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https://github.com/RPCS3/llvm-mirror.git
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58953554d4
Summary: When simplifying unconditional branches from empty blocks, we pre-test if the BB belongs to a set of loop headers and keep the block to prevent passes from destroying canonical loop structure. However, the current algorithm fails if the destination of the branch is a loop header. Especially when such a loop's latch block is folded into loop header it results in additional backedges and LoopSimplify turns it into a nested loop which prevent later optimizations from being applied (e.g., loop unrolling and loop interleaving). This patch augments the existing algorithm by further checking if the destination of the branch belongs to a set of loop headers and defer eliminating it if yes to LateSimplifyCFG. Fixes PR33605: https://bugs.llvm.org/show_bug.cgi?id=33605 Reviewers: efriedma, mcrosier, pacxx, hsung, davidxl Reviewed By: efriedma Subscribers: ashutosh.nema, gberry, javed.absar, llvm-commits Differential Revision: https://reviews.llvm.org/D35411 llvm-svn: 308422
78 lines
3.0 KiB
LLVM
78 lines
3.0 KiB
LLVM
;RUN: opt -loop-unswitch -simplifycfg -S < %s | FileCheck %s
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define i32 @foo(i32 %a, i32 %b) {
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;CHECK-LABEL: foo
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entry:
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br label %for.body.lr.ph
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for.body.lr.ph: ; preds = %entry
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%cmp0 = icmp sgt i32 %b, 0
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br i1 %cmp0, label %for.body, label %for.cond.cleanup
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for.body: ; preds = %for.inc, %for.body.lr.ph
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%inc.i = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.inc ]
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%mul.i = phi i32 [ 3, %for.body.lr.ph ], [ %mul.p, %for.inc ]
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%add.i = phi i32 [ %a, %for.body.lr.ph ], [ %add.p, %for.inc ]
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%cmp1 = icmp eq i32 %a, 12345
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br i1 %cmp1, label %if.then, label %if.else, !prof !0
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; CHECK: %cmp1 = icmp eq i32 %a, 12345
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; CHECK-NEXT: br i1 %cmp1, label %for.body.preheader.split.us, label %for.body.preheader.split, !prof !0
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if.then: ; preds = %for.body
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; CHECK: for.body.us:
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; CHECK: add nsw i32 %{{.*}}, 123
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; CHECK: %exitcond.us = icmp eq i32 %inc.us, %b
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; CHECK: br i1 %exitcond.us, label %for.cond.cleanup, label %for.body.us
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%add = add nsw i32 %add.i, 123
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br label %for.inc
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if.else: ; preds = %for.body
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%mul = mul nsw i32 %mul.i, %b
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br label %for.inc
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; CHECK: for.body:
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; CHECK: %mul = mul nsw i32 %mul.i, %b
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; CHECK: %inc = add nuw nsw i32 %inc.i, 1
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; CHECK: %exitcond = icmp eq i32 %inc, %b
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; CHECK: br i1 %exitcond, label %for.cond.cleanup, label %for.body
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for.inc: ; preds = %if.then, %if.else
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%mul.p = phi i32 [ %b, %if.then ], [ %mul, %if.else ]
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%add.p = phi i32 [ %add, %if.then ], [ %a, %if.else ]
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%inc = add nuw nsw i32 %inc.i, 1
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%exitcond = icmp eq i32 %inc, %b
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br i1 %exitcond, label %for.cond.cleanup, label %for.body
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for.cond.cleanup: ; preds = %for.inc, %for.body.lr.ph
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%t2 = phi i32 [ %b, %for.body.lr.ph ], [ %mul.p, %for.inc ]
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%t1 = phi i32 [ %a, %for.body.lr.ph ], [ %add.p, %for.inc ]
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%add3 = add nsw i32 %t2, %t1
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ret i32 %add3
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}
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define void @foo_swapped(i32 %a, i32 %b) {
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;CHECK-LABEL: foo_swapped
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entry:
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br label %for.body
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;CHECK: entry:
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;CHECK-NEXT: %cmp1 = icmp eq i32 1, 2
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;CHECK-NEXT: br i1 %cmp1, label %entry.split, label %for.cond.cleanup.split, !prof !1
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;CHECK: for.body:
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for.body: ; preds = %for.inc, %entry
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%inc.i = phi i32 [ 0, %entry ], [ %inc, %if.then ]
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%add.i = phi i32 [ 100, %entry ], [ %add, %if.then ]
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%inc = add nuw nsw i32 %inc.i, 1
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%cmp1 = icmp eq i32 1, 2
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br i1 %cmp1, label %if.then, label %for.cond.cleanup, !prof !0
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if.then: ; preds = %for.body
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%add = add nsw i32 %a, %add.i
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%exitcond = icmp eq i32 %inc, %b
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br i1 %exitcond, label %for.cond.cleanup, label %for.body
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for.cond.cleanup: ; preds = %for.inc, %for.body.lr.ph, %for.body
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ret void
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}
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!0 = !{!"branch_weights", i32 64, i32 4}
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;CHECK: !0 = !{!"branch_weights", i32 64, i32 4}
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;CHECK: !1 = !{!"branch_weights", i32 4, i32 64}
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