llvm-6502/test/Transforms/StructurizeCFG/post-order-traversal-bug.ll
Tom Stellard 7c038bc15f StructurizeCFG: Use a reverse post-order traversal
We were previously doing a post-order traversal and operating on the
list in reverse, however this would occasionaly cause backedges for
loops to be visited before some of the other blocks in the loop.

We know use a reverse post-order traversal, which avoids this issue.

The reverse post-order traversal is not completely ideal, so we need
to manually fixup the list to ensure that inner loop backedges are
visited before outer loop backedges.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228186 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-04 20:49:44 +00:00

101 lines
4.1 KiB
LLVM

; RUN: opt -S -structurizecfg %s -o - | FileCheck %s
; The structurize cfg pass used to do a post-order traversal to generate a list
; of ; basic blocks and then operate on the list in reverse. This led to bugs,
; because sometimes successors would be visited before their predecessors.
; The fix for this was to do a reverse post-order traversal which is what the
; algorithm requires.
; Function Attrs: nounwind
define void @test(float* nocapture %out, i32 %K1, float* nocapture readonly %nr) {
; CHECK: entry:
; CHECK: br label %for.body
entry:
br label %for.body
; CHECK: for.body:
; CHECK: br i1 %{{[0-9]+}}, label %lor.lhs.false, label %Flow
for.body: ; preds = %for.body.backedge, %entry
%indvars.iv = phi i64 [ %indvars.iv.be, %for.body.backedge ], [ 1, %entry ]
%best_val.027 = phi float [ %best_val.027.be, %for.body.backedge ], [ 5.000000e+01, %entry ]
%prev_start.026 = phi i32 [ %tmp26, %for.body.backedge ], [ 0, %entry ]
%best_count.025 = phi i32 [ %best_count.025.be, %for.body.backedge ], [ 0, %entry ]
%tmp0 = trunc i64 %indvars.iv to i32
%cmp1 = icmp eq i32 %tmp0, %K1
br i1 %cmp1, label %if.then, label %lor.lhs.false
; CHECK: lor.lhs.false:
; CHECK: br label %Flow
lor.lhs.false: ; preds = %for.body
%arrayidx = getelementptr inbounds float* %nr, i64 %indvars.iv
%tmp1 = load float* %arrayidx, align 4
%tmp2 = add nsw i64 %indvars.iv, -1
%arrayidx2 = getelementptr inbounds float* %nr, i64 %tmp2
%tmp3 = load float* %arrayidx2, align 4
%cmp3 = fcmp une float %tmp1, %tmp3
br i1 %cmp3, label %if.then, label %for.body.1
; CHECK: Flow:
; CHECK: br i1 %{{[0-9]+}}, label %if.then, label %Flow1
; CHECK: if.then:
; CHECK: br label %Flow1
if.then: ; preds = %lor.lhs.false, %for.body
%sub4 = sub nsw i32 %tmp0, %prev_start.026
%tmp4 = add nsw i64 %indvars.iv, -1
%arrayidx8 = getelementptr inbounds float* %nr, i64 %tmp4
%tmp5 = load float* %arrayidx8, align 4
br i1 %cmp1, label %for.end, label %for.body.1
; CHECK: for.end:
; CHECK: ret void
for.end: ; preds = %for.body.1, %if.then
%best_val.0.lcssa = phi float [ %best_val.233, %for.body.1 ], [ %tmp5, %if.then ]
store float %best_val.0.lcssa, float* %out, align 4
ret void
; CHECK: Flow1
; CHECK: br i1 %{{[0-9]}}, label %for.body.1, label %Flow2
; CHECK: for.body.1:
; CHECK: br i1 %{{[0-9]+}}, label %for.body.6, label %Flow3
for.body.1: ; preds = %if.then, %lor.lhs.false
%best_val.233 = phi float [ %tmp5, %if.then ], [ %best_val.027, %lor.lhs.false ]
%best_count.231 = phi i32 [ %sub4, %if.then ], [ %best_count.025, %lor.lhs.false ]
%indvars.iv.next.454 = add nsw i64 %indvars.iv, 5
%tmp22 = trunc i64 %indvars.iv.next.454 to i32
%cmp1.5 = icmp eq i32 %tmp22, %K1
br i1 %cmp1.5, label %for.end, label %for.body.6
; CHECK: Flow2:
; CHECK: br i1 %{{[0-9]+}}, label %for.end, label %for.body
; CHECK: for.body.6:
; CHECK: br i1 %cmp5.6, label %if.then6.6, label %for.body.backedge
for.body.6: ; preds = %for.body.1
%indvars.iv.next.559 = add nsw i64 %indvars.iv, 6
%tmp26 = trunc i64 %indvars.iv.next.559 to i32
%sub4.6 = sub nsw i32 %tmp26, %tmp22
%cmp5.6 = icmp slt i32 %best_count.231, %sub4.6
br i1 %cmp5.6, label %if.then6.6, label %for.body.backedge
; CHECK: if.then6.6
; CHECK: br label %for.body.backedge
if.then6.6: ; preds = %for.body.6
%arrayidx8.6 = getelementptr inbounds float* %nr, i64 %indvars.iv.next.454
%tmp29 = load float* %arrayidx8.6, align 4
br label %for.body.backedge
; CHECK: Flow3:
; CHECK: br label %Flow2
; CHECK: for.body.backedge:
; CHECK: br label %Flow3
for.body.backedge: ; preds = %if.then6.6, %for.body.6
%best_val.027.be = phi float [ %tmp29, %if.then6.6 ], [ %best_val.233, %for.body.6 ]
%best_count.025.be = phi i32 [ %sub4.6, %if.then6.6 ], [ %best_count.231, %for.body.6 ]
%indvars.iv.be = add nsw i64 %indvars.iv, 7
br label %for.body
}