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b3ecd3b03e
System z branches have a mask to select which of the 4 CC values should cause the branch to be taken. We can invert a branch by inverting the mask. However, not all instructions can produce all 4 CC values, so inverting the branch like this can lead to some oddities. For example, integer comparisons only produce a CC of 0 (equal), 1 (less) or 2 (greater). If an integer EQ is reversed to NE before instruction selection, the branch will test for 1 or 2. If instead the branch is reversed after instruction selection (by inverting the mask), it will test for 1, 2 or 3. Both are correct, but the second isn't really canonical. This patch therefore keeps track of which CC values are possible and uses this when inverting a mask. Although this is mostly cosmestic, it fixes undefined behavior for the CIJNLH in branch-08.ll. Another fix would have been to mask out bit 0 when generating the fused compare and branch, but the point of this patch is that we shouldn't need to do that in the first place. The patch also makes it easier to reuse CC results from other instructions. llvm-svn: 187495
46 lines
915 B
LLVM
46 lines
915 B
LLVM
; Test SystemZInstrInfo::AnalyzeBranch and SystemZInstrInfo::InsertBranch.
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;
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; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
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declare void @foo() noreturn
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; Check a case where a separate branch is needed and where the original
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; order should be reversed.
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define i32 @f1(i32 %a, i32 %b) {
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; CHECK-LABEL: f1:
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; CHECK: clr %r2, %r3
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; CHECK: jl .L[[LABEL:.*]]
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; CHECK: br %r14
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; CHECK: .L[[LABEL]]:
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; CHECK: brasl %r14, foo@PLT
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entry:
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%cmp = icmp ult i32 %a, %b
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br i1 %cmp, label %callit, label %return
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callit:
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call void @foo()
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unreachable
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return:
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ret i32 1
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}
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; Same again with a fused compare and branch.
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define i32 @f2(i32 %a) {
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; CHECK-LABEL: f2:
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; CHECK: cije %r2, 0, .L[[LABEL:.*]]
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; CHECK: br %r14
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; CHECK: .L[[LABEL]]:
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; CHECK: brasl %r14, foo@PLT
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entry:
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%cmp = icmp eq i32 %a, 0
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br i1 %cmp, label %callit, label %return
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callit:
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call void @foo()
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unreachable
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return:
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ret i32 1
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}
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