[llvm-commits] [llvm] r121680 - in /llvm/trunk: lib/Transforms/Utils/SimplifyCFG.cpp test/Transforms/SimplifyCFG/switch_create.ll
Chris Lattner
sabre at nondot.org
Sun Dec 12 20:50:39 PST 2010
Author: lattner
Date: Sun Dec 12 22:50:38 2010
New Revision: 121680
URL: http://llvm.org/viewvc/llvm-project?rev=121680&view=rev
Log:
enhance the "change or icmp's into switch" xform to handle one value in an
'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.
Modified:
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/trunk/test/Transforms/SimplifyCFG/switch_create.ll
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=121680&r1=121679&r2=121680&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Sun Dec 12 22:50:38 2010
@@ -301,6 +301,7 @@
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 @@
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 @@
}
}
- 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 @@
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 @@
}
// 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)
Modified: llvm/trunk/test/Transforms/SimplifyCFG/switch_create.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/switch_create.ll?rev=121680&r1=121679&r2=121680&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/switch_create.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/switch_create.ll Sun Dec 12 22:50:38 2010
@@ -149,7 +149,30 @@
; 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: ]
+}
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