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Don't add CFG edges for redundant conditional branches.

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IR that hasn't been through SimplifyCFG can look like this:

  br i1 %b, label %r, label %r

Make sure we don't create duplicate Machine CFG edges in this case.

Fix the machine code verifier to accept conditional branches with a
single CFG edge.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162230 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2012-08-20 21:39:52 +00:00
parent 2c5a960b0e
commit e7fdef420d
3 changed files with 23 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/CodeGen/MachineVerifier.cpp
+18 -2
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@@ -580,7 +580,15 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
++MBBI;
if (MBBI == MF->end()) {
report("MBB conditionally falls through out of function!", MBB);
} if (MBB->succ_size() != 2) {
} if (MBB->succ_size() == 1) {
// A conditional branch with only one successor is weird, but allowed.
if (&*MBBI != TBB)
report("MBB exits via conditional branch/fall-through but only has "
"one CFG successor!", MBB);
else if (TBB != *MBB->succ_begin())
report("MBB exits via conditional branch/fall-through but the CFG "
"successor don't match the actual successor!", MBB);
} else if (MBB->succ_size() != 2) {
report("MBB exits via conditional branch/fall-through but doesn't have "
"exactly two CFG successors!", MBB);
} else if (!matchPair(MBB->succ_begin(), TBB, MBBI)) {
@@ -600,7 +608,15 @@ MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
} else if (TBB && FBB) {
// Block conditionally branches somewhere, otherwise branches
// somewhere else.
if (MBB->succ_size() != 2) {
if (MBB->succ_size() == 1) {
// A conditional branch with only one successor is weird, but allowed.
if (FBB != TBB)
report("MBB exits via conditional branch/branch through but only has "
"one CFG successor!", MBB);
else if (TBB != *MBB->succ_begin())
report("MBB exits via conditional branch/branch through but the CFG "
"successor don't match the actual successor!", MBB);
} else if (MBB->succ_size() != 2) {
report("MBB exits via conditional branch/branch but doesn't have "
"exactly two CFG successors!", MBB);
} else if (!matchPair(MBB->succ_begin(), TBB, FBB)) {