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[InlineCost] Don't add the soft float function call cost for the fneg idiom, fsub -0.0, %x

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Summary: Fneg can be implemented with an xor rather than a function call so we don't need to add the function call overhead. This was pointed out in D62699

Reviewers: efriedma, cameron.mcinally

Reviewed By: efriedma

Subscribers: javed.absar, eraman, hiraditya, haicheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62747

llvm-svn: 362304
This commit is contained in:
Craig Topper 2019-06-01 19:40:07 +00:00
parent faf43294f9
commit 2f065dbf77
2 changed files with 30 additions and 2 deletions
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7
lib/Analysis/InlineCost.cpp
View File

@ -35,6 +35,7 @@
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
@ -1095,9 +1096,11 @@ bool CallAnalyzer::visitBinaryOperator(BinaryOperator &I) {
// If the instruction is floating point, and the target says this operation
// is expensive, this may eventually become a library call. Treat the cost
// as such.
// as such. Unless it's fneg which can be implemented with an xor.
using namespace llvm::PatternMatch;
if (I.getType()->isFloatingPointTy() &&
TTI.getFPOpCost(I.getType()) == TargetTransformInfo::TCC_Expensive)
TTI.getFPOpCost(I.getType()) == TargetTransformInfo::TCC_Expensive &&
!match(&I, m_FNeg(m_Value())))
addCost(InlineConstants::CallPenalty);
return false;

25
test/Transforms/Inline/ARM/inline-fp.ll
View File

@ -12,6 +12,8 @@
; NOFP-DAG: double not inlined into test_double because too costly to inline (cost=125, threshold=75)
; NOFP-DAG: single_force_soft not inlined into test_single_force_soft because too costly to inline (cost=125, threshold=75)
; NOFP-DAG: single_force_soft not inlined into test_single_force_soft because too costly to inline (cost=125, threshold=75)
; NOFP-DAG: single_force_soft_fneg not inlined into test_single_force_soft_fneg because too costly to inline (cost=100, threshold=75)
; NOFP-DAG: single_force_soft_fneg not inlined into test_single_force_soft_fneg because too costly to inline (cost=100, threshold=75)
; FULLFP-DAG: single inlined into test_single with (cost=0, threshold=75)
; FULLFP-DAG: single inlined into test_single with (cost=-15000, threshold=75)
@ -21,6 +23,8 @@
; FULLFP-DAG: double inlined into test_double with (cost=-15000, threshold=75)
; FULLFP-DAG: single_force_soft not inlined into test_single_force_soft because too costly to inline (cost=125, threshold=75)
; FULLFP-DAG: single_force_soft not inlined into test_single_force_soft because too costly to inline (cost=125, threshold=75)
; FULLFP-DAG: single_force_soft_fneg not inlined into test_single_force_soft_fneg because too costly to inline (cost=100, threshold=75)
; FULLFP-DAG: single_force_soft_fneg not inlined into test_single_force_soft_fneg because too costly to inline (cost=100, threshold=75)
; SINGLEFP-DAG: single inlined into test_single with (cost=0, threshold=75)
; SINGLEFP-DAG: single inlined into test_single with (cost=-15000, threshold=75)
@ -30,6 +34,8 @@
; SINGLEFP-DAG: double not inlined into test_double because too costly to inline (cost=125, threshold=75)
; SINGLEFP-DAG: single_force_soft not inlined into test_single_force_soft because too costly to inline (cost=125, threshold=75)
; SINGLEFP-DAG: single_force_soft not inlined into test_single_force_soft because too costly to inline (cost=125, threshold=75)
; SINGLEFP-DAG: single_force_soft_fneg not inlined into test_single_force_soft_fneg because too costly to inline (cost=100, threshold=75)
; SINGLEFP-DAG: single_force_soft_fneg not inlined into test_single_force_soft_fneg because too costly to inline (cost=100, threshold=75)
define i32 @test_single(i32 %a, i8 %b, i32 %c, i8 %d) #0 {
%call = call float @single(i32 %a, i8 zeroext %b)
@ -55,6 +61,12 @@ define i32 @test_single_force_soft(i32 %a, i8 %b, i32 %c, i8 %d) #1 {
ret i32 0
}
define i32 @test_single_force_soft_fneg(i32 %a, i8 %b, i32 %c, i8 %d) #1 {
%call = call float @single_force_soft_fneg(i32 %a, i8 zeroext %b) #1
%call2 = call float @single_force_soft_fneg(i32 %c, i8 zeroext %d) #1
ret i32 0
}
define internal float @single(i32 %response, i8 zeroext %value1) #0 {
entry:
%conv = zext i8 %value1 to i32
@ -106,6 +118,19 @@ entry:
ret float %div
}
define internal float @single_force_soft_fneg(i32 %response, i8 zeroext %value1) #1 {
entry:
%conv = zext i8 %value1 to i32
%sub = add nsw i32 %conv, -1
%conv1 = sitofp i32 %sub to float
%0 = tail call float @llvm.pow.f32(float 0x3FF028F5C0000000, float %conv1)
%mul = fsub float -0.0, %0
%conv2 = sitofp i32 %response to float
%sub3 = fsub float %conv2, %mul
%div = fdiv float %sub3, %mul
ret float %div
}
declare float @llvm.pow.f32(float, float) optsize minsize
declare double @llvm.pow.f64(double, double) optsize minsize