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Limit the icmp+phi merging optimization to the cases where it is profitable:

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don't make i1 phis when it won't be possible to eliminate them.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52097 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-06-08 20:52:11 +00:00
parent c4e6b37329
commit 7d8ab4efbc
2 changed files with 61 additions and 4 deletions
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16
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -5043,8 +5043,12 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
switch (LHSI->getOpcode()) {
case Instruction::PHI:
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
// Only fold fcmp into the PHI if the phi and fcmp are in the same
// block. If in the same block, we're encouraging jump threading. If
// not, we are just pessimizing the code by making an i1 phi.
if (LHSI->getParent() == I.getParent())
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
break;
case Instruction::SIToFP:
case Instruction::UIToFP:
@ -5348,8 +5352,12 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
break;
case Instruction::PHI:
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
// Only fold icmp into the PHI if the phi and fcmp are in the same
// block. If in the same block, we're encouraging jump threading. If
// not, we are just pessimizing the code by making an i1 phi.
if (LHSI->getParent() == I.getParent())
if (Instruction *NV = FoldOpIntoPhi(I))
return NV;
break;
case Instruction::Select: {
// If either operand of the select is a constant, we can fold the

49
test/Transforms/InstCombine/2008-06-08-ICmpPHI.ll Normal file
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@ -0,0 +1,49 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {phi i32} | count 2
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i386-apple-darwin8"
define void @test() nounwind {
entry:
br label %bb
bb: ; preds = %bb16, %entry
%i.0 = phi i32 [ 0, %entry ], [ %indvar.next, %somebb ] ; <i32> [#uses=1]
%x.0 = phi i32 [ 37, %entry ], [ %tmp17, %somebb ] ; <i32> [#uses=1]
%tmp = tail call i32 (...)* @bork( ) nounwind ; <i32> [#uses=0]
%tmp1 = tail call i32 (...)* @bork( ) nounwind ; <i32> [#uses=0]
%tmp2 = tail call i32 (...)* @bork( ) nounwind ; <i32> [#uses=1]
%tmp3 = icmp eq i32 %tmp2, 0 ; <i1> [#uses=1]
br i1 %tmp3, label %bb7, label %bb5
bb5: ; preds = %bb
%tmp6 = tail call i32 (...)* @bork( ) nounwind ; <i32> [#uses=0]
br label %bb7
bb7: ; preds = %bb5, %bb
%tmp8 = tail call i32 (...)* @bork( ) nounwind ; <i32> [#uses=0]
%tmp9 = tail call i32 (...)* @bork( ) nounwind ; <i32> [#uses=0]
%tmp11 = icmp eq i32 %x.0, 37 ; <i1> [#uses=1]
br i1 %tmp11, label %bb14, label %bb16
bb14: ; preds = %bb7
%tmp15 = tail call i32 (...)* @bar( ) nounwind ; <i32> [#uses=0]
br label %bb16
bb16: ; preds = %bb14, %bb7
%tmp17 = tail call i32 (...)* @zap( ) nounwind ; <i32> [#uses=1]
%indvar.next = add i32 %i.0, 1 ; <i32> [#uses=2]
%exitcond = icmp eq i32 %indvar.next, 42 ; <i1> [#uses=1]
br i1 %exitcond, label %return, label %somebb
somebb:
br label %bb
return: ; preds = %bb16
ret void
}
declare i32 @bork(...)
declare i32 @bar(...)
declare i32 @zap(...)