2010-11-18 18:05:13 +01:00
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; RUN: opt -basicaa -gvn -S < %s | FileCheck %s
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target datalayout = "e-p:64:64:64"
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; CHECK: @foo
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; CHECK: entry.end_crit_edge:
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; CHECK: %n.pre = load i32* %q.phi.trans.insert
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; CHECK: then:
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; CHECK: store i32 %z
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; CHECK: end:
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; CHECK: %n = phi i32 [ %n.pre, %entry.end_crit_edge ], [ %z, %then ]
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; CHECK: ret i32 %n
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@G = external global [100 x i32]
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define i32 @foo(i32 %x, i32 %z) {
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entry:
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GVN does simple propagation of conditions: when it sees a conditional
branch "br i1 %x, label %if_true, label %if_false" then it replaces
"%x" with "true" in places only reachable via the %if_true arm, and
with "false" in places only reachable via the %if_false arm. Except
that actually it doesn't: if value numbering shows that %y is equal
to %x then, yes, %y will be turned into true/false in this way, but
any occurrences of %x itself are not transformed. Fix this. What's
more, it's often the case that %x is an equality comparison such as
"%x = icmp eq %A, 0", in which case every occurrence of %A that is
only reachable via the %if_true arm can be replaced with 0. Implement
this and a few other variations on this theme. This reduces the number
of lines of LLVM IR in "GCC as one big file" by 0.2%. It has a bigger
impact on Ada code, typically reducing the number of lines of bitcode
by around 0.4% by removing repeated compiler generated checks. Passes
the LLVM nightly testsuite and the Ada ACATS testsuite.
llvm-svn: 141177
2011-10-05 16:28:49 +02:00
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%tobool = icmp eq i32 %z, 0
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2010-11-18 18:05:13 +01:00
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br i1 %tobool, label %end, label %then
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then:
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%i = sext i32 %x to i64
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%p = getelementptr [100 x i32]* @G, i64 0, i64 %i
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store i32 %z, i32* %p
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br label %end
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end:
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%j = sext i32 %x to i64
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%q = getelementptr [100 x i32]* @G, i64 0, i64 %j
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%n = load i32* %q
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ret i32 %n
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}
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