Use branch reversal to do stuff like this:
call L_strcmp$stub
testl %eax, %eax
- jne LBB26_208 #cond_true6020
- jmp LBB26_227 #bb7119
+ je LBB26_227 #bb7119
LBB26_208: #cond_true6020
movl $l31_str14, 4(%esp)
testl %eax, %eax
- jne LBB26_704 #cond_true13042
- jmp LBB26_713 #bb13151
+ je LBB26_713 #bb13151
LBB26_704: #cond_true13042
movl $_str52, 4(%esp)
cmpl 76(%ecx), %eax
- jge LBB26_1628 #cond_false63.i.i
- jmp LBB26_1769 #_Z8makeGridP13mrSurfaceListidiidd.exit.i
+ jl LBB26_1769 #_Z8makeGridP13mrSurfaceListidiidd.exit.i
LBB26_1628: #cond_false63.i.i
movl $0, 48964(%esp)
llvm-svn: 31100
diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index 5be6baf..befcd00 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -472,6 +472,20 @@
++NumBranchOpts;
return OptimizeBlock(MBB);
}
+
+ // If the prior block branches here on true and somewhere else on false, and
+ // if the branch condition is reversible, reverse the branch to create a
+ // fall-through.
+ if (PriorTBB == &*MBB) {
+ std::vector<MachineOperand> NewPriorCond(PriorCond);
+ if (!TII->ReverseBranchCondition(NewPriorCond)) {
+ TII->RemoveBranch(PrevBB);
+ TII->InsertBranch(PrevBB, PriorFBB, 0, NewPriorCond);
+ MadeChange = true;
+ ++NumBranchOpts;
+ return OptimizeBlock(MBB);
+ }
+ }
}
// Analyze the branch in the current block.