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SimplifyCFG: Expose phi node folding cost threshold as command line parameter

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llvm-svn: 130528
This commit is contained in:
Peter Collingbourne 2011-04-29 18:47:38 +00:00
parent 0994e869f9
commit d78bf257ad
2 changed files with 40 additions and 1 deletions
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7
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -37,6 +37,10 @@
#include <map>
using namespace llvm;
static cl::opt<unsigned>
PHINodeFoldingThreshold("phi-node-folding-threshold", cl::Hidden, cl::init(1),
cl::desc("Control the amount of phi node folding to perform (default = 1)"));
static cl::opt<bool>
DupRet("simplifycfg-dup-ret", cl::Hidden, cl::init(false),
cl::desc("Duplicate return instructions into unconditional branches"));
@ -1246,7 +1250,8 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) {
// instructions. While we are at it, keep track of the instructions
// that need to be moved to the dominating block.
SmallPtrSet<Instruction*, 4> AggressiveInsts;
unsigned MaxCostVal0 = 1, MaxCostVal1 = 1;
unsigned MaxCostVal0 = PHINodeFoldingThreshold,
MaxCostVal1 = PHINodeFoldingThreshold;
for (BasicBlock::iterator II = BB->begin(); isa<PHINode>(II);) {
PHINode *PN = cast<PHINode>(II++);

34
test/Transforms/SimplifyCFG/PhiEliminate3.ll Normal file
View File

@ -0,0 +1,34 @@
; Test merging of blocks containing complex expressions,
; with various folding thresholds
;
; RUN: opt < %s -simplifycfg -S -phi-node-folding-threshold=1 | grep N:
; RUN: opt < %s -simplifycfg -S -phi-node-folding-threshold=2 | not grep N:
; RUN: opt < %s -simplifycfg -S -phi-node-folding-threshold=2 | grep M:
; RUN: opt < %s -simplifycfg -S -phi-node-folding-threshold=7 | not grep M:
;
define i32 @test(i1 %a, i1 %b, i32 %i, i32 %j, i32 %k) {
entry:
br i1 %a, label %M, label %O
O:
br i1 %b, label %P, label %Q
P:
%iaj = add i32 %i, %j
%iajak = add i32 %iaj, %k
br label %N
Q:
%ixj = xor i32 %i, %j
%ixjxk = xor i32 %ixj, %k
br label %N
N:
; This phi should be foldable if threshold >= 2
%Wp = phi i32 [ %iajak, %P ], [ %ixjxk, %Q ]
%Wp2 = add i32 %Wp, %Wp
br label %M
M:
; This phi should be foldable if threshold >= 7
%W = phi i32 [ %Wp2, %N ], [ 2, %entry ]
%R = add i32 %W, 1
ret i32 %R
}