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Teach IRCE to look at branch weights when recognizing range checks

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Splitting a loop to make range checks redundant is profitable only if
the range check "never" fails. Make this fact a part of recognizing a
range check -- a branch is a range check only if it is expected to
pass (via branch_weights metadata).

Differential Revision: http://reviews.llvm.org/D7192



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227249 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das
2015-01-27 21:38:12 +00:00
parent 00b7a940e7
commit fdefc694cd
6 changed files with 72 additions and 17 deletions
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3
test/Transforms/IRCE/single-access-with-preloop.ll
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@@ -13,7 +13,7 @@ define void @single_access_with_preloop(i32 *%arr, i32 *%a_len_ptr, i32 %n, i32
%abc.high = icmp slt i32 %array.idx, %len
%abc.low = icmp sge i32 %array.idx, 0
%abc = and i1 %abc.low, %abc.high
br i1 %abc, label %in.bounds, label %out.of.bounds
br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
in.bounds:
%addr = getelementptr i32* %arr, i32 %array.idx
@@ -57,3 +57,4 @@ define void @single_access_with_preloop(i32 *%arr, i32 *%a_len_ptr, i32 %n, i32
; CHECK: br i1 %next.postloop, label %loop.postloop, label %exit.loopexit
!0 = !{i32 0, i32 2147483647}
!1 = !{!"branch_weights", i32 64, i32 4}