ca12d1d8f1
This commit addresses a shortcoming in the implementation of `combineBR_CCMASK` and `combineSELECT_CCMASK`. In cases where `combineCCMask` was able to reduce the ccmask going into the select or branch to either true (`ccvalid`) or false (`0`), a trivial instruction would be emitted (i.e. either a select that would only ever select one side, or a conditional branch with `true` or `false` as the branch condition). This led under certain circumstances to, e.g., `BRC` instructions being emitted that triggered an assert in the AsmPrinter meant to exclude such branch conditions. For the select case, this commit introduces an early bailout that simply returns the value that would "always" be selected. For the branch case, the commit introduces an additional guard that prevents the DAGCombine from taking effect, thereby preventing the illegal instruction from being emitted.
29 lines
861 B
LLVM
29 lines
861 B
LLVM
; Test that a conditional branch with a discoverably trivial condition
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; does not result in an invalid conditional branch instruction.
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;
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; RUN: llc < %s -verify-machineinstrs -mtriple=s390x-linux-gnu -mcpu=z13 \
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; RUN: --stop-after=systemz-isel | FileCheck %s
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@g_1 = dso_local local_unnamed_addr global i64 0, align 8
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@g_2 = dso_local local_unnamed_addr global i32 0, align 4
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define dso_local void @f1() local_unnamed_addr #1 {
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entry:
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;CHECK-LABEL: f1
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;CHECK-NOT: BRC 14, 0, %bb.2
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%0 = load i64, ptr @g_1, align 8
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%tobool.not = icmp eq i64 %0, 0
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%sub.i = select i1 %tobool.not, i8 4, i8 3
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%conv1 = zext nneg i8 %sub.i to i32
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store i32 %conv1, ptr @g_2, align 4
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%.pr = load i32, ptr @g_2, align 4
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%tobool5.not = icmp eq i32 %.pr, 0
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br i1 %tobool5.not, label %for.cond, label %lbl_1
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lbl_1:
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br label %lbl_1
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for.cond:
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br label %for.cond
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}
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