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ba862f13cb
Some benchmarks have shown that this could lead to a potential performance benefit, and so adding some flags to try to help measure the difference. A possible explanation. In diamond-shaped CFGs (A followed by either B or C both followed by D), putting B and C both in between A and D leads to the code being less dense than it could be. Always either B or C have to be skipped increasing the chance of cache misses etc. Moving either B or C to after D might be beneficial on average. In the long run, but we should probably do a better job of analyzing the basic block and branch probabilities to move the correct one of B or C to after D. But even if we don't use this in the long run, it is a good baseline for benchmarking. Original patch authored by Daniel Jasper with test tweaks and a second flag added by me. Differential Revision: http://reviews.llvm.org/D6969 llvm-svn: 226034
113 lines
2.4 KiB
LLVM
113 lines
2.4 KiB
LLVM
; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux < %s | FileCheck %s -check-prefix=CHECK-BAD-CFG
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; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux -no-bad-cfg-conflict-check < %s | FileCheck %s -check-prefix=CHECK-NO-BAD-CFG
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; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux -only-hot-bad-cfg-conflict-check < %s | FileCheck %s -check-prefix=CHECK-HOT-BAD-CFG
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define void @foo(i32 %t) {
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; Test that we lift the call to 'c' up to immediately follow the call to 'b'
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; when we disable the cfg conflict check.
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;
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; CHECK-BAD-CFG-LABEL: foo:
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; CHECK-BAD-CFG: callq b
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; CHECK-BAD-CFG: callq a
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; CHECK-BAD-CFG: callq c
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;
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; CHECK-NO-BAD-CFG-LABEL: foo:
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; CHECK-NO-BAD-CFG: callq b
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; CHECK-NO-BAD-CFG: callq c
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; CHECK-NO-BAD-CFG: callq a
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;
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; CHECK-HOT-BAD-CFG-LABEL: foo:
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; CHECK-HOT-BAD-CFG: callq b
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; CHECK-HOT-BAD-CFG: callq c
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; CHECK-HOT-BAD-CFG: callq a
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entry:
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%cmp = icmp eq i32 %t, 0
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br i1 %cmp, label %if.then, label %if.else
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if.then:
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call void @a()
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br label %if.end
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if.else:
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call void @b()
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br label %if.end
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if.end:
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call void @c()
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ret void
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}
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define void @bar(i32 %t1, i32 %t2, i32 %t3) {
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; Test that we lift the call to 'c' up to immediately follow the call to 'b'
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; when we disable the cfg conflict check.
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;
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; CHECK-BAD-CFG-LABEL: bar:
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; CHECK-BAD-CFG: callq a
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; CHECK-BAD-CFG: callq c
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; CHECK-BAD-CFG: callq d
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; CHECK-BAD-CFG: callq f
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; CHECK-BAD-CFG: callq b
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; CHECK-BAD-CFG: callq e
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; CHECK-BAD-CFG: callq g
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;
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; CHECK-NO-BAD-CFG-LABEL: bar:
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; CHECK-NO-BAD-CFG: callq a
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; CHECK-NO-BAD-CFG: callq c
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; CHECK-NO-BAD-CFG: callq g
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; CHECK-NO-BAD-CFG: callq d
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; CHECK-NO-BAD-CFG: callq f
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; CHECK-NO-BAD-CFG: callq b
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; CHECK-NO-BAD-CFG: callq e
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;
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; CHECK-HOT-BAD-CFG-LABEL: bar:
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; CHECK-HOT-BAD-CFG: callq a
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; CHECK-HOT-BAD-CFG: callq c
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; CHECK-HOT-BAD-CFG: callq d
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; CHECK-HOT-BAD-CFG: callq f
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; CHECK-HOT-BAD-CFG: callq g
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; CHECK-HOT-BAD-CFG: callq b
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; CHECK-HOT-BAD-CFG: callq e
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entry:
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br i1 undef, label %if1.then, label %if1.else
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if1.then:
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call void @a()
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%cmp2 = icmp eq i32 %t2, 0
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br i1 %cmp2, label %if2.then, label %if2.else
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if2.then:
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call void @b()
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br label %if.end
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if2.else:
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call void @c()
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br label %if.end
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if1.else:
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call void @d()
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%cmp3 = icmp eq i32 %t3, 0
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br i1 %cmp3, label %if3.then, label %if3.else
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if3.then:
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call void @e()
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br label %if.end
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if3.else:
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call void @f()
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br label %if.end
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if.end:
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call void @g()
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ret void
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}
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declare void @a()
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declare void @b()
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declare void @c()
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declare void @d()
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declare void @e()
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declare void @f()
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declare void @g()
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