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[EarlyIfConversion] Don't if-convert unconditional branches.

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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
This commit is contained in:
Eli Friedman 2019-01-15 00:19:46 +00:00
parent d0fe48e3c6
commit 80ce92a205
2 changed files with 36 additions and 0 deletions
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7
lib/CodeGen/EarlyIfConversion.cpp
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@ -398,6 +398,13 @@ bool SSAIfConv::canConvertIf(MachineBasicBlock *MBB) {
return false;
}
// Make sure the analyzed branch is conditional; one of the successors
// could be a landing pad. (Empty landing pads can be generated on Windows.)
if (Cond.empty()) {
LLVM_DEBUG(dbgs() << "AnalyzeBranch found an unconditional branch.\n");
return false;
}
// AnalyzeBranch doesn't set FBB on a fall-through branch.
// Make sure it is always set.
FBB = TBB == Succ0 ? Succ1 : Succ0;

29
test/CodeGen/AArch64/landingpad-ifcvt.ll Normal file
View File

@ -0,0 +1,29 @@
; RUN: llc < %s | FileCheck %s
; Make sure this doesn't crash (and the output is sane).
; CHECK: ; %__except.ret
; CHECK-NEXT: mov x0, xzr
target datalayout = "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-pc-windows-msvc19.11.0"
define i64 @f(i32* %hwnd, i32 %message, i64 %wparam, i64 %lparam) personality i8* bitcast (i32 (...)* @__C_specific_handler to i8*) {
entry:
%call = invoke i64 @callee(i32* %hwnd, i32 %message, i64 %wparam, i64 %lparam)
to label %__try.cont unwind label %catch.dispatch
catch.dispatch: ; preds = %entry
%0 = catchswitch within none [label %__except.ret] unwind to caller
__except.ret: ; preds = %catch.dispatch
%1 = catchpad within %0 [i8* bitcast (i32 (i8*, i8*)* @filt to i8*)]
catchret from %1 to label %__try.cont
__try.cont: ; preds = %__except.ret, %entry
%rv.0 = phi i64 [ 0, %__except.ret ], [ %call, %entry ]
ret i64 %rv.0
}
declare dso_local i64 @callee(i32*, i32, i64, i64)
declare i32 @filt(i8*, i8* nocapture readnone)
declare dso_local i32 @__C_specific_handler(...)