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Prevent hoisting fmul from THEN/ELSE to IF if there is fmsub/fmadd opportunity.

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This patch adds the isProfitableToHoist API.  For AArch64, we want to prevent a
fmul from being hoisted in cases where it is more profitable to form a
fmsub/fmadd.

Phabricator Review: http://reviews.llvm.org/D7299
Patch by Lawrence Hu <lawrence@codeaurora.org>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230241 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chad Rosier
2015-02-23 19:15:16 +00:00
parent 3986322604
commit 6229219f7e
10 changed files with 134 additions and 2 deletions
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8
lib/Transforms/Utils/SimplifyCFG.cpp
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@@ -1053,7 +1053,8 @@ static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I);
/// HoistThenElseCodeToIf - Given a conditional branch that goes to BB1 and
/// BB2, hoist any common code in the two blocks up into the branch block. The
/// caller of this function guarantees that BI's block dominates BB1 and BB2.
static bool HoistThenElseCodeToIf(BranchInst *BI, const DataLayout *DL) {
static bool HoistThenElseCodeToIf(BranchInst *BI, const DataLayout *DL,
const TargetTransformInfo &TTI) {
// This does very trivial matching, with limited scanning, to find identical
// instructions in the two blocks. In particular, we don't want to get into
// O(M*N) situations here where M and N are the sizes of BB1 and BB2. As
@@ -1088,6 +1089,9 @@ static bool HoistThenElseCodeToIf(BranchInst *BI, const DataLayout *DL) {
if (isa<TerminatorInst>(I1))
goto HoistTerminator;
if (!TTI.isProfitableToHoist(I1) || !TTI.isProfitableToHoist(I2))
return Changed;
// For a normal instruction, we just move one to right before the branch,
// then replace all uses of the other with the first. Finally, we remove
// the now redundant second instruction.
@@ -4442,7 +4446,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
// can hoist it up to the branching block.
if (BI->getSuccessor(0)->getSinglePredecessor()) {
if (BI->getSuccessor(1)->getSinglePredecessor()) {
if (HoistThenElseCodeToIf(BI, DL))
if (HoistThenElseCodeToIf(BI, DL, TTI))
return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true;
} else {
// If Successor #1 has multiple preds, we may be able to conditionally