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Transform code like:

Browse Source 
jle FOO
  jmp BAR
BAR:

into:

  jle FOO
BAR:

... whoa!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31098 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-10-21 05:43:30 +00:00
parent 879d09cf13
commit 2d47bd937c
1 changed files with 13 additions and 2 deletions
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15
lib/CodeGen/BranchFolding.cpp
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@ -30,7 +30,7 @@ using namespace llvm;
static Statistic<> NumDeadBlocks("branchfold", "Number of dead blocks removed");
static Statistic<> NumBranchOpts("branchfold", "Number of branches optimized");
static Statistic<> NumTailMerge ("branchfold", "Number of block tails merged");
static cl::opt<bool> EnableTailMerge("enable-tail-merge");
static cl::opt<bool> EnableTailMerge("enable-tail-merge", cl::init(false));
namespace {
struct BranchFolder : public MachineFunctionPass {
@ -442,7 +442,8 @@ void BranchFolder::OptimizeBlock(MachineFunction::iterator MBB) {
!PriorCond.empty(), MBB);
// If the previous branch is conditional and both conditions go to the same
// destination, remove the branch, replacing it with an unconditional one.
// destination, remove the branch, replacing it with an unconditional one or
// a fall-through.
if (PriorTBB && PriorTBB == PriorFBB) {
TII->RemoveBranch(PrevBB);
PriorCond.clear();
@ -461,6 +462,16 @@ void BranchFolder::OptimizeBlock(MachineFunction::iterator MBB) {
++NumBranchOpts;
return OptimizeBlock(MBB);
}
// If the prior block branches somewhere else on the condition and here if
// the condition is false, remove the uncond second branch.
if (PriorFBB == &*MBB) {
TII->RemoveBranch(PrevBB);
TII->InsertBranch(PrevBB, PriorTBB, 0, PriorCond);
MadeChange = true;
++NumBranchOpts;
return OptimizeBlock(MBB);
}
}
// Analyze the branch in the current block.