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Recommit "[InlineCost] Use TTI to check if GEP is free." 

This recommits r292526 which is reverted in r292529 after fixing the test case.

The original summary:

Currently, a GEP is considered free only if its indices are all constant.
TTI::getGEPCost() can give target-specific more accurate analysis. TTI is
already used for the cost of many other instructions.

llvm-svn: 292570
This commit is contained in:
Haicheng Wu 2017-01-20 03:09:11 +00:00
parent f002264d49
commit 1af1f071ea
2 changed files with 48 additions and 2 deletions
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20
llvm/lib/Analysis/InlineCost.cpp
View File

@ -134,6 +134,7 @@ class CallAnalyzer : public InstVisitor<CallAnalyzer, bool> {
void accumulateSROACost(DenseMap<Value *, int>::iterator CostIt,
int InstructionCost);
bool isGEPOffsetConstant(GetElementPtrInst &GEP);
bool isGEPFree(GetElementPtrInst &GEP);
bool accumulateGEPOffset(GEPOperator &GEP, APInt &Offset);
bool simplifyCallSite(Function *F, CallSite CS);
ConstantInt *stripAndComputeInBoundsConstantOffsets(Value *&V);
@ -331,6 +332,21 @@ bool CallAnalyzer::accumulateGEPOffset(GEPOperator &GEP, APInt &Offset) {
return true;
}
/// \brief Use TTI to check whether a GEP is free.
///
/// Respects any simplified values known during the analysis of this callsite.
bool CallAnalyzer::isGEPFree(GetElementPtrInst &GEP) {
SmallVector<Value *, 4> Indices;
for (User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end(); I != E; ++I)
if (Constant *SimpleOp = SimplifiedValues.lookup(*I))
Indices.push_back(SimpleOp);
else
Indices.push_back(*I);
return TargetTransformInfo::TCC_Free ==
TTI.getGEPCost(GEP.getSourceElementType(), GEP.getPointerOperand(),
Indices);
}
bool CallAnalyzer::visitAlloca(AllocaInst &I) {
// Check whether inlining will turn a dynamic alloca into a static
// alloca and handle that case.
@ -396,7 +412,7 @@ bool CallAnalyzer::visitGetElementPtr(GetElementPtrInst &I) {
// Non-constant GEPs aren't folded, and disable SROA.
if (SROACandidate)
disableSROA(CostIt);
return false;
return isGEPFree(I);
}
// Add the result as a new mapping to Base + Offset.
@ -422,7 +438,7 @@ bool CallAnalyzer::visitGetElementPtr(GetElementPtrInst &I) {
// Variable GEPs will require math and will disable SROA.
if (SROACandidate)
disableSROA(CostIt);
return false;
return isGEPFree(I);
}
bool CallAnalyzer::visitBitCast(BitCastInst &I) {

30
llvm/test/Transforms/Inline/gep-cost.ll Normal file
View File

@ -0,0 +1,30 @@
; REQUIRES: asserts
; RUN: opt -inline < %s -mtriple=aarch64--linux-gnu -mcpu=kryo -S -debug-only=inline-cost 2>&1 | FileCheck %s
target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
target triple = "aarch64--linux-gnu"
define void @outer([4 x i32]* %ptr, i32 %i) {
call void @inner1([4 x i32]* %ptr, i32 %i)
call void @inner2([4 x i32]* %ptr, i32 %i)
ret void
}
; The gep in inner1() is reg+reg, which is a legal addressing mode for AArch64.
; Thus, both the gep and ret can be simplified.
; CHECK: Analyzing call of inner1
; CHECK: NumInstructionsSimplified: 2
; CHECK: NumInstructions: 2
define void @inner1([4 x i32]* %ptr, i32 %i) {
%G = getelementptr inbounds [4 x i32], [4 x i32]* %ptr, i32 0, i32 %i
ret void
}
; The gep in inner2() is reg+imm+reg, which is not a legal addressing mode for
; AArch64. Thus, only the ret can be simplified and not the gep.
; CHECK: Analyzing call of inner2
; CHECK: NumInstructionsSimplified: 1
; CHECK: NumInstructions: 2
define void @inner2([4 x i32]* %ptr, i32 %i) {
%G = getelementptr inbounds [4 x i32], [4 x i32]* %ptr, i32 1, i32 %i
ret void
}