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[LICM] Sinking doesn't involve the preheader

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PR23608 pointed out that using the preheader to gain a context instruction isn't always legal because a loop might not have a preheader.  When looking into that, I realized that using the preheader to determine legality for sinking is questionable at best.  Given no test covers that case and the original commit didn't seem to intend it, I restructured the code to only ask context sensative queries for hoising of loads and stores.  This is effectively a partial revert of 237593.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237985 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Philip Reames 2015-05-22 02:14:05 +00:00
parent 253c092e56
commit 2c78f9499c
2 changed files with 61 additions and 5 deletions
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16
lib/Transforms/Scalar/LICM.cpp
View File

@ -84,7 +84,8 @@ static bool isSafeToExecuteUnconditionally(const Instruction &Inst,
const DominatorTree *DT,
const TargetLibraryInfo *TLI,
const Loop *CurLoop,
const LICMSafetyInfo *SafetyInfo);
const LICMSafetyInfo *SafetyInfo,
const Instruction *CtxI = nullptr);
static bool pointerInvalidatedByLoop(Value *V, uint64_t Size,
const AAMDNodes &AAInfo,
AliasSetTracker *CurAST);
@ -388,7 +389,8 @@ bool llvm::hoistRegion(DomTreeNode *N, AliasAnalysis *AA, LoopInfo *LI,
//
if (CurLoop->hasLoopInvariantOperands(&I) &&
canSinkOrHoistInst(I, AA, DT, TLI, CurLoop, CurAST, SafetyInfo) &&
isSafeToExecuteUnconditionally(I, DT, TLI, CurLoop, SafetyInfo))
isSafeToExecuteUnconditionally(I, DT, TLI, CurLoop, SafetyInfo,
CurLoop->getLoopPreheader()->getTerminator()))
Changed |= hoist(I, CurLoop->getLoopPreheader());
}
@ -487,7 +489,11 @@ bool canSinkOrHoistInst(Instruction &I, AliasAnalysis *AA, DominatorTree *DT,
!isa<InsertValueInst>(I))
return false;
return isSafeToExecuteUnconditionally(I, DT, TLI, CurLoop, SafetyInfo);
// TODO: Plumb the context instruction through to make hoisting and sinking
// more powerful. Hoisting of loads already works due to the special casing
// above.
return isSafeToExecuteUnconditionally(I, DT, TLI, CurLoop, SafetyInfo,
nullptr);
}
/// Returns true if a PHINode is a trivially replaceable with an
@ -647,8 +653,8 @@ static bool isSafeToExecuteUnconditionally(const Instruction &Inst,
const DominatorTree *DT,
const TargetLibraryInfo *TLI,
const Loop *CurLoop,
const LICMSafetyInfo *SafetyInfo) {
const Instruction *CtxI = CurLoop->getLoopPreheader()->getTerminator();
const LICMSafetyInfo *SafetyInfo,
const Instruction *CtxI) {
if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT, TLI))
return true;

50
test/Transforms/LICM/pr23608.ll Normal file
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@ -0,0 +1,50 @@
; RUN: opt -S -licm %s | FileCheck %s
; ModuleID = '../pr23608.ll'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
%struct.PyFrameObject = type { i32 }
@a = common global %struct.PyFrameObject* null, align 8
@__msan_origin_tls = external thread_local(initialexec) global i32
define void @fn1() {
entry:
br label %indirectgoto
while.cond: ; preds = %indirectgoto, %bb15
%tmp = load %struct.PyFrameObject*, %struct.PyFrameObject** @a, align 8
%_msld = load i64, i64* inttoptr (i64 and (i64 ptrtoint (%struct.PyFrameObject** @a to i64), i64 -70368744177665) to i64*), align 8
%tmp1 = load i32, i32* inttoptr (i64 add (i64 and (i64 ptrtoint (%struct.PyFrameObject** @a to i64), i64 -70368744177665), i64 35184372088832) to i32*), align 8
%f_iblock = getelementptr inbounds %struct.PyFrameObject, %struct.PyFrameObject* %tmp, i64 0, i32 0
br label %bb2
bb: ; preds = %while.cond
call void @__msan_warning_noreturn()
unreachable
bb2: ; preds = %while.cond
%tmp3 = load i32, i32* %f_iblock, align 4
%tmp4 = ptrtoint i32* %f_iblock to i64
%tmp8 = inttoptr i64 %tmp4 to i32*
%tobool = icmp eq i64 %tmp4, 0
br i1 %tobool, label %bb13, label %bb15
bb13: ; preds = %bb2
; CHECK-LABEL bb13:
; CHECK: %tmp8.le = inttoptr
%.lcssa7 = phi i32* [ %tmp8, %bb2 ]
call void @__msan_warning_noreturn()
unreachable
bb15: ; preds = %bb2
br i1 %tobool, label %while.end, label %while.cond
while.end: ; preds = %bb15
ret void
indirectgoto: ; preds = %indirectgoto, %entry
indirectbr i8* null, [label %indirectgoto, label %while.cond]
}
declare void @__msan_warning_noreturn()