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enhance the "change or icmp's into switch" xform to handle one value in an

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'or sequence' that it doesn't understand.  This allows us to optimize
something insane like this:

int crud (unsigned char c, unsigned x)
 {
   if(((((((((( (int) c <= 32 ||
                    (int) c == 46) || (int) c == 44)
                  || (int) c == 58) || (int) c == 59) || (int) c == 60)
               || (int) c == 62) || (int) c == 34) || (int) c == 92)
            || (int) c == 39) != 0)
     foo();
 }

into:

define i32 @crud(i8 zeroext %c, i32 %x) nounwind ssp noredzone {
entry:
  %cmp = icmp ult i8 %c, 33
  br i1 %cmp, label %if.then, label %switch.early.test

switch.early.test:                                ; preds = %entry
  switch i8 %c, label %if.end [
    i8 39, label %if.then
    i8 44, label %if.then
    i8 58, label %if.then
    i8 59, label %if.then
    i8 60, label %if.then
    i8 62, label %if.then
    i8 46, label %if.then
    i8 92, label %if.then
    i8 34, label %if.then
  ]

by pulling the < comparison out ahead of the newly formed switch.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121680 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-12-13 04:50:38 +00:00
parent f5198e7fe3
commit 7312a22ed6
2 changed files with 69 additions and 4 deletions
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48
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -301,6 +301,7 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra,
Instruction *I = dyn_cast<Instruction>(V);
if (I == 0) return 0;
// If this is an icmp against a constant, handle this as one of the cases.
if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) {
if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE))
if (ConstantInt *C = GetConstantInt(I->getOperand(1), TD)) {
@ -310,17 +311,43 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra,
return 0;
}
// Otherwise, we can only handle an | or &, depending on isEQ.
if (I->getOpcode() != (isEQ ? Instruction::Or : Instruction::And))
return 0;
unsigned NumValsBeforeLHS = Vals.size();
if (Value *LHS = GatherConstantCompares(I->getOperand(0), Vals, Extra, TD,
isEQ)) {
unsigned NumVals = Vals.size();
if (Value *RHS = GatherConstantCompares(I->getOperand(1), Vals, Extra, TD,
isEQ)) {
if (LHS == RHS)
return LHS;
}
Vals.resize(NumVals);
// The RHS of the or/and can't be folded in and we haven't used "Extra" yet,
// set it and return success.
if (Extra == 0 || Extra == I->getOperand(1)) {
Extra = I->getOperand(1);
return LHS;
}
Vals.resize(NumValsBeforeLHS);
return 0;
}
// If the LHS can't be folded in, but Extra is available and RHS can, try to
// use LHS as Extra.
if (Extra == 0 || Extra == I->getOperand(0)) {
Extra = I->getOperand(0);
if (Value *RHS = GatherConstantCompares(I->getOperand(1), Vals, Extra, TD,
isEQ))
return RHS;
Vals.resize(NumValsBeforeLHS);
Extra = 0;
}
return 0;
}
@ -2059,7 +2086,9 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
}
}
if (CompVal) {
// We do this transformation if we'll end up creating a switch with at
// least two values if Extra is used.
if (CompVal && (!ExtraCase || Values.size() > 1)) {
// There might be duplicate constants in the list, which the switch
// instruction can't handle, remove them now.
array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate);
@ -2070,6 +2099,19 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
BasicBlock *EdgeBB = BI->getSuccessor(0);
if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
// If there are any extra values that couldn't be folded into the switch
// then we evaluate them with an explicit branch first. Split the block
// right before the condbr to handle it.
if (ExtraCase) {
BasicBlock *NewBB = BB->splitBasicBlock(BI, "switch.early.test");
// Remove the uncond branch added to the old block.
TerminatorInst *OldTI = BB->getTerminator();
BranchInst::Create(EdgeBB, NewBB, ExtraCase, OldTI);
OldTI->eraseFromParent();
BB = NewBB;
}
// Convert pointer to int before we switch.
if (CompVal->getType()->isPointerTy()) {
assert(TD && "Cannot switch on pointer without TargetData");
@ -2079,8 +2121,8 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) {
}
// Create the new switch instruction now.
SwitchInst *New = SwitchInst::Create(CompVal, DefaultBB,
Values.size(), BI);
SwitchInst *New =
SwitchInst::Create(CompVal, DefaultBB, Values.size(), BI);
// Add all of the 'cases' to the switch instruction.
for (unsigned i = 0, e = Values.size(); i != e; ++i)

25
test/Transforms/SimplifyCFG/switch_create.ll
View File

@ -149,7 +149,30 @@ UnifiedReturnBlock: ; preds = %shortcirc_done.4, %shortcirc_next.4
; CHECK: i32 18, label %UnifiedReturnBlock
; CHECK: i32 19, label %switch.edge
; CHECK: ]
}
define void @test7(i8 zeroext %c, i32 %x) nounwind ssp noredzone {
entry:
%cmp = icmp ult i32 %x, 32
%cmp4 = icmp eq i8 %c, 97
%or.cond = or i1 %cmp, %cmp4
%cmp9 = icmp eq i8 %c, 99
%or.cond11 = or i1 %or.cond, %cmp9
br i1 %or.cond11, label %if.then, label %if.end
if.then: ; preds = %entry
tail call void @foo1() nounwind noredzone
ret void
if.end: ; preds = %entry
ret void
; CHECK: @test7
; CHECK: %cmp = icmp ult i32 %x, 32
; CHECK: br i1 %cmp, label %if.then, label %switch.early.test
; CHECK: switch.early.test:
; CHECK: switch i8 %c, label %if.end [
; CHECK: i8 99, label %if.then
; CHECK: i8 97, label %if.then
; CHECK: ]
}