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13c6dece14
Here we make ScalarEvolution::isKnownPredicate, indirectly, a little smarter.
Given some relational comparison operator OP, and two AddRec SCEVs, {I,+,S} OP
{J,+,T}, we can reduce this to the comparison I OP J when S == T, both AddRecs
are for the same loop, and both are known not to wrap.
As it turns out, because of the way that backedge-guard expressions can be
leveraged when computing known predicates, this allows indvars to simplify the
if-statement comparison in this loop:
void foo (int *a, int *b, int n) {
for (int i = 0; i < n; ++i) {
if (i > n)
a[i] = b[i] + 1;
}
}
which, somewhat surprisingly, we were not previously optimizing away.
llvm-svn: 245400
48 lines
1.6 KiB
LLVM
48 lines
1.6 KiB
LLVM
; RUN: opt -S -indvars < %s | FileCheck %s
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target datalayout = "E-m:e-i64:64-n32:64"
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target triple = "powerpc64-unknown-linux-gnu"
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; Function Attrs: nounwind
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define void @foo(i32* nocapture %a, i32* nocapture readonly %b, i32 signext %n) #0 {
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entry:
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; CHECK-LABEL: @foo
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%cmp.10 = icmp sgt i32 %n, 0
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br i1 %cmp.10, label %for.body.lr.ph, label %for.cond.cleanup
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for.body.lr.ph: ; preds = %entry
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br label %for.body
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for.cond.for.cond.cleanup_crit_edge: ; preds = %for.inc
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br label %for.cond.cleanup
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for.cond.cleanup: ; preds = %for.cond.for.cond.cleanup_crit_edge, %entry
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ret void
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for.body: ; preds = %for.body.lr.ph, %for.inc
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%i.011 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.inc ]
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%cmp1 = icmp sgt i32 %i.011, %n
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br i1 %cmp1, label %if.then, label %for.inc
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; CHECK-NOT: br i1 %cmp1, label %if.then, label %for.inc
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; CHECK: br i1 false, label %if.then, label %for.inc
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if.then: ; preds = %for.body
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%idxprom = sext i32 %i.011 to i64
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%arrayidx = getelementptr inbounds i32, i32* %b, i64 %idxprom
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%0 = load i32, i32* %arrayidx, align 4
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%add = add nsw i32 %0, 1
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%arrayidx3 = getelementptr inbounds i32, i32* %a, i64 %idxprom
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store i32 %add, i32* %arrayidx3, align 4
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br label %for.inc
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for.inc: ; preds = %for.body, %if.then
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%inc = add nsw i32 %i.011, 1
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%cmp = icmp slt i32 %inc, %n
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br i1 %cmp, label %for.body, label %for.cond.for.cond.cleanup_crit_edge
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}
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attributes #0 = { nounwind }
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