From: Vitaly Buka Date: Fri, 12 Jul 2019 17:21:55 +0000 (+0000) Subject: CodeGet: Init 32bit pointers with 0xFFFFFFFF X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=378f8bc374c51bffd29c0e6f93711c6ca9a4f55b;p=clang 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 git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@365921 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/CodeGen/PatternInit.cpp b/lib/CodeGen/PatternInit.cpp index 7a1baf96cf..3410c7f215 100644 --- a/lib/CodeGen/PatternInit.cpp +++ b/lib/CodeGen/PatternInit.cpp @@ -17,12 +17,13 @@ llvm::Constant *clang::CodeGen::initializationPatternFor(CodeGenModule &CGM, // 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::initializationPatternFor(CodeGenModule &CGM, 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( 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); } diff --git a/test/CodeGenCXX/auto-var-init.cpp b/test/CodeGenCXX/auto-var-init.cpp index 0bfe6c34a9..bb52d04b01 100644 --- a/test/CodeGenCXX/auto-var-init.cpp +++ b/test/CodeGenCXX/auto-var-init.cpp @@ -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