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Fix for PR27750. Correctly handle the case where the fallthrough block and

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target block are the same in getFallThroughMBB.

Differential Revision: http://reviews.llvm.org/D20288

llvm-svn: 269760
This commit is contained in:
David L Kreitzer 2016-05-17 12:47:46 +00:00
parent 36892682d9
commit 874333eb48
2 changed files with 37 additions and 5 deletions
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14
lib/Target/X86/X86InstrInfo.cpp
View File

@ -3927,17 +3927,21 @@ bool X86InstrInfo::isUnpredicatedTerminator(const MachineInstr &MI) const {
return !isPredicated(MI);
}
// Given a MBB and its TBB, find the FBB which was a fallthrough MBB (it may not
// be a fallthorough MBB now due to layout changes). Return nullptr if the
// fallthough MBB cannot be identified.
// Given a MBB and its TBB, find the FBB which was a fallthrough MBB (it may
// not be a fallthrough MBB now due to layout changes). Return nullptr if the
// fallthrough MBB cannot be identified.
static MachineBasicBlock *getFallThroughMBB(MachineBasicBlock *MBB,
MachineBasicBlock *TBB) {
// Look for non-EHPad successors other than TBB. If we find exactly one, it
// is the fallthrough MBB. If we find zero, then TBB is both the target MBB
// and fallthrough MBB. If we find more than one, we cannot identify the
// fallthrough MBB and should return nullptr.
MachineBasicBlock *FallthroughBB = nullptr;
for (auto SI = MBB->succ_begin(), SE = MBB->succ_end(); SI != SE; ++SI) {
if ((*SI)->isEHPad() || *SI == TBB)
if ((*SI)->isEHPad() || (*SI == TBB && FallthroughBB))
continue;
// Return a nullptr if we found more than one fallthrough successor.
if (FallthroughBB)
if (FallthroughBB && FallthroughBB != TBB)
return nullptr;
FallthroughBB = *SI;
}

28
test/CodeGen/X86/fp-une-cmp.ll
View File

@ -102,6 +102,34 @@ if.end:
ret void
}
; Test that an FP oeq/une conditional branch can be inverted successfully even
; when the true and false targets are the same (PR27750).
;
; CHECK-LABEL: pr27750
; CHECK: ucomiss
; CHECK-NEXT: jne [[TARGET:.*]]
; CHECK-NEXT: jp [[TARGET]]
define void @pr27750(i32* %b, float %x, i1 %y) {
entry:
br label %for.cond
for.cond:
br label %for.cond1
for.cond1:
br i1 %y, label %for.body3.lr.ph, label %for.end
for.body3.lr.ph:
store i32 0, i32* %b, align 4
br label %for.end
for.end:
; After block %for.cond gets eliminated, the two target blocks of this
; conditional block are the same.
%tobool = fcmp une float %x, 0.000000e+00
br i1 %tobool, label %for.cond, label %for.cond1
}
declare void @a()
!1 = !{!"branch_weights", i32 1, i32 1000}