Author: vitalybuka
Date: Fri Jul 12 10:21:55 2019
New Revision: 365921
URL: http://llvm.org/viewvc/llvm-project?rev=365921&view=rev
Log:
CodeGet: Init 32bit pointers with 0xFFFFFFFF
Summary:
Patch makes D63967 effective for 32bit platforms and improves pattern
initialization there. It cuts size of 32bit binary compiled with
-ftrivial-auto-var-init=pattern by 2% (3% with -Os).
Binary size change on CTMark, (with -fuse-ld=lld -Wl,--icf=all, similar results
with default linker options)
```
master patch diff
Os pattern 7.915580e+05 7.698424e+05 -0.028387
O3 pattern 9.953688e+05 9.752952e+05 -0.019325
```
Zero vs Pattern on master
```
zero pattern diff
Os 7.689712e+05 7.915580e+05 0.031380
O3 9.744796e+05 9.953688e+05 0.021133
```
Zero vs Pattern with the patch
```
zero pattern diff
Os 7.689712e+05 7.698424e+05 0.000789
O3 9.744796e+05 9.752952e+05 0.000742
```
Reviewers: pcc, eugenis, glider, jfb
Reviewed By: jfb
Subscribers: hubert.reinterpretcast, dexonsmith, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D64597
Modified:
cfe/trunk/lib/CodeGen/PatternInit.cpp
cfe/trunk/test/CodeGenCXX/auto-var-init.cpp
Modified: cfe/trunk/lib/CodeGen/PatternInit.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/PatternInit.cpp?rev=365921&r1=365920&r2=365921&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/PatternInit.cpp (original)
+++ cfe/trunk/lib/CodeGen/PatternInit.cpp Fri Jul 12 10:21:55 2019
@@ -17,12 +17,13 @@ llvm::Constant *clang::CodeGen::initiali
// repeated byte-pattern which makes it easier to synthesize. We use it for
// pointers as well as integers so that aggregates are likely to be
// initialized with this repeated value.
- constexpr uint64_t LargeValue = 0xAAAAAAAAAAAAAAAAull;
// For 32-bit platforms it's a bit trickier because, across systems, only the
- // zero page can reasonably be expected to be unmapped, and even then we need
- // a very low address. We use a smaller value, and that value sadly doesn't
- // have a repeated byte-pattern. We don't use it for integers.
- constexpr uint32_t SmallValue = 0x000000AA;
+ // zero page can reasonably be expected to be unmapped. We use max 0xFFFFFFFF
+ // assuming that memory access will overlap into zero page.
+ const uint64_t IntValue =
+ CGM.getContext().getTargetInfo().getMaxPointerWidth() < 64
+ ? 0xFFFFFFFFFFFFFFFFull
+ : 0xAAAAAAAAAAAAAAAAull;
// Floating-point values are initialized as NaNs because they propagate.
Using
// a repeated byte pattern means that it will be easier to initialize
// all-floating-point aggregates and arrays with memset. Further, aggregates
@@ -36,27 +37,18 @@ llvm::Constant *clang::CodeGen::initiali
Ty->isVectorTy() ? Ty->getVectorElementType() : Ty)
->getBitWidth();
if (BitWidth <= 64)
- return llvm::ConstantInt::get(Ty, LargeValue);
+ return llvm::ConstantInt::get(Ty, IntValue);
return llvm::ConstantInt::get(
- Ty, llvm::APInt::getSplat(BitWidth, llvm::APInt(64, LargeValue)));
+ Ty, llvm::APInt::getSplat(BitWidth, llvm::APInt(64, IntValue)));
}
if (Ty->isPtrOrPtrVectorTy()) {
auto *PtrTy = cast<llvm::PointerType>(
Ty->isVectorTy() ? Ty->getVectorElementType() : Ty);
unsigned PtrWidth = CGM.getContext().getTargetInfo().getPointerWidth(
PtrTy->getAddressSpace());
- llvm::Type *IntTy = llvm::IntegerType::get(CGM.getLLVMContext(), PtrWidth);
- uint64_t IntValue;
- switch (PtrWidth) {
- default:
+ if (PtrWidth > 64)
llvm_unreachable("pattern initialization of unsupported pointer width");
- case 64:
- IntValue = LargeValue;
- break;
- case 32:
- IntValue = SmallValue;
- break;
- }
+ llvm::Type *IntTy = llvm::IntegerType::get(CGM.getLLVMContext(), PtrWidth);
auto *Int = llvm::ConstantInt::get(IntTy, IntValue);
return llvm::ConstantExpr::getIntToPtr(Int, PtrTy);
}
Modified: cfe/trunk/test/CodeGenCXX/auto-var-init.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/auto-var-init.cpp?rev=365921&r1=365920&r2=365921&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/auto-var-init.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/auto-var-init.cpp Fri Jul 12 10:21:55 2019
@@ -12,7 +12,7 @@
#ifdef __x86_64__
char inits[] =
{"-86/-21846/-1431655766/i64/-6148914691236517206/-6148914691236517206/i128/-113427455640312821154458202477256070486/i64/-6148914691236517206/AA/"};
#else
-char inits[] =
{"-86/-21846/-1431655766/i32/-1431655766/-6148914691236517206/i32/-1431655766/i32/170/AA/"};
+char inits[] = {"-1/-1/-1/i32/-1/-1/i32/-1/i32/-1/FF/"};
#define __int128 int;
#endif
// PATTERN: @inits = {{.*}}
c"[[I8:[^/]+]]/[[I16:[^/]+]]/[[I32:[^/]+]]/[[ILONGT:[^/]+]]/[[ILONG:[^/]+]]/[[I64:[^/]+]]/[[I128T:[^/]+]]/[[I128:[^/]+]]/[[IPTRT:[^/]+]]/[[IPTR:[^/]+]]/[[IC:[^/]+]]/\00",
align 1
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