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[X86] Don't model UD2/UD2B as a terminator

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A UD2 might make its way into the program via a call to @llvm.trap.
Obviously, calls are not terminators.  However, we modeled the X86
instruction, UD2, as a terminator.  Later on, this confuses the epilogue
insertion machinery which results in the epilogue getting inserted
before the UD2.  For some platforms, like x64, the result is a
violation of the ABI.

Instead, model UD2/UD2B as a side effecting instruction which may
observe memory.

llvm-svn: 278144
This commit is contained in:
David Majnemer 2016-08-09 17:55:12 +00:00
parent 9d3d169916
commit a3d1356e37
2 changed files with 6 additions and 1 deletions
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2
lib/Target/X86/X86InstrSystem.td
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@ -23,7 +23,7 @@ let Defs = [RAX, RCX, RDX] in
// CPU flow control instructions
let isTerminator = 1, isBarrier = 1, hasCtrlDep = 1 in {
let mayLoad = 1, mayStore = 0, hasSideEffects = 1 in {
def TRAP : I<0x0B, RawFrm, (outs), (ins), "ud2", [(trap)]>, TB;
def UD2B : I<0xB9, RawFrm, (outs), (ins), "ud2b", []>, TB;
}

5
test/CodeGen/X86/x86-framelowering-trap.ll
View File

@ -3,13 +3,18 @@ target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; CHECK-LABEL: bar:
; CHECK: pushq
; CHECK: ud2
; CHECK-NEXT: popq
; CHECK-NEXT: retq
define void @bar() {
entry:
call void @callee()
call void @llvm.trap()
ret void
}
; Function Attrs: noreturn nounwind
declare void @llvm.trap()
declare void @callee()