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[EarlyIfConversion] Don't if-convert unconditional branches.
A block ending in an unconditional branch can have two successors if one is a landing pad. In practice, I think this only has an effect on Windows because landing pads are never empty for Itanium unwinding. (Alternatively, I could add a check to AArch64InstrInfo::canInsertSelect, but this seems more obvious.) Differential Revision: https://reviews.llvm.org/D56468 llvm-svn: 351142
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@ -398,6 +398,13 @@ bool SSAIfConv::canConvertIf(MachineBasicBlock *MBB) {
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return false;
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}
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// Make sure the analyzed branch is conditional; one of the successors
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// could be a landing pad. (Empty landing pads can be generated on Windows.)
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if (Cond.empty()) {
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LLVM_DEBUG(dbgs() << "AnalyzeBranch found an unconditional branch.\n");
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return false;
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}
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// AnalyzeBranch doesn't set FBB on a fall-through branch.
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// Make sure it is always set.
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FBB = TBB == Succ0 ? Succ1 : Succ0;
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29
test/CodeGen/AArch64/landingpad-ifcvt.ll
Normal file
29
test/CodeGen/AArch64/landingpad-ifcvt.ll
Normal file
@ -0,0 +1,29 @@
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; RUN: llc < %s | FileCheck %s
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; Make sure this doesn't crash (and the output is sane).
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; CHECK: ; %__except.ret
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; CHECK-NEXT: mov x0, xzr
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target datalayout = "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"
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target triple = "aarch64-pc-windows-msvc19.11.0"
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define i64 @f(i32* %hwnd, i32 %message, i64 %wparam, i64 %lparam) personality i8* bitcast (i32 (...)* @__C_specific_handler to i8*) {
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entry:
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%call = invoke i64 @callee(i32* %hwnd, i32 %message, i64 %wparam, i64 %lparam)
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to label %__try.cont unwind label %catch.dispatch
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catch.dispatch: ; preds = %entry
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%0 = catchswitch within none [label %__except.ret] unwind to caller
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__except.ret: ; preds = %catch.dispatch
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%1 = catchpad within %0 [i8* bitcast (i32 (i8*, i8*)* @filt to i8*)]
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catchret from %1 to label %__try.cont
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__try.cont: ; preds = %__except.ret, %entry
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%rv.0 = phi i64 [ 0, %__except.ret ], [ %call, %entry ]
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ret i64 %rv.0
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}
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declare dso_local i64 @callee(i32*, i32, i64, i64)
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declare i32 @filt(i8*, i8* nocapture readnone)
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declare dso_local i32 @__C_specific_handler(...)
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