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Teach InstructionSimplify about phi nodes. I chose to have it simply

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offload the work to hasConstantValue rather than do something more
complicated (such handling mutually recursive phis) because (1) it is
not clear it is worth it; and (2) if it is worth it, maybe such logic
would be better placed in hasConstantValue.  Adjust some GVN tests
which are now cleaned up much further (eg: all phi nodes are removed).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119043 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2010-11-14 13:30:18 +00:00
parent c0362d5c6e
commit cd6636c737
4 changed files with 24 additions and 22 deletions
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2
lib/Analysis/InstructionSimplify.cpp
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@ -699,6 +699,8 @@ Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) {
SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
return SimplifyGEPInst(&Ops[0], Ops.size(), TD);
}
case Instruction::PHI:
return cast<PHINode>(I)->hasConstantValue();
}
}

5
lib/Transforms/InstCombine/InstCombinePHI.cpp
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@ -12,6 +12,7 @@
//===----------------------------------------------------------------------===//
#include "InstCombine.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Target/TargetData.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/STLExtras.h"
@ -731,8 +732,8 @@ Instruction *InstCombiner::SliceUpIllegalIntegerPHI(PHINode &FirstPhi) {
Instruction *InstCombiner::visitPHINode(PHINode &PN) {
// If LCSSA is around, don't mess with Phi nodes
if (MustPreserveLCSSA) return 0;
if (Value *V = PN.hasConstantValue())
if (Value *V = SimplifyInstruction(&PN, TD))
return ReplaceInstUsesWith(PN, V);
// If all PHI operands are the same operation, pull them through the PHI,

29
test/Transforms/GVN/2007-07-26-InterlockingLoops.ll
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@ -1,30 +1,33 @@
; RUN: opt < %s -basicaa -gvn -S | grep {tmp17625.* = phi i32. }
; RUN: opt < %s -basicaa -gvn -S | grep {tmp17631.* = phi i32. }
; RUN: opt < %s -basicaa -gvn -S | FileCheck %s
@last = external global [65 x i32*] ; <[65 x i32*]*> [#uses=1]
@last = external global [65 x i32*]
define i32 @NextRootMove(i32 %wtm) {
cond_next95: ; preds = %cond_true85, %cond_true79, %cond_true73, %bb68
%tmp17618 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4 ; <i32*> [#uses=0]
entry:
%tmp17618 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4
; CHECK: entry:
; CHECK-NEXT: %tmp17618 = load
; CHECK-NOT: load
; CHECK-NOT: phi
br label %cond_true116
cond_true116: ; preds = %cond_true111
cond_true116:
br i1 false, label %cond_true128, label %cond_true145
cond_true128: ; preds = %cond_true121
%tmp17625 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4 ; <i32*> [#uses=0]
cond_true128:
%tmp17625 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4
br i1 false, label %bb98.backedge, label %return.loopexit
bb98.backedge: ; preds = %bb171, %cond_true145, %cond_true128
bb98.backedge:
br label %cond_true116
cond_true145: ; preds = %cond_false
%tmp17631 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4 ; <i32*> [#uses=0]
cond_true145:
%tmp17631 = load i32** getelementptr ([65 x i32*]* @last, i32 0, i32 1), align 4
br i1 false, label %bb98.backedge, label %return.loopexit
return.loopexit: ; preds = %bb171, %cond_true145, %cond_true128
return.loopexit:
br label %return
return: ; preds = %return.loopexit, %cond_next95, %cond_true85
return:
ret i32 0
}

10
test/Transforms/GVN/2010-03-31-RedundantPHIs.ll
View File

@ -1,5 +1,8 @@
; RUN: opt < %s -basicaa -gvn -S | FileCheck %s
; CHECK-NOT: load
; CHECK-NOT: phi
define i8* @cat(i8* %s1, ...) nounwind {
entry:
br i1 undef, label %bb, label %bb3
@ -29,18 +32,11 @@ bb10: ; preds = %bb8
br label %bb11
bb11: ; preds = %bb10, %bb9
; CHECK: bb11:
; CHECK: phi
; CHECK-NOT: phi
br label %bb12
bb12: ; preds = %bb11, %bb6
; CHECK: bb12:
; CHECK: phi
; CHECK-NOT: phi
br i1 undef, label %bb8, label %bb13
bb13: ; preds = %bb12
; CHECK: bb13:
ret i8* undef
}