llvm-6502/test/Transforms/InstCombine/branch.ll at c88eae46da43652874c728fa686cde7a49b49863 - llvm-6502 - Applefritter: Git

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Philip Reames fb4ffccacb If a conditional branch jumps to the same target, remove the condition

Given that large parts of inst combine is restricted to instructions which have one use, getting rid of a use on the condition can help the effectiveness of the optimizer. Also, it allows the condition to potentially be deleted by instcombine rather than waiting for another pass.

I noticed this completely by accident in another test case. It's not anything that actually came from a real workload.

p.s. We should probably do the same thing for switch instructions.

Differential Revision: http://reviews.llvm.org/D8220



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231881 91177308-0d34-0410-b5e6-96231b3b80d8

2015-03-10 22:52:37 +00:00

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 ; RUN: opt -instcombine -S < %s | FileCheck %s
 define i32 @test(i32 %x) {
 ; CHECK-LABEL: @test
 entry:
 ; CHECK-NOT: icmp
 ; CHECK: br i1 undef,
   %cmp = icmp ult i32 %x, 7
   br i1 %cmp, label %merge, label %merge
 merge:
 ; CHECK-LABEL: merge:
 ; CHECK: ret i32 %x
   ret i32 %x
 }