %entry
br label %bb
bb: ; preds = %bb1, %bb.nph
%distERBhi.036 = phi float [ %tmp10, %bb1 ], [ 0.000000e+00, %bb.nph ] ; <float> [#uses=1]
%hiPart.035 = phi i32 [ %tmp12, %bb1 ], [ 0, %bb.nph ] ; <i32> [#uses=2]
%peakCount.034 = phi float [ %tmp19, %bb1 ], [ %tmp3, %bb.nph ] ; <float> [#uses=1]
%tmp6 = sext i32 %hiPart.035 to i64 ; <i64> [#uses=1]
%tmp7 = getelementptr float* %pTmp1, i64 %tmp6 ; <float*> [#uses=1]
%tmp8 = load float* %tmp7, align 4 ; <float> [#uses=1]
%tmp10 = fadd float %tmp8, %distERBhi.036 ; <float> [#uses=3]
%tmp12 = add i32 %hiPart.035, 1 ; <i32> [#uses=3]
%tmp15 = sext i32 %tmp12 to i64 ; <i64> [#uses=1]
%tmp16 = getelementptr float* %peakWeight, i64 %tmp15 ; <float*> [#uses=1]
%tmp17 = load float* %tmp16, align 4 ; <float> [#uses=1]
%tmp19 = fadd float %tmp17, %peakCount.034 ; <float> [#uses=2]
br label %bb1
bb1: ; preds = %bb
%tmp21 = fcmp olt float %tmp10, 2.500000e+00 ; <i1> [#uses=1]
%tmp25 = icmp slt i32 %tmp12, %bim ; <i1> [#uses=1]
%tmp27 = and i1 %tmp21, %tmp25 ; <i1> [#uses=1]
br i1 %tmp27, label %bb, label %bb1.bb4_crit_edge
bb1.bb4_crit_edge: ; preds = %bb1
br label %bb4
bb4: ; preds = %bb1.bb4_crit_edge, %entry
%distERBhi.0.lcssa = phi float [ %tmp10, %bb1.bb4_crit_edge ], [ 0.000000e+00, %entry ] ; <float> [#uses=1]
%peakCount.0.lcssa = phi float [ %tmp19, %bb1.bb4_crit_edge ], [ %tmp3, %entry ] ; <float> [#uses=1]
%tmp31 = fdiv float %peakCount.0.lcssa, %distERBhi.0.lcssa ; <float> [#uses=1]
ret float %tmp31
}