RPCS3/llvm
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm.git synced 2024-12-26 14:15:53 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

allow pushing icmps through phis with multiple uses and across critical edges.

Browse Source 
These are important to push up to encourage jump threading.  This shrinks 176.gcc a bit.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82923 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-09-27 20:46:36 +00:00
parent c6df8f4d5f
commit 213cd61fa7
1 changed files with 23 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -388,7 +388,11 @@ namespace {
// which has a PHI node as operand #0, see if we can fold the instruction
// into the PHI (which is only possible if all operands to the PHI are
// constants).
Instruction *FoldOpIntoPhi(Instruction &I);
//
// If AllowAggressive is true, FoldOpIntoPhi will allow certain transforms
// that would normally be unprofitable because they strongly encourage jump
// threading.
Instruction *FoldOpIntoPhi(Instruction &I, bool AllowAggressive = false);
// FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
// operator and they all are only used by the PHI, PHI together their
@ -1942,11 +1946,22 @@ static Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
/// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which
/// has a PHI node as operand #0, see if we can fold the instruction into the
/// PHI (which is only possible if all operands to the PHI are constants).
Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) {
///
/// If AllowAggressive is true, FoldOpIntoPhi will allow certain transforms
/// that would normally be unprofitable because they strongly encourage jump
/// threading.
Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I,
bool AllowAggressive) {
AllowAggressive = false;
PHINode *PN = cast<PHINode>(I.getOperand(0));
unsigned NumPHIValues = PN->getNumIncomingValues();
if (!PN->hasOneUse() || NumPHIValues == 0) return 0;
if (NumPHIValues == 0 ||
// We normally only transform phis with a single use, unless we're trying
// hard to make jump threading happen.
(!PN->hasOneUse() && !AllowAggressive))
return 0;
// Check to see if all of the operands of the PHI are simple constants
// (constantint/constantfp/undef). If there is one non-constant value,
// remember the BB it is in. If there is more than one or if *it* is a PHI,
@ -1970,7 +1985,7 @@ Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) {
// operation in that block. However, if this is a critical edge, we would be
// inserting the computation one some other paths (e.g. inside a loop). Only
// do this if the pred block is unconditionally branching into the phi block.
if (NonConstBB) {
if (NonConstBB != 0 && !AllowAggressive) {
BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator());
if (!BI || !BI->isUnconditional()) return 0;
}
@ -5865,7 +5880,7 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
// 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))
if (Instruction *NV = FoldOpIntoPhi(I, true))
return NV;
break;
case Instruction::SIToFP:
@ -6221,11 +6236,11 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
break;
case Instruction::PHI:
// Only fold icmp into the PHI if the phi and fcmp are in the same
// Only fold icmp into the PHI if the phi and icmp 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))
if (Instruction *NV = FoldOpIntoPhi(I, true))
return NV;
break;
case Instruction::Select: {